For each page scheduled for compaction (e. g. by z3fold_free()), try to
apply inter-page compaction before running the traditional/ existing
intra-page compaction. That means, if the page has only one buddy, we
treat that buddy as a new object that we aim to place into an existing
z3fold page. If such a page is found, that object is transferred and the
old page is freed completely. The transferred object is named "foreign"
and treated slightly differently thereafter.
Namely, we increase "foreign handle" counter for the new page. Pages with
non-zero "foreign handle" count become unmovable. This patch implements
"foreign handle" detection when a handle is freed to decrement the foreign
handle counter accordingly, so a page may as well become movable again as
the time goes by.
As a result, we almost always have exactly 3 objects per page and
significantly better average compression ratio.
[cai@lca.pw: fix -Wunused-but-set-variable warnings]
Link: http://lkml.kernel.org/r/1570542062-29144-1-git-send-email-cai@lca.pw
[vitalywool@gmail.com: avoid subtle race when freeing slots]
Link: http://lkml.kernel.org/r/20191127152118.6314b99074b0626d4c5a8835@gmail.com
[vitalywool@gmail.com: compact objects more accurately]
Link: http://lkml.kernel.org/r/20191127152216.6ad33745a21ba71c53606acb@gmail.com
[vitalywool@gmail.com: protect handle reads]
Link: http://lkml.kernel.org/r/20191127152345.8059852f60947686674d726d@gmail.com
Link: http://lkml.kernel.org/r/20191006041457.24113-1-vitalywool@gmail.com
Signed-off-by: Vitaly Wool <vitaly.vul@sony.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Henry Burns <henrywolfeburns@gmail.com>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There's a really hard to reproduce race in z3fold between z3fold_free()
and z3fold_reclaim_page(). z3fold_reclaim_page() can claim the page
after z3fold_free() has checked if the page was claimed and
z3fold_free() will then schedule this page for compaction which may in
turn lead to random page faults (since that page would have been
reclaimed by then).
Fix that by claiming page in the beginning of z3fold_free() and not
forgetting to clear the claim in the end.
[vitalywool@gmail.com: v2]
Link: http://lkml.kernel.org/r/20190928113456.152742cf@bigdell
Link: http://lkml.kernel.org/r/20190926104844.4f0c6efa1366b8f5741eaba9@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Reported-by: Markus Linnala <markus.linnala@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Henry Burns <henrywolfeburns@gmail.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Markus Linnala <markus.linnala@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently there is a leak in init_z3fold_page() -- it allocates handles
from kmem cache even for headless pages, but then they are never used and
never freed, so eventually kmem cache may get exhausted. This patch
provides a fix for that.
Link: http://lkml.kernel.org/r/20190917185352.44cf285d3ebd9e64548de5de@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Reported-by: Markus Linnala <markus.linnala@gmail.com>
Tested-by: Markus Linnala <markus.linnala@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Henry Burns <henrywolfeburns@gmail.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
z3fold_page_reclaim()'s retry mechanism is broken: on a second iteration
it will have zhdr from the first one so that zhdr is no longer in line
with struct page. That leads to crashes when the system is stressed.
Fix that by moving zhdr assignment up.
While at it, protect against using already freed handles by using own
local slots structure in z3fold_page_reclaim().
Link: http://lkml.kernel.org/r/20190908162919.830388dc7404d1e2c80f4095@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Reported-by: Markus Linnala <markus.linnala@gmail.com>
Reported-by: Chris Murphy <bugzilla@colorremedies.com>
Reported-by: Agustin Dall'Alba <agustin@dallalba.com.ar>
Cc: "Maciej S. Szmigiero" <mail@maciej.szmigiero.name>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Henry Burns <henrywolfeburns@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
With the original commit applied, z3fold_zpool_destroy() may get blocked
on wait_event() for indefinite time. Revert this commit for the time
being to get rid of this problem since the issue the original commit
addresses is less severe.
Link: http://lkml.kernel.org/r/20190910123142.7a9c8d2de4d0acbc0977c602@gmail.com
Fixes: d776aaa989 ("mm/z3fold.c: fix race between migration and destruction")
Reported-by: Agustín Dall'Alba <agustin@dallalba.com.ar>
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Jonathan Adams <jwadams@google.com>
Cc: Henry Burns <henrywolfeburns@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In z3fold_destroy_pool() we call destroy_workqueue(&pool->compact_wq).
However, we have no guarantee that migration isn't happening in the
background at that time.
Migration directly calls queue_work_on(pool->compact_wq), if destruction
wins that race we are using a destroyed workqueue.
Link: http://lkml.kernel.org/r/20190809213828.202833-1-henryburns@google.com
Signed-off-by: Henry Burns <henryburns@google.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Jonathan Adams <jwadams@google.com>
Cc: Henry Burns <henrywolfeburns@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The constraint from the zpool use of z3fold_destroy_pool() is there are
no outstanding handles to memory (so no active allocations), but it is
possible for there to be outstanding work on either of the two wqs in
the pool.
Calling z3fold_deregister_migration() before the workqueues are drained
means that there can be allocated pages referencing a freed inode,
causing any thread in compaction to be able to trip over the bad pointer
in PageMovable().
Link: http://lkml.kernel.org/r/20190726224810.79660-2-henryburns@google.com
Fixes: 1f862989b0 ("mm/z3fold.c: support page migration")
Signed-off-by: Henry Burns <henryburns@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Jonathan Adams <jwadams@google.com>
Cc: Vitaly Vul <vitaly.vul@sony.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Henry Burns <henrywolfeburns@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The constraint from the zpool use of z3fold_destroy_pool() is there are
no outstanding handles to memory (so no active allocations), but it is
possible for there to be outstanding work on either of the two wqs in
the pool.
If there is work queued on pool->compact_workqueue when it is called,
z3fold_destroy_pool() will do:
z3fold_destroy_pool()
destroy_workqueue(pool->release_wq)
destroy_workqueue(pool->compact_wq)
drain_workqueue(pool->compact_wq)
do_compact_page(zhdr)
kref_put(&zhdr->refcount)
__release_z3fold_page(zhdr, ...)
queue_work_on(pool->release_wq, &pool->work) *BOOM*
So compact_wq needs to be destroyed before release_wq.
Link: http://lkml.kernel.org/r/20190726224810.79660-1-henryburns@google.com
Fixes: 5d03a66139 ("mm/z3fold.c: use kref to prevent page free/compact race")
Signed-off-by: Henry Burns <henryburns@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Jonathan Adams <jwadams@google.com>
Cc: Vitaly Vul <vitaly.vul@sony.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Al Viro <viro@zeniv.linux.org.uk
Cc: Henry Burns <henrywolfeburns@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull vfs mount updates from Al Viro:
"The first part of mount updates.
Convert filesystems to use the new mount API"
* 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (63 commits)
mnt_init(): call shmem_init() unconditionally
constify ksys_mount() string arguments
don't bother with registering rootfs
init_rootfs(): don't bother with init_ramfs_fs()
vfs: Convert smackfs to use the new mount API
vfs: Convert selinuxfs to use the new mount API
vfs: Convert securityfs to use the new mount API
vfs: Convert apparmorfs to use the new mount API
vfs: Convert openpromfs to use the new mount API
vfs: Convert xenfs to use the new mount API
vfs: Convert gadgetfs to use the new mount API
vfs: Convert oprofilefs to use the new mount API
vfs: Convert ibmasmfs to use the new mount API
vfs: Convert qib_fs/ipathfs to use the new mount API
vfs: Convert efivarfs to use the new mount API
vfs: Convert configfs to use the new mount API
vfs: Convert binfmt_misc to use the new mount API
convenience helper: get_tree_single()
convenience helper get_tree_nodev()
vfs: Kill sget_userns()
...
z3fold_page_migration() calls memcpy(new_zhdr, zhdr, PAGE_SIZE).
However, zhdr contains fields that can't be directly coppied over (ex:
list_head, a circular linked list). We only need to initialize the
linked lists in new_zhdr, as z3fold_isolate_page() already ensures that
these lists are empty
Additionally it is possible that zhdr->work has been placed in a
workqueue. In this case we shouldn't migrate the page, as zhdr->work
references zhdr as opposed to new_zhdr.
Link: http://lkml.kernel.org/r/20190716000520.230595-1-henryburns@google.com
Fixes: 1f862989b0 ("mm/z3fold.c: support page migration")
Signed-off-by: Henry Burns <henryburns@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Vitaly Vul <vitaly.vul@sony.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: Jonathan Adams <jwadams@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
z3fold_page_migrate() will never succeed because it attempts to acquire
a lock that has already been taken by migrate.c in __unmap_and_move().
__unmap_and_move() migrate.c
trylock_page(oldpage)
move_to_new_page(oldpage_newpage)
a_ops->migrate_page(oldpage, newpage)
z3fold_page_migrate(oldpage, newpage)
trylock_page(oldpage)
Link: http://lkml.kernel.org/r/20190710213238.91835-1-henryburns@google.com
Fixes: 1f862989b0 ("mm/z3fold.c: support page migration")
Signed-off-by: Henry Burns <henryburns@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: Vitaly Vul <vitaly.vul@sony.com>
Cc: Jonathan Adams <jwadams@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Snild Dolkow <snild@sony.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
One of the gfp flags used to show that a page is movable is
__GFP_HIGHMEM. Currently z3fold_alloc() fails when __GFP_HIGHMEM is
passed. Now that z3fold pages are movable, we allow __GFP_HIGHMEM. We
strip the movability related flags from the call to kmem_cache_alloc()
for our slots since it is a kernel allocation.
[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20190712222118.108192-1-henryburns@google.com
Signed-off-by: Henry Burns <henryburns@google.com>
Acked-by: Vitaly Wool <vitalywool@gmail.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
As reported by Henry Burns:
Running z3fold stress testing with address sanitization showed zhdr->slots
was being used after it was freed.
z3fold_free(z3fold_pool, handle)
free_handle(handle)
kmem_cache_free(pool->c_handle, zhdr->slots)
release_z3fold_page_locked_list(kref)
__release_z3fold_page(zhdr, true)
zhdr_to_pool(zhdr)
slots_to_pool(zhdr->slots) *BOOM*
To fix this, add pointer to the pool back to z3fold_header and modify
zhdr_to_pool to return zhdr->pool.
Link: http://lkml.kernel.org/r/20190708134808.e89f3bfadd9f6ffd7eff9ba9@gmail.com
Fixes: 7c2b8baa61 ("mm/z3fold.c: add structure for buddy handles")
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Reported-by: Henry Burns <henryburns@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Jonathan Adams <jwadams@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Following zsmalloc.c's example we call trylock_page() and unlock_page().
Also make z3fold_page_migrate() assert that newpage is passed in locked,
as per the documentation.
[akpm@linux-foundation.org: fix trylock_page return value test, per Shakeel]
Link: http://lkml.kernel.org/r/20190702005122.41036-1-henryburns@google.com
Link: http://lkml.kernel.org/r/20190702233538.52793-1-henryburns@google.com
Signed-off-by: Henry Burns <henryburns@google.com>
Suggested-by: Vitaly Wool <vitalywool@gmail.com>
Acked-by: Vitaly Wool <vitalywool@gmail.com>
Acked-by: David Rientjes <rientjes@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Vitaly Vul <vitaly.vul@sony.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Xidong Wang <wangxidong_97@163.com>
Cc: Jonathan Adams <jwadams@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
kmem_cache_alloc() may be called from z3fold_alloc() in atomic context, so
we need to pass correct gfp flags to avoid "scheduling while atomic" bug.
Link: http://lkml.kernel.org/r/20190523153245.119dfeed55927e8755250ddd@gmail.com
Fixes: 7c2b8baa61 ("mm/z3fold.c: add structure for buddy handles")
Signed-off-by: Vitaly Wool <vitaly.vul@sony.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Convert the zsfold filesystem to the new internal mount API as the old one
will be obsoleted and removed. This allows greater flexibility in
communication of mount parameters between userspace, the VFS and the
filesystem.
See Documentation/filesystems/mount_api.txt for more information.
Signed-off-by: David Howells <dhowells@redhat.com>
Once upon a time we used to set ->d_name of e.g. pipefs root
so that d_path() on pipes would work. These days it's
completely pointless - dentries of pipes are not even connected
to pipefs root. However, mount_pseudo() had set the root
dentry name (passed as the second argument) and callers
kept inventing names to pass to it. Including those that
didn't *have* any non-root dentries to start with...
All of that had been pointless for about 8 years now; it's
time to get rid of that cargo-culting...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Add SPDX license identifiers to all files which:
- Have no license information of any form
- Have MODULE_LICENCE("GPL*") inside which was used in the initial
scan/conversion to ignore the file
These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:
GPL-2.0-only
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Now that we are not using page address in handles directly, we can make
z3fold pages movable to decrease the memory fragmentation z3fold may
create over time.
This patch starts advertising non-headless z3fold pages as movable and
uses the existing kernel infrastructure to implement moving of such pages
per memory management subsystem's request. It thus implements 3 required
callbacks for page migration:
* isolation callback: z3fold_page_isolate(): try to isolate the page by
removing it from all lists. Pages scheduled for some activity and
mapped pages will not be isolated. Return true if isolation was
successful or false otherwise
* migration callback: z3fold_page_migrate(): re-check critical
conditions and migrate page contents to the new page provided by the
memory subsystem. Returns 0 on success or negative error code otherwise
* putback callback: z3fold_page_putback(): put back the page if
z3fold_page_migrate() for it failed permanently (i. e. not with
-EAGAIN code).
[lkp@intel.com: z3fold_page_isolate() can be static]
Link: http://lkml.kernel.org/r/20190419130924.GA161478@ivb42
Link: http://lkml.kernel.org/r/20190417103922.31253da5c366c4ebe0419cfc@gmail.com
Signed-off-by: Vitaly Wool <vitaly.vul@sony.com>
Signed-off-by: kbuild test robot <lkp@intel.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
Cc: Uladzislau Rezki <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
For z3fold to be able to move its pages per request of the memory
subsystem, it should not use direct object addresses in handles. Instead,
it will create abstract handles (3 per page) which will contain pointers
to z3fold objects. Thus, it will be possible to change these pointers
when z3fold page is moved.
Link: http://lkml.kernel.org/r/20190417103826.484eaf18c1294d682769880f@gmail.com
Signed-off-by: Vitaly Wool <vitaly.vul@sony.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
Cc: Uladzislau Rezki <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The current z3fold implementation only searches this CPU's page lists for
a fitting page to put a new object into. This patch adds quick search for
very well fitting pages (i. e. those having exactly the required number
of free space) on other CPUs too, before allocating a new page for that
object.
Link: http://lkml.kernel.org/r/20190417103733.72ae81abe1552397c95a008e@gmail.com
Signed-off-by: Vitaly Wool <vitaly.vul@sony.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
Cc: Uladzislau Rezki <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "z3fold: support page migration", v2.
This patchset implements page migration support and slightly better buddy
search. To implement page migration support, z3fold has to move away from
the current scheme of handle encoding. i. e. stop encoding page address
in handles. Instead, a small per-page structure is created which will
contain actual addresses for z3fold objects, while pointers to fields of
that structure will be used as handles.
Thus, it will be possible to change the underlying addresses to reflect
page migration.
To support migration itself, 3 callbacks will be implemented:
1: isolation callback: z3fold_page_isolate(): try to isolate the page
by removing it from all lists. Pages scheduled for some activity and
mapped pages will not be isolated. Return true if isolation was
successful or false otherwise
2: migration callback: z3fold_page_migrate(): re-check critical
conditions and migrate page contents to the new page provided by the
system. Returns 0 on success or negative error code otherwise
3: putback callback: z3fold_page_putback(): put back the page if
z3fold_page_migrate() for it failed permanently (i. e. not with
-EAGAIN code).
To make sure an isolated page doesn't get freed, its kref is incremented
in z3fold_page_isolate() and decremented during post-migration compaction,
if migration was successful, or by z3fold_page_putback() in the other
case.
Since the new handle encoding scheme implies slight memory consumption
increase, better buddy search (which decreases memory consumption) is
included in this patchset.
This patch (of 4):
Introduce a separate helper function for object allocation, as well as 2
smaller helpers to add a buddy to the list and to get a pointer to the
pool from the z3fold header. No functional changes here.
Link: http://lkml.kernel.org/r/20190417103633.a4bb770b5bf0fb7e43ce1666@gmail.com
Signed-off-by: Vitaly Wool <vitaly.vul@sony.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
Cc: Uladzislau Rezki <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Reclaim and free can race on an object which is basically fine but in
order for reclaim to be able to map "freed" object we need to encode
object length in the handle. handle_to_chunks() is then introduced to
extract object length from a handle and use it during mapping.
Moreover, to avoid racing on a z3fold "headless" page release, we should
not try to free that page in z3fold_free() if the reclaim bit is set.
Also, in the unlikely case of trying to reclaim a page being freed, we
should not proceed with that page.
While at it, fix the page accounting in reclaim function.
This patch supersedes "[PATCH] z3fold: fix reclaim lock-ups".
Link: http://lkml.kernel.org/r/20181105162225.74e8837d03583a9b707cf559@gmail.com
Signed-off-by: Vitaly Wool <vitaly.vul@sony.com>
Signed-off-by: Jongseok Kim <ks77sj@gmail.com>
Reported-by-by: Jongseok Kim <ks77sj@gmail.com>
Reviewed-by: Snild Dolkow <snild@sony.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Do not try to optimize in-page object layout while the page is under
reclaim. This fixes lock-ups on reclaim and improves reclaim
performance at the same time.
[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20180430125800.444cae9706489f412ad12621@gmail.com
Signed-off-by: Vitaly Wool <vitaly.vul@sony.com>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Cc: <Oleksiy.Avramchenko@sony.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We have a perfectly good macro to determine whether the gfp flags allow
you to sleep or not; use it instead of trying to infer it.
Link: http://lkml.kernel.org/r/20180408062206.GC16007@bombadil.infradead.org
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Vitaly Wool <vitalywool@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In z3fold_create_pool(), the memory allocated by __alloc_percpu() is not
released on the error path that pool->compact_wq , which holds the
return value of create_singlethread_workqueue(), is NULL. This will
result in a memory leak bug.
[akpm@linux-foundation.org: fix oops on kzalloc() failure, check __alloc_percpu() retval]
Link: http://lkml.kernel.org/r/1522803111-29209-1-git-send-email-wangxidong_97@163.com
Signed-off-by: Xidong Wang <wangxidong_97@163.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently if z3fold couldn't find an unbuddied page it would first try
to pull a page off the stale list. The problem with this approach is
that we can't 100% guarantee that the page is not processed by the
workqueue thread at the same time unless we run cancel_work_sync() on
it, which we can't do if we're in an atomic context. So let's just
limit stale list usage to non-atomic contexts only.
Link: http://lkml.kernel.org/r/47ab51e7-e9c1-d30e-ab17-f734dbc3abce@gmail.com
Signed-off-by: Vitaly Vul <vitaly.vul@sony.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: <Oleksiy.Avramchenko@sony.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There are several places where parameter descriptions do no match the
actual code. Fix it.
Link: http://lkml.kernel.org/r/1516700871-22279-3-git-send-email-rppt@linux.vnet.ibm.com
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There is a race in the current z3fold implementation between
do_compact() called in a work queue context and the page release
procedure when page's kref goes to 0.
do_compact() may be waiting for page lock, which is released by
release_z3fold_page_locked right before putting the page onto the
"stale" list, and then the page may be freed as do_compact() modifies
its contents.
The mechanism currently implemented to handle that (checking the
PAGE_STALE flag) is not reliable enough. Instead, we'll use page's kref
counter to guarantee that the page is not released if its compaction is
scheduled. It then becomes compaction function's responsibility to
decrease the counter and quit immediately if the page was actually
freed.
Link: http://lkml.kernel.org/r/20171117092032.00ea56f42affbed19f4fcc6c@gmail.com
Signed-off-by: Vitaly Wool <vitaly.wool@sonymobile.com>
Cc: <Oleksiy.Avramchenko@sony.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix the situation when clear_bit() is called for page->private before
the page pointer is actually assigned. While at it, remove work_busy()
check because it is costly and does not give 100% guarantee anyway.
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: <Oleksiy.Avramchenko@sony.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
It is possible that on a (partially) unsuccessful page reclaim,
kref_put() called in z3fold_reclaim_page() does not yield page release,
but the page is released shortly afterwards by another thread. Then
z3fold_reclaim_page() would try to list_add() that (released) page again
which is obviously a bug.
To avoid that, spin_lock() has to be taken earlier, before the
kref_put() call mentioned earlier.
Link: http://lkml.kernel.org/r/20170913162937.bfff21c7d12b12a5f47639fd@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: <Oleksiy.Avramchenko@sony.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
It's been noted that z3fold doesn't scale well when it's run in a large
number of threads on many cores, which can be easily reproduced with fio
'randrw' test with --numjobs=32. E.g. the result for 1 cluster (4 cores)
is:
Run status group 0 (all jobs):
READ: io=244785MB, aggrb=496883KB/s, minb=15527KB/s, ...
WRITE: io=246735MB, aggrb=500841KB/s, minb=15651KB/s, ...
While for 8 cores (2 clusters) the result is:
Run status group 0 (all jobs):
READ: io=244785MB, aggrb=265942KB/s, minb=8310KB/s, ...
WRITE: io=246735MB, aggrb=268060KB/s, minb=8376KB/s, ...
The bottleneck here is the pool lock which many threads become waiting
upon. To reduce that spin lock contention, z3fold can operate only on
the lists local to the current CPU whenever possible. Due to the nature
of z3fold unbuddied list handling (it only takes the first entry off the
list on a hot path), if the z3fold pool is big enough and balanced well
enough, limiting search to only local unbuddied list doesn't lead to a
significant compression ratio degrade (2.57x vs 2.65x in our
measurements).
This patch also introduces two worker threads: one for async in-page
object layout optimization and one for releasing freed pages. This is
done to speed up z3fold_free() which is often on a hot path.
The fio results for 8-core case are now the following:
Run status group 0 (all jobs):
READ: io=244785MB, aggrb=1568.3MB/s, minb=50182KB/s, ...
WRITE: io=246735MB, aggrb=1580.8MB/s, minb=50582KB/s, ...
So we're in for almost 6x performance increase.
Link: http://lkml.kernel.org/r/20170806181443.f9b65018f8bde25ef990f9e8@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Stress testing of the current z3fold implementation on a 8-core system
revealed it was possible that a z3fold page deleted from its unbuddied
list in z3fold_alloc() would be put on another unbuddied list by
z3fold_free() while z3fold_alloc() is still processing it. This has
been introduced with commit 5a27aa822 ("z3fold: add kref refcounting")
due to the removal of special handling of a z3fold page not on any list
in z3fold_free().
To fix this, the z3fold page lock should be taken in z3fold_alloc()
before the pool lock is released. To avoid deadlocking, we just try to
lock the page as soon as we get a hold of it, and if trylock fails, we
drop this page and take the next one.
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: <Oleksiy.Avramchenko@sony.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commmit 5a27aa8220 ("z3fold: add kref refcounting") introduced a bug
in z3fold_reclaim_page() with function exit that may leave pool->lock
spinlock held. Here comes the trivial fix.
Fixes: 5a27aa8220 ("z3fold: add kref refcounting")
Link: http://lkml.kernel.org/r/20170311222239.7b83d8e7ef1914e05497649f@gmail.com
Reported-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
With both coming and already present locking optimizations, introducing
kref to reference-count z3fold objects is the right thing to do.
Moreover, it makes buddied list no longer necessary, and allows for a
simpler handling of headless pages.
[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20170131214650.8ea78033d91ded233f552bc0@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Reviewed-by: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Most of z3fold operations are in-page, such as modifying z3fold page
header or moving z3fold objects within a page. Taking per-pool spinlock
to protect per-page objects is therefore suboptimal, and the idea of
having a per-page spinlock (or rwlock) has been around for some time.
This patch implements spinlock-based per-page locking mechanism which is
lightweight enough to normally fit ok into the z3fold header.
Link: http://lkml.kernel.org/r/20170131214438.433e0a5fda908337b63206d3@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Reviewed-by: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
z3fold_compact_page() currently only handles the situation when there's
a single middle chunk within the z3fold page. However it may be worth
it to move middle chunk closer to either first or last chunk, whichever
is there, if the gap between them is big enough.
This patch adds the relevant code, using BIG_CHUNK_GAP define as a
threshold for middle chunk to be worth moving.
Link: http://lkml.kernel.org/r/20170131214334.c4f3eac9a477af0fa9a22c46@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Reviewed-by: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently the whole kernel build will be stopped if the size of struct
z3fold_header is greater than the size of one chunk, which is 64 bytes
by default. This patch instead defines the offset for z3fold objects as
the size of the z3fold header in chunks.
Fixed also are the calculation of num_free_chunks() and the address to
move the middle chunk to in case of in-page compaction in
z3fold_compact_page().
Link: http://lkml.kernel.org/r/20170131214057.d98677032bc7b1c6c59a80c9@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Reviewed-by: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
At present, Tying the first_num size to NCHUNKS_ORDER is confusing. the
number of chunks is completely unrelated to the number of buddies.
The patch limits the first_num to actual range of possible buddy indexes.
and that is more reasonable and obvious without functional change.
Link: http://lkml.kernel.org/r/1476776569-29504-1-git-send-email-zhongjiang@huawei.com
Signed-off-by: zhong jiang <zhongjiang@huawei.com>
Suggested-by: Dan Streetman <ddstreet@ieee.org>
Acked-by: Dan Streetman <ddstreet@ieee.org>
Acked-by: Vitaly Wool <vitalywool@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix erroneous z3fold header access in a HEADLESS page in reclaim
function, and change one remaining direct handle-to-buddy conversion to
use the appropriate helper.
Link: http://lkml.kernel.org/r/5748706F.9020208@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Reviewed-by: Dan Streetman <ddstreet@ieee.org>
Cc: Seth Jennings <sjenning@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch introduces z3fold, a special purpose allocator for storing
compressed pages. It is designed to store up to three compressed pages
per physical page. It is a ZBUD derivative which allows for higher
compression ratio keeping the simplicity and determinism of its
predecessor.
This patch comes as a follow-up to the discussions at the Embedded Linux
Conference in San-Diego related to the talk [1]. The outcome of these
discussions was that it would be good to have a compressed page
allocator as stable and deterministic as zbud with with higher
compression ratio.
To keep the determinism and simplicity, z3fold, just like zbud, always
stores an integral number of compressed pages per page, but it can store
up to 3 pages unlike zbud which can store at most 2. Therefore the
compression ratio goes to around 2.6x while zbud's one is around 1.7x.
The patch is based on the latest linux.git tree.
This version has been updated after testing on various simulators (e.g.
ARM Versatile Express, MIPS Malta, x86_64/Haswell) and basing on
comments from Dan Streetman [3].
[1] https://openiotelc2016.sched.org/event/6DAC/swapping-and-embedded-compression-relieves-the-pressure-vitaly-wool-softprise-consulting-ou
[2] https://lkml.org/lkml/2016/4/21/799
[3] https://lkml.org/lkml/2016/5/4/852
Link: http://lkml.kernel.org/r/20160509151753.ec3f9fda3c9898d31ff52a32@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
