The previous patch enables page migration of ksm pages, but that soon gets
into trouble: not surprising, since we're using the ksm page lock to lock
operations on its stable_node, but page migration switches the page whose
lock is to be used for that. Another layer of locking would fix it, but
do we need that yet?
Do we actually need page migration of ksm pages? Yes, memory hotremove
needs to offline sections of memory: and since we stopped allocating ksm
pages with GFP_HIGHUSER, they will tend to be GFP_HIGHUSER_MOVABLE
candidates for migration.
But KSM is currently unconscious of NUMA issues, happily merging pages
from different NUMA nodes: at present the rule must be, not to use
MADV_MERGEABLE where you care about NUMA. So no, NUMA page migration of
ksm pages does not make sense yet.
So, to complete support for ksm swapping we need to make hotremove safe.
ksm_memory_callback() take ksm_thread_mutex when MEM_GOING_OFFLINE and
release it when MEM_OFFLINE or MEM_CANCEL_OFFLINE. But if mapped pages
are freed before migration reaches them, stable_nodes may be left still
pointing to struct pages which have been removed from the system: the
stable_node needs to identify a page by pfn rather than page pointer, then
it can safely prune them when MEM_OFFLINE.
And make NUMA migration skip PageKsm pages where it skips PageReserved.
But it's only when we reach unmap_and_move() that the page lock is taken
and we can be sure that raised pagecount has prevented a PageAnon from
being upgraded: so add offlining arg to migrate_pages(), to migrate ksm
page when offlining (has sufficient locking) but reject it otherwise.
Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Izik Eidus <ieidus@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Chris Wright <chrisw@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
#ifdef in *.c file decrease source readability a bit. removing is better.
This patch doesn't have any functional change.
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
On large memory systems, the VM can spend way too much time scanning
through pages that it cannot (or should not) evict from memory. Not only
does it use up CPU time, but it also provokes lock contention and can
leave large systems under memory presure in a catatonic state.
This patch series improves VM scalability by:
1) putting filesystem backed, swap backed and unevictable pages
onto their own LRUs, so the system only scans the pages that it
can/should evict from memory
2) switching to two handed clock replacement for the anonymous LRUs,
so the number of pages that need to be scanned when the system
starts swapping is bound to a reasonable number
3) keeping unevictable pages off the LRU completely, so the
VM does not waste CPU time scanning them. ramfs, ramdisk,
SHM_LOCKED shared memory segments and mlock()ed VMA pages
are keept on the unevictable list.
This patch:
isolate_lru_page logically belongs to be in vmscan.c than migrate.c.
It is tough, because we don't need that function without memory migration
so there is a valid argument to have it in migrate.c. However a
subsequent patch needs to make use of it in the core mm, so we can happily
move it to vmscan.c.
Also, make the function a little more generic by not requiring that it
adds an isolated page to a given list. Callers can do that.
Note that we now have '__isolate_lru_page()', that does
something quite different, visible outside of vmscan.c
for use with memory controller. Methinks we need to
rationalize these names/purposes. --lts
[akpm@linux-foundation.org: fix mm/memory_hotplug.c build]
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We'd like to support CONFIG_MEMORY_HOTREMOVE on s390, which depends on
CONFIG_MIGRATION. So far, CONFIG_MIGRATION is only available with NUMA
support.
This patch makes CONFIG_MIGRATION selectable for architectures that define
ARCH_ENABLE_MEMORY_HOTREMOVE. When MIGRATION is enabled w/o NUMA, the
kernel won't compile because migrate_vmas() does not know about
vm_ops->migrate() and vma_migratable() does not know about policy_zone.
To fix this, those two functions can be restricted to '#ifdef CONFIG_NUMA'
because they are not being used w/o NUMA. vma_migratable() is moved over
from migrate.h to mempolicy.h.
[kosaki.motohiro@jp.fujitsu.com: build fix]
Acked-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: KOSAKI Motorhiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Address spaces contain an allocation flag that specifies restriction on the
zone for pages placed in the mapping. I.e. some device may require pages
to be allocated from a DMA zone. Block devices may not be able to use
pages from HIGHMEM.
Memory policies and the common use of page migration works only on the
highest zone. If the address space does not allow allocation from the
highest zone then the pages in the address space are not migratable simply
because we can only allocate memory for a specified node if we allow
allocation for the highest zone on each node.
Acked-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently we do not check for vma flags if sys_move_pages is called to move
individual pages. If sys_migrate_pages is called to move pages then we
check for vm_flags that indicate a non migratable vma but that still
includes VM_LOCKED and we can migrate mlocked pages.
Extract the vma_migratable check from mm/mempolicy.c, fix it and put it
into migrate.h so that is can be used from both locations.
Problem was spotted by Lee Schermerhorn
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Hooks for calling vma specific migration functions
With this patch a vma may define a vma->vm_ops->migrate function. That
function may perform page migration on its own (some vmas may not contain page
structs and therefore cannot be handled by regular page migration. Pages in a
vma may require special preparatory treatment before migration is possible
etc) . Only mmap_sem is held when the migration function is called. The
migrate() function gets passed two sets of nodemasks describing the source and
the target of the migration. The flags parameter either contains
MPOL_MF_MOVE which means that only pages used exclusively by
the specified mm should be moved
or
MPOL_MF_MOVE_ALL which means that pages shared with other processes
should also be moved.
The migration function returns 0 on success or an error condition. An error
condition will prevent regular page migration from occurring.
On its own this patch cannot be included since there are no users for this
functionality. But it seems that the uncached allocator will need this
functionality at some point.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
move_pages() is used to move individual pages of a process. The function can
be used to determine the location of pages and to move them onto the desired
node. move_pages() returns status information for each page.
long move_pages(pid, number_of_pages_to_move,
addresses_of_pages[],
nodes[] or NULL,
status[],
flags);
The addresses of pages is an array of void * pointing to the
pages to be moved.
The nodes array contains the node numbers that the pages should be moved
to. If a NULL is passed instead of an array then no pages are moved but
the status array is updated. The status request may be used to determine
the page state before issuing another move_pages() to move pages.
The status array will contain the state of all individual page migration
attempts when the function terminates. The status array is only valid if
move_pages() completed successfullly.
Possible page states in status[]:
0..MAX_NUMNODES The page is now on the indicated node.
-ENOENT Page is not present
-EACCES Page is mapped by multiple processes and can only
be moved if MPOL_MF_MOVE_ALL is specified.
-EPERM The page has been mlocked by a process/driver and
cannot be moved.
-EBUSY Page is busy and cannot be moved. Try again later.
-EFAULT Invalid address (no VMA or zero page).
-ENOMEM Unable to allocate memory on target node.
-EIO Unable to write back page. The page must be written
back in order to move it since the page is dirty and the
filesystem does not provide a migration function that
would allow the moving of dirty pages.
-EINVAL A dirty page cannot be moved. The filesystem does not provide
a migration function and has no ability to write back pages.
The flags parameter indicates what types of pages to move:
MPOL_MF_MOVE Move pages that are only mapped by the process.
MPOL_MF_MOVE_ALL Also move pages that are mapped by multiple processes.
Requires sufficient capabilities.
Possible return codes from move_pages()
-ENOENT No pages found that would require moving. All pages
are either already on the target node, not present, had an
invalid address or could not be moved because they were
mapped by multiple processes.
-EINVAL Flags other than MPOL_MF_MOVE(_ALL) specified or an attempt
to migrate pages in a kernel thread.
-EPERM MPOL_MF_MOVE_ALL specified without sufficient priviledges.
or an attempt to move a process belonging to another user.
-EACCES One of the target nodes is not allowed by the current cpuset.
-ENODEV One of the target nodes is not online.
-ESRCH Process does not exist.
-E2BIG Too many pages to move.
-ENOMEM Not enough memory to allocate control array.
-EFAULT Parameters could not be accessed.
A test program for move_pages() may be found with the patches
on ftp.kernel.org:/pub/linux/kernel/people/christoph/pmig/patches-2.6.17-rc4-mm3
From: Christoph Lameter <clameter@sgi.com>
Detailed results for sys_move_pages()
Pass a pointer to an integer to get_new_page() that may be used to
indicate where the completion status of a migration operation should be
placed. This allows sys_move_pags() to report back exactly what happened to
each page.
Wish there would be a better way to do this. Looks a bit hacky.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Jes Sorensen <jes@trained-monkey.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Andi Kleen <ak@muc.de>
Cc: Michael Kerrisk <mtk-manpages@gmx.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Instead of passing a list of new pages, pass a function to allocate a new
page. This allows the correct placement of MPOL_INTERLEAVE pages during page
migration. It also further simplifies the callers of migrate pages.
migrate_pages() becomes similar to migrate_pages_to() so drop
migrate_pages_to(). The batching of new page allocations becomes unnecessary.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Jes Sorensen <jes@trained-monkey.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Do not leave pages on the lists passed to migrate_pages(). Seems that we will
not need any postprocessing of pages. This will simplify the handling of
pages by the callers of migrate_pages().
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Jes Sorensen <jes@trained-monkey.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Change handling of address spaces.
Pass a pointer to the address space in which the page is migrated to all
migration function. This avoids repeatedly having to retrieve the address
space pointer from the page and checking it for validity. The old page
mapping will change once migration has gone to a certain step, so it is less
confusing to have the pointer always available.
Move the setting of the mapping and index for the new page into
migrate_pages().
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Remove the export for migrate_page_remove_references() and migrate_page_copy()
that are unlikely to be used directly by filesystems implementing migration.
The export was useful when buffer_migrate_page() lived in fs/buffer.c but it
has now been moved to migrate.c in the migration reorg.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Centralize the page migration functions in anticipation of additional
tinkering. Creates a new file mm/migrate.c
1. Extract buffer_migrate_page() from fs/buffer.c
2. Extract central migration code from vmscan.c
3. Extract some components from mempolicy.c
4. Export pageout() and remove_from_swap() from vmscan.c
5. Make it possible to configure NUMA systems without page migration
and non-NUMA systems with page migration.
I had to so some #ifdeffing in mempolicy.c that may need a cleanup.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
