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Michal Hocko 09dbcf422e mm/sparse.c: do not waste pre allocated memmap space 
Vincent has noticed [1] that there is something unusual with the memmap
allocations going on on his platform

: I noticed this because on my ARM64 platform, with 1 GiB of memory the
: first [and only] section is allocated from the zeroing path while with
: 2 GiB of memory the first 1 GiB section is allocated from the
: non-zeroing path.

The underlying problem is that although sparse_buffer_init allocates
enough memory for all sections on the node sparse_buffer_alloc is not
able to consume them due to mismatch in the expected allocation
alignement.  While sparse_buffer_init preallocation uses the PAGE_SIZE
alignment the real memmap has to be aligned to section_map_size() this
results in a wasted initial chunk of the preallocated memmap and
unnecessary fallback allocation for a section.

While we are at it also change __populate_section_memmap to align to the
requested size because at least VMEMMAP has constrains to have memmap
properly aligned.

[1] http://lkml.kernel.org/r/20191030131122.8256-1-vincent.whitchurch@axis.com

[akpm@linux-foundation.org: tweak layout, per David]
Link: http://lkml.kernel.org/r/20191119092642.31799-1-mhocko@kernel.org
Fixes: 35fd1eb1e8 ("mm/sparse: abstract sparse buffer allocations")
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Debugged-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Oscar Salvador <OSalvador@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-12-01 12:59:05 -08:00
arch ARC: mm: remove __ARCH_USE_5LEVEL_HACK 2019-12-01 06:29:19 -08:00
block for-5.5/disk-revalidate-20191122 2019-11-25 11:37:01 -08:00
certs PKCS#7: Refactor verify_pkcs7_signature() 2019-08-05 18:40:18 -04:00
crypto Merge git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2019-11-25 19:49:58 -08:00
Documentation Documentation/admin-guide/cgroup-v2.rst: document why inactive_X + active_X may not equal X 2019-12-01 06:29:18 -08:00
drivers drivers/base/memory.c: drop the mem_sysfs_mutex 2019-12-01 12:59:04 -08:00
fs fs/direct-io.c: keep dio_warn_stale_pagecache() when CONFIG_BLOCK=n 2019-12-01 06:29:18 -08:00
include include/linux/memory_hotplug.h: move definitions of {set,clear}_zone_contiguous 2019-12-01 12:59:04 -08:00
init Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2019-11-25 20:02:57 -08:00
ipc ipc/sem.c: convert to use built-in RCU list checking 2019-09-25 17:51:41 -07:00
kernel mm/mmap.c: use IS_ERR_VALUE to check return value of get_unmapped_area 2019-12-01 06:29:19 -08:00
lib rss_stat: add support to detect RSS updates of external mm 2019-12-01 06:29:18 -08:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm mm/sparse.c: do not waste pre allocated memmap space 2019-12-01 12:59:05 -08:00
net for-5.5/io_uring-post-20191128 2019-11-28 10:43:39 -08:00
samples New tracing features: 2019-11-27 11:42:01 -08:00
scripts scripts/spelling.txt: add more spellings to spelling.txt 2019-12-01 06:29:17 -08:00
security drm main pull for 5.5-rc1 2019-11-27 17:45:48 -08:00
sound sound updates for 5.5-rc1 2019-11-26 20:04:35 -08:00
tools memfd: add test for COW on MAP_PRIVATE and F_SEAL_FUTURE_WRITE mappings 2019-12-01 12:59:03 -08:00
usr kbuild: update compile-test header list for v5.4-rc2 2019-10-05 15:29:49 +09:00
virt KVM: Fix jump label out_free_* in kvm_init() 2019-11-23 11:29:17 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Modules updates for v5.4 2019-09-22 10:34:46 -07:00
.mailmap Merge branch 'efi-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-11-26 14:52:11 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS: Remove Simon as Renesas SoC Co-Maintainer 2019-10-10 08:12:51 -07:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS \n 2019-11-30 11:34:33 -08:00
Makefile Linux 5.4 2019-11-24 16:32:01 -08:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.