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Bharata B Rao 045ab8c948 mm/slub: let number of online CPUs determine the slub page order
The page order of the slab that gets chosen for a given slab cache depends
on the number of objects that can be fit in the slab while meeting other
requirements.  We start with a value of minimum objects based on
nr_cpu_ids that is driven by possible number of CPUs and hence could be
higher than the actual number of CPUs present in the system.  This leads
to calculate_order() chosing a page order that is on the higher side
leading to increased slab memory consumption on systems that have bigger
page sizes.

Hence rely on the number of online CPUs when determining the mininum
objects, thereby increasing the chances of chosing a lower conservative
page order for the slab.

Vlastimil said:
  "Ideally, we would react to hotplug events and update existing caches
   accordingly. But for that, recalculation of order for existing caches
   would have to be made safe, while not affecting hot paths. We have
   removed the sysfs interface with 32a6f409b6 ("mm, slub: remove
   runtime allocation order changes") as it didn't seem easy and worth
   the trouble.

   In case somebody wants to start with a large order right from the
   boot because they know they will hotplug lots of cpus later, they can
   use slub_min_objects= boot param to override this heuristic. So in
   case this change regresses somebody's performance, there's a way
   around it and thus the risk is low IMHO"

Link: https://lkml.kernel.org/r/20201118082759.1413056-1-bharata@linux.ibm.com
Signed-off-by: Bharata B Rao <bharata@linux.ibm.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Roman Gushchin <guro@fb.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-12-15 12:13:38 -08:00
arch arch/Kconfig: fix spelling mistakes 2020-12-15 12:13:37 -08:00
block block-5.10-2020-12-05 2020-12-05 14:45:30 -08:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto drivers-5.10-2020-10-12 2020-10-13 13:04:41 -07:00
Documentation mm: slab: provide krealloc_array() 2020-12-15 12:13:37 -08:00
drivers dma-buf: use krealloc_array() 2020-12-15 12:13:37 -08:00
fs ocfs2: ratelimit the 'max lookup times reached' notice 2020-12-15 12:13:37 -08:00
include mm: slab: provide krealloc_array() 2020-12-15 12:13:37 -08:00
init initramfs: fix clang build failure 2020-12-11 14:02:14 -08:00
ipc ipc: adjust proc_ipc_sem_dointvec definition to match prototype 2020-09-05 12:14:29 -07:00
kernel kthread_worker: document CPU hotplug handling 2020-12-15 12:13:36 -08:00
lib selftest/fpu: avoid clang warning 2020-12-11 14:02:14 -08:00
LICENSES LICENSES/deprecated: add Zlib license text 2020-09-16 14:33:49 +02:00
mm mm/slub: let number of online CPUs determine the slub page order 2020-12-15 12:13:38 -08:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf 2020-12-10 14:29:30 -08:00
samples Tracing fixes for 5.10-rc6 2020-12-01 15:30:18 -08:00
scripts Kbuild fixes for v5.10 (2nd) 2020-12-06 10:31:39 -08:00
security selinux/stable-5.10 PR 20201113 2020-11-14 12:04:02 -08:00
sound ALSA: pcm: use krealloc_array() 2020-12-15 12:13:37 -08:00
tools Bugfixes for ARM, x86 and tools. 2020-12-12 10:08:16 -08:00
usr Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
virt kvm: x86/mmu: Support dirty logging for the TDP MMU 2020-10-23 03:42:13 -04:00
.clang-format RDMA 5.10 pull request 2020-10-17 11:18:18 -07:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: docs: ignore sphinx_*/ directories 2020-09-10 10:44:31 -06:00
.mailmap mailmap: add two more addresses of Uwe Kleine-König 2020-12-06 10:19:07 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Jason Cooper to CREDITS 2020-11-30 10:20:34 +01:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-12-10 15:30:13 -08:00
Makefile Linux 5.10 2020-12-13 14:41:30 -08:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.