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Filename Latest commit message Latest commit date
David Rientjes ddbf369c0a mm, vmacache: hash addresses based on pmd
When perf profiling a wide variety of different workloads, it was found
that vmacache_find() had higher than expected cost: up to 0.08% of cpu
utilization in some cases.  This was found to rival other core VM
functions such as alloc_pages_vma() with thp enabled and default
mempolicy, and the conditionals in __get_vma_policy().

VMACACHE_HASH() determines which of the four per-task_struct slots a vma
is cached for a particular address.  This currently depends on the pfn,
so pfn 5212 occupies a different vmacache slot than its neighboring pfn
5213.

vmacache_find() iterates through all four of current's vmacache slots
when looking up an address.  Hashing based on pfn, an address has
~1/VMACACHE_SIZE chance of being cached in the first vmacache slot, or
about 25%, *if* the vma is cached.

This patch hashes an address by its pmd instead of pte to optimize for
workloads with good spatial locality.  This results in a higher
probability of vmas being cached in the first slot that is checked:
normally ~70% on the same workloads instead of 25%.

[rientjes@google.com: various updates]
  Link: http://lkml.kernel.org/r/alpine.DEB.2.21.1807231532290.109445@chino.kir.corp.google.com
Link: http://lkml.kernel.org/r/alpine.DEB.2.21.1807091749150.114630@chino.kir.corp.google.com
Signed-off-by: David Rientjes <rientjes@google.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-17 16:20:32 -07:00
arch kernel/dma: remove unsupported gfp_mask parameter from dma_alloc_from_contiguous() 2018-08-17 16:20:32 -07:00
block
certs Replace magic for trusting the secondary keyring with #define 2018-08-16 09:57:20 -07:00
crypto Replace magic for trusting the secondary keyring with #define 2018-08-16 09:57:20 -07:00
Documentation tools/vm/page-types.c: add support for idle page tracking 2018-08-17 16:20:28 -07:00
drivers kernel/dma: remove unsupported gfp_mask parameter from dma_alloc_from_contiguous() 2018-08-17 16:20:32 -07:00
firmware
fs mm: add SHRINK_EMPTY shrinker methods return value 2018-08-17 16:20:31 -07:00
include mm, vmacache: hash addresses based on pmd 2018-08-17 16:20:32 -07:00
init mm: introduce CONFIG_MEMCG_KMEM as combination of CONFIG_MEMCG && !CONFIG_SLOB 2018-08-17 16:20:30 -07:00
ipc Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2018-08-15 15:04:25 -07:00
kernel kernel/dma: remove unsupported gfp_mask parameter from dma_alloc_from_contiguous() 2018-08-17 16:20:32 -07:00
lib SCSI misc on 20180815 2018-08-15 22:06:26 -07:00
LICENSES
mm mm, vmacache: hash addresses based on pmd 2018-08-17 16:20:32 -07:00
net Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2018-08-15 16:01:47 -07:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2018-08-15 15:04:25 -07:00
scripts scripts: add Python 3 compatibility to spdxcheck.py 2018-08-17 16:20:27 -07:00
security Merge branch 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2018-08-15 22:54:12 -07:00
sound ALSA: update dell-wmi mic-mute registration to new world order 2018-08-15 19:08:10 -07:00
tools tools/vm/page-types.c: add support for idle page tracking 2018-08-17 16:20:28 -07:00
usr
virt
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS 9p: remove Ron Minnich from MAINTAINERS 2018-08-17 16:20:26 -07:00
Kbuild
Kconfig
MAINTAINERS 9p: add Dominique Martinet to MAINTAINERS 2018-08-17 16:20:27 -07:00
Makefile Kconfig updates for v4.19 2018-08-15 12:50:10 -07:00
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.
See Documentation/00-INDEX for a list of what is contained in each file.

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.