From: Dennis Zhou <dennis@kernel.org>
To: Dennis Zhou <dennis@kernel.org>, Tejun Heo <tj@kernel.org>,
Christoph Lameter <cl@linux.com>
Cc: Vlad Buslov <vladbu@mellanox.com>,
kernel-team@fb.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: [PATCH 00/12] introduce percpu block scan_hint
Date: Wed, 27 Feb 2019 21:18:27 -0500 [thread overview]
Message-ID: <20190228021839.55779-1-dennis@kernel.org> (raw)
Hi everyone,
It was reported a while [1] that an increase in allocation alignment
requirement [2] caused the percpu memory allocator to do significantly
more work.
After spending quite a bit of time diving into it, it seems the crux was
the following:
1) chunk management by free_bytes caused allocations to scan over
chunks that could not fit due to fragmentation
2) per block fragmentation required scanning from an early first_free
bit causing allocations to repeat work
This series introduces a scan_hint for pcpu_block_md and merges the
paths used to manage the hints. The scan_hint represents the largest
known free area prior to the contig_hint. There are some caveats to
this. First, it may not necessarily be the largest area as we do partial
updates based on freeing of regions and failed scanning in
pcpu_alloc_area(). Second, if contig_hint == scan_hint, then
scan_hint_start > contig_hint_start is possible. This is necessary
for scan_hint discovery when refreshing the hint of a block.
A necessary change is to enforce a block to be the size of a page. This
let's the management of nr_empty_pop_pages to be done by breaking and
making full contig_hints in the hint update paths. Prior, this was done
by piggy backing off of refreshing the chunk contig_hint as it performed
a full scan and counting empty full pages.
The following are the results found using the workload provided in [3].
branch | time
------------------------
5.0-rc7 | 69s
[2] reverted | 44s
scan_hint | 39s
The times above represent the approximate average across multiple runs.
I tested based on a basic 1M 16-byte allocation pattern with no
alignment requirement and times did not differ between 5.0-rc7 and
scan_hint.
[1] https://lore.kernel.org/netdev/CANn89iKb_vW+LA-91RV=zuAqbNycPFUYW54w_S=KZ3HdcWPw6Q@mail.gmail.com/
[2] https://lore.kernel.org/netdev/20181116154329.247947-1-edumazet@google.com/
[3] https://lore.kernel.org/netdev/vbfzhrj9smb.fsf@mellanox.com/
This patchset contains the following 12 patches:
0001-percpu-update-free-path-with-correct-new-free-region.patch
0002-percpu-do-not-search-past-bitmap-when-allocating-an-.patch
0003-percpu-introduce-helper-to-determine-if-two-regions-.patch
0004-percpu-manage-chunks-based-on-contig_bits-instead-of.patch
0005-percpu-relegate-chunks-unusable-when-failing-small-a.patch
0006-percpu-set-PCPU_BITMAP_BLOCK_SIZE-to-PAGE_SIZE.patch
0007-percpu-add-block-level-scan_hint.patch
0008-percpu-remember-largest-area-skipped-during-allocati.patch
0009-percpu-use-block-scan_hint-to-only-scan-forward.patch
0010-percpu-make-pcpu_block_md-generic.patch
0011-percpu-convert-chunk-hints-to-be-based-on-pcpu_block.patch
0012-percpu-use-chunk-scan_hint-to-skip-some-scanning.patch
0001 fixes an issue where the chunk contig_hint was being updated
improperly with the new region's starting offset and possibly differing
contig_hint. 0002 fixes possibly scanning pass the end of the bitmap.
0003 introduces a helper to do region overlap comparison. 0004 switches
to chunk management by contig_hint rather than free_bytes. 0005 moves
chunks that fail to allocate to the empty block list to prevent excess
scanning with of chunks with small contig_hints and poor alignment.
0006 introduces the constraint PCPU_BITMAP_BLOCK_SIZE == PAGE_SIZE and
modifies nr_empty_pop_pages management to be a part of the hint updates.
0007-0009 introduces percpu block scan_hint. 0010 makes pcpu_block_md
generic so chunk hints can be managed as a pcpu_block_md responsible
for more bits. 0011-0012 add chunk scan_hints.
This patchset is on top of percpu#master a3b22b9f11d9.
diffstats below:
Dennis Zhou (12):
percpu: update free path with correct new free region
percpu: do not search past bitmap when allocating an area
percpu: introduce helper to determine if two regions overlap
percpu: manage chunks based on contig_bits instead of free_bytes
percpu: relegate chunks unusable when failing small allocations
percpu: set PCPU_BITMAP_BLOCK_SIZE to PAGE_SIZE
percpu: add block level scan_hint
percpu: remember largest area skipped during allocation
percpu: use block scan_hint to only scan forward
percpu: make pcpu_block_md generic
percpu: convert chunk hints to be based on pcpu_block_md
percpu: use chunk scan_hint to skip some scanning
include/linux/percpu.h | 12 +-
mm/percpu-internal.h | 15 +-
mm/percpu-km.c | 2 +-
mm/percpu-stats.c | 5 +-
mm/percpu.c | 547 +++++++++++++++++++++++++++++------------
5 files changed, 404 insertions(+), 177 deletions(-)
Thanks,
Dennis
next reply other threads:[~2019-02-28 2:18 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-28 2:18 Dennis Zhou [this message]
2019-02-28 2:18 ` [PATCH 01/12] percpu: update free path with correct new free region Dennis Zhou
2019-03-02 12:56 ` Peng Fan
2019-02-28 2:18 ` [PATCH 02/12] percpu: do not search past bitmap when allocating an area Dennis Zhou
2019-03-02 13:32 ` Peng Fan
2019-03-02 22:23 ` Dennis Zhou
2019-03-03 8:41 ` Peng Fan
2019-02-28 2:18 ` [PATCH 03/12] percpu: introduce helper to determine if two regions overlap Dennis Zhou
2019-03-02 13:37 ` Peng Fan
2019-03-02 22:24 ` Dennis Zhou
2019-02-28 2:18 ` [PATCH 04/12] percpu: manage chunks based on contig_bits instead of free_bytes Dennis Zhou
2019-03-02 13:48 ` Peng Fan
2019-03-02 22:32 ` Dennis Zhou
2019-03-03 8:42 ` Peng Fan
2019-02-28 2:18 ` [PATCH 05/12] percpu: relegate chunks unusable when failing small allocations Dennis Zhou
2019-03-02 13:55 ` Peng Fan
2019-03-02 22:34 ` Dennis Zhou
2019-02-28 2:18 ` [PATCH 06/12] percpu: set PCPU_BITMAP_BLOCK_SIZE to PAGE_SIZE Dennis Zhou
2019-03-03 4:56 ` Peng Fan
2019-02-28 2:18 ` [PATCH 07/12] percpu: add block level scan_hint Dennis Zhou
2019-03-03 6:01 ` Peng Fan
2019-03-03 20:23 ` Dennis Zhou
2019-03-04 9:36 ` Peng Fan
2019-02-28 2:18 ` [PATCH 08/12] percpu: remember largest area skipped during allocation Dennis Zhou
2019-02-28 2:18 ` [PATCH 09/12] percpu: use block scan_hint to only scan forward Dennis Zhou
2019-02-28 2:18 ` [PATCH 10/12] percpu: make pcpu_block_md generic Dennis Zhou
2019-03-03 6:35 ` Peng Fan
2019-02-28 2:18 ` [PATCH 11/12] percpu: convert chunk hints to be based on pcpu_block_md Dennis Zhou
2019-03-03 8:18 ` Peng Fan
2019-03-03 20:22 ` Dennis Zhou
2019-03-04 6:36 ` Peng Fan
2019-02-28 2:18 ` [PATCH 12/12] percpu: use chunk scan_hint to skip some scanning Dennis Zhou
2019-03-03 8:38 ` Peng Fan
2019-02-28 14:47 ` [PATCH 00/12] introduce percpu block scan_hint Vlad Buslov
2019-03-13 20:19 ` Dennis Zhou
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190228021839.55779-1-dennis@kernel.org \
--to=dennis@kernel.org \
--cc=cl@linux.com \
--cc=kernel-team@fb.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=tj@kernel.org \
--cc=vladbu@mellanox.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).