linux-kernel - [PATCH for-next v3 0/3] implement pcpu bio caching for IRQ I/O

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Date:   Fri, 21 Oct 2022 11:34:04 +0100
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org
Cc:     io-uring@...r.kernel.org, linux-kernel@...r.kernel.org,
        Christoph Hellwig <hch@....de>,
        Pavel Begunkov <asml.silence@...il.com>
Subject: [PATCH for-next v3 0/3] implement pcpu bio caching for IRQ I/O

Add bio pcpu caching for normal / IRQ-driven I/O extending REQ_ALLOC_CACHE,
which was limited to iopoll. t/io_uring with an Optane SSD setup showed +7%
for batches of 32 requests and +4.3% for batches of 8.

IRQ, 128/32/32, cache off
IOPS=59.08M, BW=28.84GiB/s, IOS/call=31/31
IOPS=59.30M, BW=28.96GiB/s, IOS/call=32/32
IOPS=59.97M, BW=29.28GiB/s, IOS/call=31/31
IOPS=59.92M, BW=29.26GiB/s, IOS/call=32/32
IOPS=59.81M, BW=29.20GiB/s, IOS/call=32/31

IRQ, 128/32/32, cache on
IOPS=64.05M, BW=31.27GiB/s, IOS/call=32/31
IOPS=64.22M, BW=31.36GiB/s, IOS/call=32/32
IOPS=64.04M, BW=31.27GiB/s, IOS/call=31/31
IOPS=63.16M, BW=30.84GiB/s, IOS/call=32/32

IRQ, 32/8/8, cache off
IOPS=50.60M, BW=24.71GiB/s, IOS/call=7/8
IOPS=50.22M, BW=24.52GiB/s, IOS/call=8/7
IOPS=49.54M, BW=24.19GiB/s, IOS/call=8/8
IOPS=50.07M, BW=24.45GiB/s, IOS/call=7/7
IOPS=50.46M, BW=24.64GiB/s, IOS/call=8/8

IRQ, 32/8/8, cache on
IOPS=51.39M, BW=25.09GiB/s, IOS/call=8/7
IOPS=52.52M, BW=25.64GiB/s, IOS/call=7/8
IOPS=52.57M, BW=25.67GiB/s, IOS/call=8/8
IOPS=52.58M, BW=25.67GiB/s, IOS/call=8/7
IOPS=52.61M, BW=25.69GiB/s, IOS/call=8/8

The next step will be turning it on for other users, hopefully by default.
The only restriction we currently have is that the allocations can't be
done from non-irq context and so needs auditing.

note: needs "bio: safeguard REQ_ALLOC_CACHE bio put" missing in for-6.2/block

v2: fix botched splicing threshold checks
v3: remove merged patch
    limit scope of flags var in bio_put_percpu_cache (Christoph Hellwig)

Pavel Begunkov (3):
  bio: split pcpu cache part of bio_put into a helper
  block/bio: add pcpu caching for non-polling bio_put
  io_uring/rw: enable bio caches for IRQ rw

 block/bio.c   | 93 +++++++++++++++++++++++++++++++++++++++------------
 io_uring/rw.c |  3 +-
 2 files changed, 74 insertions(+), 22 deletions(-)

-- 
2.38.0