From: Pavel Begunkov <asml.silence@gmail.com>
To: Tejun Heo <tj@kernel.org>, axboe@kernel.dk
Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-team@fb.com, cgroups@vger.kernel.org, newella@fb.com,
josef@toxicpanda.com, ming.lei@redhat.com, bvanassche@acm.org
Subject: Re: [PATCHSET v2 block/for-5.8] iocost: improve use_delay and latency target handling
Date: Mon, 13 Apr 2020 19:56:26 +0300 [thread overview]
Message-ID: <dd55f890-740c-16b5-77bd-4c6fdb710b3d@gmail.com> (raw)
In-Reply-To: <20200413162758.97252-1-tj@kernel.org>
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On 13/04/2020 19:27, Tejun Heo wrote:
> Changes from v1[1]
>
> * Dropped 0002-block-add-request-io_data_len.patch and updated to use
> rq->stats_sectors instead as suggested by Pavel Begunkov.
rq->stats_sectors is set only when there is QUEUE_FLAG_STATS, see
blk_mq_start_request(). I don't see blk-iocost requiring it. Did I miss something?
>
> This patchset improves the following two iocost control behaviors.
>
> * iocost was failing to punish heavy shared IO generators (file metadata, memory
> reclaim) through use_delay mechanism - use_delay automatically decays which
> works well for iolatency but doesn't match how iocost behaves. This led to
> e.g. memory bombs which generate a lot of swap IOs to use over their allotted
> amount. This is fixed by adding non-decaying use_delay mechanism.
>
> * The same latency targets were being applied regardless of the IO sizes. While
> this works fine for loose targets, it gets in the way when trying to tigthen
> them - a latency target adequate for a 4k IO is too short for a 1 meg IO.
> iocost now discounts the size portion of cost when testing whether a given IO
> met or missed its latency target.
>
> While at it, it also makes minor changse to iocost_monitor.py.
>
> This patchset contains the following five patches.
>
> 0001-blk-iocost-switch-to-fixed-non-auto-decaying-use_del.patch
> 0002-blk-iocost-account-for-IO-size-when-testing-latencie.patch
> 0003-iocost_monitor-exit-successfully-if-interval-is-zero.patch
> 0004-iocost_monitor-drop-string-wrap-around-numbers-when-.patch
>
> and is also available in the following git branch.
>
> git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git iocost-delay-latency-v2
>
> diffstat follows. Thanks.
>
> block/Kconfig | 1
> block/blk-cgroup.c | 6 ++++
> block/blk-iocost.c | 56 +++++++++++++++++++++++++++++------------
> include/linux/blk-cgroup.h | 43 ++++++++++++++++++++++++-------
> tools/cgroup/iocost_monitor.py | 48 +++++++++++++++++++----------------
> 5 files changed, 106 insertions(+), 48 deletions(-)
>
> --
> tejun
>
> [1] http://lkml.kernel.org/r/20200408201450.3959560-1-tj@kernel.org
>
--
Pavel Begunkov
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next prev parent reply other threads:[~2020-04-13 16:57 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-13 16:27 [PATCHSET v2 block/for-5.8] iocost: improve use_delay and latency target handling Tejun Heo
2020-04-13 16:27 ` [PATCH 1/4] blk-iocost: switch to fixed non-auto-decaying use_delay Tejun Heo
2020-04-13 16:27 ` [PATCH 2/4] blk-iocost: account for IO size when testing latencies Tejun Heo
2020-04-13 16:27 ` [PATCH 3/4] iocost_monitor: exit successfully if interval is zero Tejun Heo
2020-04-13 16:27 ` [PATCH 4/4] iocost_monitor: drop string wrap around numbers when outputting json Tejun Heo
2020-04-13 16:56 ` Pavel Begunkov [this message]
2020-04-13 17:00 ` [PATCHSET v2 block/for-5.8] iocost: improve use_delay and latency target handling Pavel Begunkov
2020-04-13 17:08 ` Tejun Heo
2020-04-13 18:49 ` Pavel Begunkov
2020-04-30 21:55 ` Jens Axboe
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