Re: [PATCH 0/4] block: account io: kill atomic operations

From	Ming Lei <tom.leiming@gmail.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 0/4] block: account io: kill atomic operations
Date	2015-07-16 17:10 +0200
Message-ID	<pMSXn-1Ro-7@gated-at.bofh.it> (permalink)
References	<pMHSh-2E1-1@gated-at.bofh.it> <pMSE2-1eX-17@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Thu, Jul 16, 2015 at 10:48 PM, Jens Axboe <axboe@kernel.dk> wrote:
> On 07/15/2015 09:16 PM, Ming Lei wrote:
>>
>> Hi,
>>
>> This patches kills two kinds of atomic operations in block
>> accounting I/O.
>>
>> The 1st two patches convert atomic refcount of partition
>> into percpu refcount.
>>
>> The 2nd two patches converts partition->in_flight[] into percpu
>> variable.
>>
>> With this change, ~15% throughput improvement can be observed
>> when running fio(randread) over null blk in a dual-socket
>> environment.
>
>
> I've played with this before, but always ran into the hurdle of making
> part_in_flight() too expensive ended up hurting results in the end. Making

Yes, it is a bit expensive, but it is only run at most one time per tick for
one partition.

> the inc/dec parts of accounting percpu is a no-brainer, unfortunately the
> summing then becomes pretty expensive. I'll run this through some testing
> and see what kind of results I get.

The first two patches should be fine, and it still can get ~8% improvement
in my test.

>
> --
> Jens Axboe
>



-- 
Ming Lei
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[PATCH 0/4] block: account io: kill atomic operations Ming Lei <tom.leiming@gmail.com> - 2015-07-16 05:20 +0200
  [PATCH 3/4] block: partition: introduce 'cpu' para to part_inc|dec_in_flight Ming Lei <tom.leiming@gmail.com> - 2015-07-16 05:30 +0200
  [PATCH 1/4] block: partition: introduce hd_free_part() Ming Lei <tom.leiming@gmail.com> - 2015-07-16 05:30 +0200
  [PATCH 2/4] block: partition: convert percpu ref Ming Lei <tom.leiming@gmail.com> - 2015-07-16 05:30 +0200
    Re: [PATCH 2/4] block: partition: convert percpu ref Tejun Heo <tj@kernel.org> - 2015-07-16 16:40 +0200
  [PATCH 4/4] block: account io: convert part->in_fligh[] into percpu variable Ming Lei <tom.leiming@gmail.com> - 2015-07-16 05:30 +0200
    Re: [PATCH 4/4] block: account io: convert part->in_fligh[] into  percpu variable Tejun Heo <tj@kernel.org> - 2015-07-16 16:50 +0200
  Re: [PATCH 0/4] block: account io: kill atomic operations Jens Axboe <axboe@kernel.dk> - 2015-07-16 16:50 +0200
    Re: [PATCH 0/4] block: account io: kill atomic operations Tejun Heo <tj@kernel.org> - 2015-07-16 17:00 +0200
      Re: [PATCH 0/4] block: account io: kill atomic operations Jens Axboe <axboe@kernel.dk> - 2015-07-16 17:10 +0200
    Re: [PATCH 0/4] block: account io: kill atomic operations Jens Axboe <axboe@kernel.dk> - 2015-07-16 17:10 +0200
    Re: [PATCH 0/4] block: account io: kill atomic operations Ming Lei <tom.leiming@gmail.com> - 2015-07-16 17:10 +0200

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