From: Pavel Begunkov <[email protected]>
To: Jens Axboe <[email protected]>,
[email protected], [email protected]
Subject: Re: [PATCH 2/2] io_uring: batch getting pcpu references
Date: Wed, 18 Dec 2019 12:25:15 +0300 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
On 12/18/2019 2:31 AM, Jens Axboe wrote:
> On 12/17/19 4:21 PM, Jens Axboe wrote:
>> On 12/17/19 3:28 PM, Pavel Begunkov wrote:
>>> percpu_ref_tryget() has its own overhead. Instead getting a reference
>>> for each request, grab a bunch once per io_submit_sqes().
>>>
>>> basic benchmark with submit and wait 128 non-linked nops showed ~5%
>>> performance gain. (7044 KIOPS vs 7423)
>>>
>>> Signed-off-by: Pavel Begunkov <[email protected]>
>>> ---
>>>
>>> For notice: it could be done without @extra_refs variable,
>>> but looked too tangled because of gotos.
>>>
>>>
>>> fs/io_uring.c | 11 ++++++++---
>>> 1 file changed, 8 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>>> index cf4138f0e504..6c85dfc62224 100644
>>> --- a/fs/io_uring.c
>>> +++ b/fs/io_uring.c
>>> @@ -845,9 +845,6 @@ static struct io_kiocb *io_get_req(struct io_ring_ctx *ctx,
>>> gfp_t gfp = GFP_KERNEL | __GFP_NOWARN;
>>> struct io_kiocb *req;
>>>
>>> - if (!percpu_ref_tryget(&ctx->refs))
>>> - return NULL;
>>> -
>>> if (!state) {
>>> req = kmem_cache_alloc(req_cachep, gfp);
>>> if (unlikely(!req))
>>> @@ -3929,6 +3926,7 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr,
>>> struct io_submit_state state, *statep = NULL;
>>> struct io_kiocb *link = NULL;
>>> int i, submitted = 0;
>>> + unsigned int extra_refs;
>>> bool mm_fault = false;
>>>
>>> /* if we have a backlog and couldn't flush it all, return BUSY */
>>> @@ -3941,6 +3939,10 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr,
>>> statep = &state;
>>> }
>>>
>>> + if (!percpu_ref_tryget_many(&ctx->refs, nr))
>>> + return -EAGAIN;
>>> + extra_refs = nr;
>>> +
>>> for (i = 0; i < nr; i++) {
>>> struct io_kiocb *req = io_get_req(ctx, statep);
>>>
>
> This also needs to come before the submit_state_start().
>
Good catch, forgot to handle this. Thanks
> I forgot to mention that I really like the idea, no point in NOT batching
> the refs when we know exactly how many refs we need.
>
--
Pavel Begunkov
next prev parent reply other threads:[~2019-12-18 9:25 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-17 22:28 [PATCH 0/2] optimise ctx's refs grabbing in io_uring Pavel Begunkov
2019-12-17 22:28 ` [PATCH 1/2] pcpu_ref: add percpu_ref_tryget_many() Pavel Begunkov
2019-12-17 23:42 ` Jens Axboe
2019-12-18 16:26 ` Tejun Heo
2019-12-18 17:49 ` Dennis Zhou
2019-12-21 15:36 ` Pavel Begunkov
2019-12-17 22:28 ` [PATCH 2/2] io_uring: batch getting pcpu references Pavel Begunkov
2019-12-17 23:21 ` Jens Axboe
2019-12-17 23:31 ` Jens Axboe
2019-12-18 9:25 ` Pavel Begunkov [this message]
2019-12-18 9:23 ` Pavel Begunkov
2019-12-18 0:02 ` Jens Axboe
2019-12-18 10:41 ` Pavel Begunkov
2019-12-21 16:15 ` [PATCH v2 0/3] optimise ctx's refs grabbing in io_uring Pavel Begunkov
2019-12-21 16:15 ` [PATCH v2 1/3] pcpu_ref: add percpu_ref_tryget_many() Pavel Begunkov
2019-12-21 16:15 ` [PATCH v2 2/3] io_uring: batch getting pcpu references Pavel Begunkov
2019-12-21 16:15 ` [PATCH RFC v2 3/3] io_uring: batch get(ctx->ref) across submits Pavel Begunkov
2019-12-21 16:20 ` Pavel Begunkov
2019-12-21 16:38 ` Jens Axboe
2019-12-21 16:48 ` Pavel Begunkov
2019-12-21 17:01 ` Jens Axboe
2019-12-21 17:26 ` Pavel Begunkov
2019-12-21 20:12 ` [PATCH v3 0/2] optimise ctx's refs grabbing in io_uring Pavel Begunkov
2019-12-21 20:12 ` [PATCH v3 1/2] pcpu_ref: add percpu_ref_tryget_many() Pavel Begunkov
2019-12-21 20:12 ` [PATCH v3 2/2] io_uring: batch getting pcpu references Pavel Begunkov
2019-12-21 21:56 ` Pavel Begunkov
2019-12-28 11:13 ` [PATCH v4 0/2] optimise ctx's refs grabbing in io_uring Pavel Begunkov
2019-12-28 11:13 ` [PATCH v4 1/2] pcpu_ref: add percpu_ref_tryget_many() Pavel Begunkov
2019-12-28 11:13 ` [PATCH v4 2/2] io_uring: batch getting pcpu references Pavel Begunkov
2019-12-28 11:15 ` Pavel Begunkov
2019-12-28 17:03 ` Jens Axboe
2019-12-28 18:37 ` Pavel Begunkov
2019-12-30 3:33 ` Brian Gianforcaro
2019-12-30 18:45 ` Pavel Begunkov
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