From: Pavel Begunkov <email@example.com>
To: Hao Xu <firstname.lastname@example.org>, Jens Axboe <email@example.com>
Cc: firstname.lastname@example.org, Joseph Qi <email@example.com>
Subject: Re: [PATCH] io_uring: don't free request to slab
Date: Wed, 25 Aug 2021 17:02:03 +0100 [thread overview]
Message-ID: <firstname.lastname@example.org> (raw)
On 8/25/21 4:38 PM, Hao Xu wrote:
> 在 2021/8/25 下午9:28, Pavel Begunkov 写道:
>> On 8/25/21 12:40 PM, Hao Xu wrote:
>>> It's not neccessary to free the request back to slab when we fail to
>>> get sqe, just update state->free_reqs pointer.
>> It's a bit hackish because depends on the request being drawn
>> from the array in a particular way. How about returning it
> It seems a req is always allocated from state->reqs, so it should be
> ok? I actually didn't understand 'hackish' here, do you mean
> io_submit_sqes() shouldn't move state->free_reqs which is req caches'
> internal implementation?
I mean it uses implicit knowledge of how io_alloc_req() works, which
may and actually will change. It's just always too easy to forget
about that little one-off thing while changing another chunk.
To give an example, if one decides to remake it and first serve
requests from state->free_list and only when it's empty look into
state->reqs, it's too easy to forget opening a pretty severe
If there is not much profit from it comparing to the risks, I'd
personally prefer to go with a safer way.
>> into state->free_list. That thing is as cold as it can get,
>> only buggy apps can hit it.
prev parent reply other threads:[~2021-08-25 16:03 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-25 11:40 [PATCH] io_uring: don't free request to slab Hao Xu
2021-08-25 13:28 ` Pavel Begunkov
2021-08-25 15:38 ` Hao Xu
2021-08-25 16:02 ` Pavel Begunkov [this message]
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