From: "jianchao.wang" <jianchao.w.wang@oracle.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: axboe@kernel.dk, viro@zeniv.linux.org.uk,
linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH V2] io_uring: introduce inline reqs for IORING_SETUP_IOPOLL
Date: Tue, 9 Apr 2019 17:46:45 +0800 [thread overview]
Message-ID: <c76b558c-bc12-3247-2bb5-986e5ffcba1f@oracle.com> (raw)
In-Reply-To: <20190409093717.GA15391@infradead.org>
Hi Christoph
On 4/9/19 5:37 PM, Christoph Hellwig wrote:
> On Tue, Apr 09, 2019 at 01:21:54PM +0800, Jianchao Wang wrote:
>> For the IORING_SETUP_IOPOLL case, all of the submission and
>> completion are handled under ctx->uring_lock or in SQ poll thread
>> context, so io_get_req and io_put_req has been serialized well.
>> The only exception is the asynchronous workqueue context where could
>> free the io_kiocb for error. To overcome this, we allocate a new
>> io_kiocb and free the previous inlined one.
>>
>> Based on this, we introduce the preallocated reqs list per ctx and
>> needn't to provide any lock to serialize the updating of list. The
>> performacne benefits from this. The test result of following fio
>> command
>
> I really don't like the idea of exposing this to userspace. Is
> there any good reason to not simply always allocate inline request
> up to a certain ring size?
>
Sorry, I cannot get your point.
There is nothing exposed to userspace. We will try to allocated fixed 128
per-ctx preallocated reqs if IORING_SETUP_IOPOLL. When this inlined reqs
are used up, it will allocated reqs in old fashion.
Thanks
Jianchao
prev parent reply other threads:[~2019-04-09 9:48 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-09 5:21 [PATCH V2] io_uring: introduce inline reqs for IORING_SETUP_IOPOLL Jianchao Wang
2019-04-09 9:37 ` Christoph Hellwig
2019-04-09 9:43 ` Christoph Hellwig
2019-04-09 9:46 ` jianchao.wang [this message]
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