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From: Christoph Hellwig <hch@infradead.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-fsdevel@vger.kernel.org, linux-aio@kvack.org,
	linux-block@vger.kernel.org, hch@lst.de, viro@zeniv.linux.org.uk
Subject: Re: [PATCH 19/22] aio: support kernel side submission for aio with SCQRING
Date: Thu, 27 Dec 2018 14:57:53 +0100	[thread overview]
Message-ID: <20181227135753.GE25525@infradead.org> (raw)
In-Reply-To: <20181221192236.12866-20-axboe@kernel.dk>

On Fri, Dec 21, 2018 at 12:22:33PM -0700, Jens Axboe wrote:
> If an application sets IOCTX_FLAG_SCQTHREAD, the io_context gets a
> single thread backing. If used with buffered IO, this will limit
> the device queue depth to 1, but it will be async, IOs will simply
> be serialized.
> 
> Or an application can set IOCTX_FLAG_SQWQ, in which case the io_context
> gets a work queue backing. The concurrency level is the mininum of
> twice the available CPUs, or the queue depth specific for the context.
> For this mode, we attempt to do buffered reads inline, in case they are
> cached. So we should only punt to a workqueue, if we would have to block
> to get our data.

I'm really worried about having this code present twice.  Do we have
strong use cases for both?  Can't we emulate IOCTX_FLAG_SCQTHREAD good
enough with a workqueue without concurrency management?

  reply	other threads:[~2018-12-27 13:57 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-21 19:22 [PATCHSET v10] Support for polled and buffered aio (and more) Jens Axboe
2018-12-21 19:22 ` [PATCH 01/22] fs: add an iopoll method to struct file_operations Jens Axboe
2018-12-21 19:22 ` [PATCH 02/22] block: add bio_set_polled() helper Jens Axboe
2018-12-21 19:22 ` [PATCH 03/22] block: wire up block device iopoll method Jens Axboe
2018-12-21 19:22 ` [PATCH 04/22] block: use REQ_HIPRI_ASYNC for non-sync polled IO Jens Axboe
2018-12-21 19:25   ` Jens Axboe
2018-12-27 13:15     ` Christoph Hellwig
2018-12-27 20:22       ` Jens Axboe
2018-12-21 19:22 ` [PATCH 05/22] block: use bio_set_polled() helper for O_DIRECT Jens Axboe
2018-12-21 19:22 ` [PATCH 06/22] iomap: wire up the iopoll method Jens Axboe
2018-12-21 19:22 ` [PATCH 07/22] aio: add io_setup2() system call Jens Axboe
2018-12-27 13:55   ` Christoph Hellwig
2018-12-27 20:27     ` Jens Axboe
2018-12-21 19:22 ` [PATCH 08/22] aio: support for IO polling Jens Axboe
2018-12-27 13:55   ` Christoph Hellwig
2018-12-27 20:29     ` Jens Axboe
2018-12-21 19:22 ` [PATCH 09/22] aio: add submission side request cache Jens Axboe
2018-12-27 13:56   ` Christoph Hellwig
2018-12-27 20:31     ` Jens Axboe
2018-12-21 19:22 ` [PATCH 10/22] fs: add fget_many() and fput_many() Jens Axboe
2018-12-21 19:22 ` [PATCH 11/22] aio: use fget/fput_many() for file references Jens Axboe
2018-12-21 19:22 ` [PATCH 12/22] aio: split iocb init from allocation Jens Axboe
2018-12-21 19:22 ` [PATCH 13/22] aio: batch aio_kiocb allocation Jens Axboe
2018-12-21 19:22 ` [PATCH 14/22] aio: split old ring complete out from aio_complete() Jens Axboe
2018-12-21 19:22 ` [PATCH 15/22] aio: pass in user index to __io_submit_one() Jens Axboe
2018-12-21 19:22 ` [PATCH 16/22] aio: add support for submission/completion rings Jens Axboe
2018-12-27 13:47   ` Christoph Hellwig
2019-01-02 16:28     ` Jens Axboe
2019-01-02 20:32       ` Jens Axboe
2019-01-02 19:11   ` Jeff Moyer
2018-12-21 19:22 ` [PATCH 17/22] block: implement bio helper to add iter bvec pages to bio Jens Axboe
2018-12-21 19:22 ` [PATCH 18/22] aio: add support for pre-mapped user IO buffers Jens Axboe
2018-12-27 13:57   ` Christoph Hellwig
2018-12-21 19:22 ` [PATCH 19/22] aio: support kernel side submission for aio with SCQRING Jens Axboe
2018-12-27 13:57   ` Christoph Hellwig [this message]
2018-12-27 20:34     ` Jens Axboe
2018-12-21 19:22 ` [PATCH 20/22] aio: enable polling for IOCTX_FLAG_SQTHREAD Jens Axboe
2018-12-21 19:22 ` [PATCH 21/22] aio: utilize io_event->res2 for CQ ring Jens Axboe
2018-12-21 19:22 ` [PATCH 22/22] aio: add my copyright Jens Axboe

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