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From: Jens Axboe <axboe@kernel.dk>
To: Benny Halevy <bhalevy@scylladb.com>,
	linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-aio@kvack.org
Cc: hch@lst.de, jmoyer@redhat.com, clm@fb.com
Subject: Re: [PATCH 15/26] aio: support for IO polling
Date: Sun, 9 Dec 2018 07:36:24 -0700	[thread overview]
Message-ID: <ad13ccdd-cdc5-adc9-35ca-958a30a9477d@kernel.dk> (raw)
In-Reply-To: <e0494161918d30787fbc759f9d2b77953249ab8b.camel@scylladb.com>

On 12/9/18 3:02 AM, Benny Halevy wrote:
>> +static int __aio_iopoll_check(struct kioctx *ctx, struct io_event __user *event,
>> +			      unsigned int *nr_events, long min_nr, long max_nr)
>> +{
>> +	int ret = 0;
>> +
>> +	while (!*nr_events || !need_resched()) {
> 
> Hmm, it doesn't make sense to spin in this loop
> if the user got _all_ the events he requested, even
> if !need_resched().  How about:
> 
> 	while (!*nr_events || (!need_resched() && *nr_events < max_nr)) {

That checking is done io aio_iopoll_getevents(), there are other
conditions where we don't want to spin, like nr_events >= min_nr for
instance. But all that logic is in aio_iopoll_getevents(), from here we
just know that we probably need to continue if nr_events == 0.

I don't think there's an issue here, and no spinning when we don't need
it.

-- 
Jens Axboe


  reply	other threads:[~2018-12-09 14:36 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-07 22:19 [PATCHSET v6] Support for polled aio (and more) Jens Axboe
2018-12-07 22:19 ` [PATCH 01/26] fs: add an iopoll method to struct file_operations Jens Axboe
2018-12-07 22:19 ` [PATCH 02/26] block: add REQ_HIPRI_ASYNC Jens Axboe
2018-12-07 22:19 ` [PATCH 03/26] block: wire up block device iopoll method Jens Axboe
2018-12-07 22:19 ` [PATCH 04/26] block: use REQ_HIPRI_ASYNC for non-sync polled IO Jens Axboe
2018-12-07 22:19 ` [PATCH 05/26] iomap: wire up the iopoll method Jens Axboe
2018-12-07 22:19 ` [PATCH 06/26] aio: use assigned completion handler Jens Axboe
2018-12-07 22:19 ` [PATCH 07/26] aio: separate out ring reservation from req allocation Jens Axboe
2018-12-07 22:19 ` [PATCH 08/26] aio: don't zero entire aio_kiocb aio_get_req() Jens Axboe
2018-12-07 22:19 ` [PATCH 09/26] aio: only use blk plugs for > 2 depth submissions Jens Axboe
2018-12-07 22:20 ` [PATCH 10/26] aio: use iocb_put() instead of open coding it Jens Axboe
2018-12-07 22:20 ` [PATCH 11/26] aio: split out iocb copy from io_submit_one() Jens Axboe
2018-12-07 22:20 ` [PATCH 12/26] aio: abstract out io_event filler helper Jens Axboe
2018-12-07 22:20 ` [PATCH 13/26] aio: add io_setup2() system call Jens Axboe
2018-12-09 10:12   ` Benny Halevy
2018-12-09 14:37     ` Jens Axboe
2018-12-07 22:20 ` [PATCH 14/26] aio: add support for having user mapped iocbs Jens Axboe
2018-12-07 22:20 ` [PATCH 15/26] aio: support for IO polling Jens Axboe
2018-12-09 10:02   ` Benny Halevy
2018-12-09 14:36     ` Jens Axboe [this message]
2018-12-10  8:10       ` Benny Halevy
2018-12-07 22:20 ` [PATCH 16/26] aio: add submission side request cache Jens Axboe
2018-12-07 22:20 ` [PATCH 17/26] fs: add fget_many() and fput_many() Jens Axboe
2018-12-07 22:20 ` [PATCH 18/26] aio: use fget/fput_many() for file references Jens Axboe
2018-12-07 22:20 ` [PATCH 19/26] aio: split iocb init from allocation Jens Axboe
2018-12-07 22:20 ` [PATCH 20/26] aio: batch aio_kiocb allocation Jens Axboe
2018-12-07 22:20 ` [PATCH 21/26] block: add BIO_HOLD_PAGES flag Jens Axboe
2018-12-07 22:20 ` [PATCH 22/26] block: implement bio helper to add iter bvec pages to bio Jens Axboe
2018-12-07 22:20 ` [PATCH 23/26] fs: add support for mapping an ITER_BVEC for O_DIRECT Jens Axboe
2018-12-07 22:20 ` [PATCH 24/26] aio: add support for pre-mapped user IO buffers Jens Axboe
2018-12-07 22:20 ` [PATCH 25/26] aio: split old ring complete out from aio_complete() Jens Axboe
2018-12-07 22:20 ` [PATCH 26/26] aio: add support for submission/completion rings Jens Axboe
  -- strict thread matches above, loose matches on Subject: below --
2018-12-04 23:37 [PATCHSET v5] Support for polled aio Jens Axboe
2018-12-04 23:37 ` [PATCH 15/26] aio: support for IO polling Jens Axboe
2018-12-05  9:56   ` Benny Halevy
2018-12-05 13:10     ` Jens Axboe
2018-12-06  9:04       ` Benny Halevy

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