From: Jens Axboe <axboe@fb.com>
To: Dave Chinner <david@fromorbit.com>
Cc: <linux-kernel@vger.kernel.org>, <linux-fsdevel@vger.kernel.org>,
<linux-block@vger.kernel.org>
Subject: Re: [PATCH 2/6] writeback: wb_start_writeback() should use WB_SYNC_ALL for WB_REASON_SYNC
Date: Tue, 22 Mar 2016 15:40:28 -0600 [thread overview]
Message-ID: <56F1BBCC.8050004@fb.com> (raw)
In-Reply-To: <20160322213427.GR11812@dastard>
On 03/22/2016 03:34 PM, Dave Chinner wrote:
> On Tue, Mar 22, 2016 at 11:55:16AM -0600, Jens Axboe wrote:
>> If you call sync, the initial call to wakeup_flusher_threads() ends up
>> calling wb_start_writeback() with reason=WB_REASON_SYNC, but
>> wb_start_writeback() always uses WB_SYNC_NONE as the writeback mode.
>> Ensure that we use WB_SYNC_ALL for a sync operation.
>
> This seems wrong to me. We want background write to happen as
> quickly as possible and /not block/ when we first kick sync.
It's not going to block. wakeup_flusher_threads() async queues writeback
work through wb_start_writeback().
> The latter blocking passes of sync use WB_SYNC_ALL to ensure that we
> block waiting for all remaining IO to be issued and waited on, but
> the background writeback doesn't need to do this.
That's fine, they can get to wait on the previously issued IO, which was
properly submitted with WB_SYNC_ALL.
Maybe I'm missing your point?
--
Jens Axboe
next prev parent reply other threads:[~2016-03-22 21:40 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-22 17:55 [PATCHSET][RFC] Make background writeback not suck Jens Axboe
2016-03-22 17:55 ` [PATCH 1/6] block: ensure we don't truncate top bits of the request command flags Jens Axboe
2016-03-22 18:59 ` Christoph Hellwig
2016-03-22 19:01 ` Jens Axboe
2016-03-25 2:08 ` Mike Christie
2016-03-25 4:18 ` Jens Axboe
2016-03-22 17:55 ` [PATCH 2/6] writeback: wb_start_writeback() should use WB_SYNC_ALL for WB_REASON_SYNC Jens Axboe
2016-03-22 21:34 ` Dave Chinner
2016-03-22 21:40 ` Jens Axboe [this message]
2016-03-22 21:51 ` Jens Axboe
2016-03-22 22:04 ` Dave Chinner
2016-03-22 22:07 ` Jens Axboe
2016-03-22 17:55 ` [PATCH 3/6] block: add ability to flag write back caching on a device Jens Axboe
2016-03-22 18:57 ` Christoph Hellwig
2016-03-22 18:59 ` Jens Axboe
2016-03-22 17:55 ` [PATCH 4/6] sd: inform block layer of write cache state Jens Axboe
2016-03-22 17:55 ` [PATCH 5/6] NVMe: " Jens Axboe
2016-03-22 17:55 ` [PATCH 6/6] writeback: throttle buffered writeback Jens Axboe
2016-03-22 20:12 ` Jeff Moyer
2016-03-22 20:19 ` Jens Axboe
2016-03-22 20:27 ` Jeff Moyer
2016-03-22 21:30 ` Shaohua Li
2016-03-22 21:35 ` Jens Axboe
2016-03-22 21:51 ` [PATCHSET][RFC] Make background writeback not suck Dave Chinner
2016-03-22 22:03 ` Jens Axboe
2016-03-22 22:31 ` Dave Chinner
2016-03-22 22:57 ` Jens Axboe
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