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: [PATCHSET v3][RFC] Make background writeback not suck
Date: Thu, 31 Mar 2016 21:39:25 -0600 [thread overview]
Message-ID: <56FDED6D.4070200@fb.com> (raw)
In-Reply-To: <56FDEB1A.2030404@fb.com>
On 03/31/2016 09:29 PM, Jens Axboe wrote:
>>> I can't seem to reproduce this at all. On an nvme device, I get a
>>> fairly steady 60K/sec file creation rate, and we're nowhere near
>>> being IO bound. So the throttling has no effect at all.
>>
>> That's too slow to show the stalls - your likely concurrency bound
>> in allocation by the default AG count (4) from mkfs. Use mkfs.xfs -d
>> agcount=32 so that every thread works in it's own AG.
>
> That's the key, with that I get 300-400K ops/sec instead. I'll run some
> testing with this tomorrow and see what I can find, it did one full run
> now and I didn't see any issues, but I need to run it at various
> settings and see if I can find the issue.
No stalls seen, I get the same performance with it disabled and with it
enabled, at both default settings, and lower ones (wb_percent=20).
Looking at iostat, we don't drive a lot of depth, so it makes sense,
even with the throttling we're doing essentially the same amount of IO.
What does 'nr_requests' say for your virtio_blk device? Looks like
virtio_blk has a queue_depth setting, but it's not set by default, and
then it uses the free entries in the ring. But I don't know what that is...
--
Jens Axboe
next prev parent reply other threads:[~2016-04-01 3:39 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-30 15:07 [PATCHSET v3][RFC] Make background writeback not suck Jens Axboe
2016-03-30 15:07 ` [PATCH 1/9] writeback: propagate the various reasons for writeback Jens Axboe
2016-03-30 15:07 ` [PATCH 2/9] writeback: add wbc_to_write() Jens Axboe
2016-03-30 15:07 ` [PATCH 3/9] writeback: use WRITE_SYNC for reclaim or sync writeback Jens Axboe
2016-03-30 15:07 ` [PATCH 4/9] writeback: track if we're sleeping on progress in balance_dirty_pages() Jens Axboe
2016-04-13 13:08 ` Jan Kara
2016-04-13 14:20 ` Jens Axboe
2016-03-30 15:07 ` [PATCH 5/9] block: add ability to flag write back caching on a device Jens Axboe
2016-03-30 15:42 ` Christoph Hellwig
2016-03-30 15:46 ` Jens Axboe
2016-03-30 16:23 ` Jens Axboe
2016-03-30 17:29 ` Christoph Hellwig
2016-03-30 15:07 ` [PATCH 6/9] sd: inform block layer of write cache state Jens Axboe
2016-03-30 15:07 ` [PATCH 7/9] NVMe: " Jens Axboe
2016-03-30 15:07 ` [PATCH 8/9] block: add code to track actual device queue depth Jens Axboe
2016-03-30 15:07 ` [PATCH 9/9] writeback: throttle buffered writeback Jens Axboe
2016-03-31 8:24 ` [PATCHSET v3][RFC] Make background writeback not suck Dave Chinner
2016-03-31 14:29 ` Jens Axboe
2016-03-31 16:21 ` Jens Axboe
2016-04-01 0:56 ` Dave Chinner
2016-04-01 3:29 ` Jens Axboe
2016-04-01 3:33 ` Jens Axboe
2016-04-01 3:39 ` Jens Axboe [this message]
2016-04-01 6:16 ` Dave Chinner
2016-04-01 14:33 ` Jens Axboe
2016-04-01 5:04 ` Dave Chinner
2016-04-01 0:46 ` Dave Chinner
2016-04-01 3:25 ` Jens Axboe
2016-04-01 6:27 ` Dave Chinner
2016-04-01 14:34 ` Jens Axboe
2016-03-31 22:09 ` Holger Hoffstätte
2016-04-01 1:01 ` Dave Chinner
2016-04-01 1:01 ` Dave Chinner
2016-04-01 16:58 ` Holger Hoffstätte
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