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: Fri, 1 Apr 2016 08:34:42 -0600 [thread overview]
Message-ID: <56FE8702.6030306@fb.com> (raw)
In-Reply-To: <20160401062745.GY11812@dastard>
On 04/01/2016 12:27 AM, Dave Chinner wrote:
> On Thu, Mar 31, 2016 at 09:25:33PM -0600, Jens Axboe wrote:
>> On 03/31/2016 06:46 PM, Dave Chinner wrote:
>>>>> virtio in guest, XFS direct IO -> no-op -> scsi in host.
>>>>
>>>> That has write back caching enabled on the guest, correct?
>>>
>>> No. It uses virtio,cache=none (that's the "XFS Direct IO" bit above).
>>> Sorry for not being clear about that.
>>
>> That's fine, it's one less worry if that's not the case. So if you
>> cat the 'write_cache' file in the virtioblk sysfs block queue/
>> directory, it says 'write through'? Just want to confirm that we got
>> that propagated correctly.
>
> No such file. But I did find:
>
> $ cat /sys/block/vdc/cache_type
> write back
>
> Which is what I'd expect it to safe given the man page description
> of cache=none:
>
> Note that this is considered a writeback mode and the guest
> OS must handle the disk write cache correctly in order to
> avoid data corruption on host crashes.
>
> To make it say "write through" I need to use cache=directsync, but
> I have no need for such integrity guarantees on a volatile test
> device...
I wasn't as concerned about the integrity side, more if it's flagged as
write back then we induce further throttling. But I'll see if I can get
your test case reproduced, then I don't see why it can't get fixed. I'm
off all of next week though, so probably won't be until the week after...
--
Jens Axboe
next prev parent reply other threads:[~2016-04-01 14:34 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
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 [this message]
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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