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From: Avi Kivity <avi@scylladb.com>
To: Christoph Hellwig <hch@lst.de>
Cc: linux-xfs@vger.kernel.org, michaelcallahan@fb.com
Subject: Re: discard improvements
Date: Sat, 5 Nov 2016 20:18:05 +0200	[thread overview]
Message-ID: <5a50a07c-369d-1a41-2111-f9ee91ac7425@scylladb.com> (raw)
In-Reply-To: <20161031151412.GA14804@lst.de>

On 10/31/2016 05:14 PM, Christoph Hellwig wrote:
> On Fri, Oct 28, 2016 at 01:11:55PM +0300, Avi Kivity wrote:
>> With these patches, is it reasonable to run with discard enabled, or is
>> more work needed?
> As usual the answer is: it depends.  With the high-end NVMe devices
> I've been testing with you absolutely should enable discard.  With
> SAS SSDs the same is probably true.  I haven't done much testing with
> SATA SSDs but I'd be more cautious there, especially as very few seem
> to support queued TRIM yet.

Thanks.

The big problem with "it depends" is that usually the information it 
depends on is not available, so the application has to rely on a human 
to guess correctly.  With the trend for machines to be managed by 
machines, it's really hard to get optimal performance.  So exposure of 
any information that can help to make a decision, including that the 
kernel can make good use of TRIM, will be very helpful.

  reply	other threads:[~2016-11-05 18:18 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-10-17 20:22 Christoph Hellwig
2016-10-17 20:22 ` [PATCH 1/3] xfs: fix the AG loop in xfs_alloc_vextent for busy extents Christoph Hellwig
2016-10-19 13:48   ` Brian Foster
2016-10-21 12:48     ` Christoph Hellwig
2016-10-21 14:41       ` Brian Foster
2016-11-08  6:15   ` Dave Chinner
2016-11-10 19:17     ` Christoph Hellwig
2016-10-17 20:22 ` [PATCH 2/3] xfs: don't block the log commit handler for discards Christoph Hellwig
2016-10-17 23:29   ` Dave Chinner
2016-10-18  5:05     ` Christoph Hellwig
2016-10-19 10:58     ` Christoph Hellwig
2016-10-28 16:16       ` Michael Callahan
2016-10-31 15:16         ` Christoph Hellwig
2016-10-17 20:22 ` [PATCH 3/3] xfs: merge discard requests Christoph Hellwig
2016-10-28 10:11 ` discard improvements Avi Kivity
2016-10-31 15:14   ` Christoph Hellwig
2016-11-05 18:18     ` Avi Kivity [this message]
2016-11-06 16:36       ` Christoph Hellwig
2016-11-06 23:21         ` Dave Chinner

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