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From: Avi Kivity <avi@scylladb.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: NeilBrown <neilb@suse.com>, linux-raid@vger.kernel.org
Subject: Re: raid0 vs. mkfs
Date: Mon, 28 Nov 2016 11:11:18 +0200	[thread overview]
Message-ID: <8f633d1b-6250-6f9d-0311-70931d31fe0a@scylladb.com> (raw)
In-Reply-To: <20161128090053.GA9393@infradead.org>

On 11/28/2016 11:00 AM, Christoph Hellwig wrote:
> On Mon, Nov 28, 2016 at 10:58:24AM +0200, Avi Kivity wrote:
>> What I guess is happening is that since the NVMe queue depth is so high, and
>> request the driver receives is sent immediately to the disk and there is
>> nothing to merge it to.  That could indicate the absence of plugging, or
>> just a reluctance to merge TRIMs.
> That is exactly the case, and it's also an issue with online trim.
> I have work in progress block layer trim patches that always plug trims
> and have various TRIM merge improvements including support for ranged
> TRIMs.  It needs a bit more work, but I hope I can post it later
> this week.

Great, good to know.

I still think it should also be fixed in the RAID layer.  There's no 
reason to break a single request in millions of smaller ones, then try 
to merge them into one request back again.  The queuing layer can merge 
when it's given bad patterns from uncontrolled sources, not as an excuse 
to generate bad patterns from within the kernel.

  reply	other threads:[~2016-11-28  9:11 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-11-27 15:24 raid0 vs. mkfs Avi Kivity
2016-11-27 17:09 ` Coly Li
2016-11-27 17:25   ` Avi Kivity
2016-11-27 19:25     ` Doug Dumitru
2016-11-28  4:11 ` Chris Murphy
2016-11-28  7:28   ` Avi Kivity
2016-11-28  7:33     ` Avi Kivity
2016-11-28  5:09 ` NeilBrown
2016-11-28  6:08   ` Shaohua Li
2016-11-28  7:38   ` Avi Kivity
2016-11-28  8:40     ` NeilBrown
2016-11-28  8:58       ` Avi Kivity
2016-11-28  9:00         ` Christoph Hellwig
2016-11-28  9:11           ` Avi Kivity [this message]
2016-11-28  9:15             ` Coly Li
2016-11-28 17:47             ` Shaohua Li
2016-11-29 21:14         ` NeilBrown
2016-11-29 22:45           ` Avi Kivity
2016-12-07  5:08             ` Mike Snitzer
2016-12-07 11:50             ` Coly Li
2016-12-07 12:03               ` Coly Li
2016-12-07 16:59               ` Shaohua Li
2016-12-08 16:44                 ` Coly Li
2016-12-08 19:19                   ` Shaohua Li
2016-12-09  7:34                     ` Coly Li
2016-12-12  3:17                       ` NeilBrown
2017-06-29 15:15                   ` Avi Kivity
2017-06-29 15:31                     ` Coly Li
2017-06-29 15:36                       ` Avi Kivity
2017-01-22 18:01 ` Avi Kivity
2017-01-23 12:26   ` Coly Li

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