From: Mike Snitzer <snitzer@redhat.com>
To: Jens Axboe <axboe@fb.com>
Cc: linux-kernel@vger.kernel.org, hch@lst.de
Subject: Re: [PATCH 3/3] block: by default, limit maximum discard size to 64MB
Date: Tue, 14 Jul 2015 16:44:20 -0400 [thread overview]
Message-ID: <20150714204419.GA7915@redhat.com> (raw)
In-Reply-To: <1436899703-31966-4-git-send-email-axboe@fb.com>
On Tue, Jul 14 2015 at 2:48pm -0400,
Jens Axboe <axboe@fb.com> wrote:
> Lots of devices exhibit very high latencies for big discards, hurting
> reads and writes. By default, limit the max discard we will build to
> 64MB. This value has shown good results across a number of devices.
>
> This will potentially hurt discard throughput, from a provisioning
> point of view (when the user does mkfs.xfs, for instance, and mkfs
> issues a full device discard). If that becomes an issue, we could
> have different behavior for provisioning vs runtime discards.
>
> Signed-off-by: Jens Axboe <axboe@fb.com>
Christoph suggested you impose this default for the specific
drivers/devices that benefit. I'm not following why imposing a 64MB
default is the right thing to do for all devices.
If this goes in I know for sure I'll need to work around it in DM-thinp.
next prev parent reply other threads:[~2015-07-14 20:44 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-14 18:48 [PATCH 0/3 v2] Configurable max discard size Jens Axboe
2015-07-14 18:48 ` [PATCH 1/3] block: have drivers use blk_queue_max_discard_sectors() Jens Axboe
2015-07-16 14:46 ` Jeff Moyer
2015-07-14 18:48 ` [PATCH 2/3] block: make /sys/block/<dev>/queue/discard_max_bytes writeable Jens Axboe
2015-07-16 15:07 ` Jeff Moyer
2015-07-16 15:11 ` Jens Axboe
2015-07-14 18:48 ` [PATCH 3/3] block: by default, limit maximum discard size to 64MB Jens Axboe
2015-07-14 20:44 ` Mike Snitzer [this message]
2015-07-14 20:45 ` Jens Axboe
2015-07-14 21:48 ` Jens Axboe
2015-07-15 11:46 ` Austin S Hemmelgarn
2015-07-15 15:30 ` Jens Axboe
2015-07-15 16:29 ` Mike Snitzer
2015-07-15 22:14 ` Jens Axboe
2015-08-05 13:34 ` Mike Snitzer
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