Messages in this thread | | | Date | Tue, 14 Jul 2015 16:44:20 -0400 | From | Mike Snitzer <> | Subject | Re: [PATCH 3/3] block: by default, limit maximum discard size to 64MB |
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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.
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