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Groups > linux.kernel > #1183993
| From | Jens Axboe <axboe@fb.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH 3/3] block: by default, limit maximum discard size to 64MB |
| Date | 2015-07-14 22:50 +0200 |
| Message-ID | <pMfjk-2VX-23@gated-at.bofh.it> (permalink) |
| References | <pMdrb-bw-3@gated-at.bofh.it> <pMdAT-n6-33@gated-at.bofh.it> <pMfjj-2VX-15@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On 07/14/2015 02:44 PM, Mike Snitzer wrote: > 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. I'd argue that's most of them... But the testing we did was on NVMe. I can limit it to NVMe, no big deal. > If this goes in I know for sure I'll need to work around it in DM-thinp. In any case, that's a good point, dm/md should not have their own lower restrictions. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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Re: [PATCH 3/3] block: by default, limit maximum discard size to 64MB Mike Snitzer <snitzer@redhat.com> - 2015-07-14 22:50 +0200
Re: [PATCH 3/3] block: by default, limit maximum discard size to 64MB Jens Axboe <axboe@fb.com> - 2015-07-14 22:50 +0200
Re: [PATCH 3/3] block: by default, limit maximum discard size to 64MB Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-07-15 13:50 +0200
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