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Bug #9751
closedAllocation throttling misplacing ditto blocks
Start date:
2018-08-16
Due date:
% Done:
100%
Estimated time:
Difficulty:
Medium
Tags:
needs-triage
Gerrit CR:
Description
During synthetic random write benchmarks I found many secondary and tertiary block copies allocations form the same vdevs (more then 10% of all allocations!):
1 4618459 2 667430 3 420 1 4605120 2 672441 3 346 1 4635516 2 663064 3 760
That at the end caused some allocation issues I addressed in #9738. Digging toward the source I found that the poor allocation is caused by allocation throttling. I suppose periodically under the heavy load one or another random disk becomes the only one with allocations available, and starts collecting all ditto blocks. Simple patch I made to relax allocation of secondary and tertiary blocks radically fixed the allocation issue, and seems even increased performance a bit:
1 6222858 1 6135604 1 6062702
Updated by Alexander Motin almost 4 years ago
Updated by Electric Monk almost 3 years ago
- Status changed from In Progress to Closed
- % Done changed from 0 to 100
git commit dbcaafbddbc82f9a7b3310551c4bcdb862b2515a
commit dbcaafbddbc82f9a7b3310551c4bcdb862b2515a Author: Alexander Motin <mav@FreeBSD.org> Date: 2019-05-30T16:46:52.000Z 9751 Allocation throttling misplacing ditto blocks Portions contributed by: Kody Kantor <kody.kantor@joyent.com> Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com> Reviewed by: Matt Ahrens <matt@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Approved by: Gordon Ross <gwr@nexenta.com>
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