Messages in this thread | | | Subject | Re: [PATCH BUGFIX V2 0/3] null_blk: fix throughput losses and hangs | From | Jens Axboe <> | Date | Tue, 1 Dec 2015 10:52:32 -0700 |
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On 12/01/2015 03:48 AM, Paolo Valente wrote: > Hi, > here is an updated version of the patchset, differing from the > previous version only in that it reinstates the missing extra check > pointed out in [2]. For your convenience, the content of the cover > letter for the previous version follows. > > While doing some tests with the null_blk device driver, we bumped into > two problems: first, unjustified and in some cases high throughput > losses; second, actual hangs. These problems seem to be the > consequence of the combination of three causes, and this patchset > introduces a fix for each of these causes. In particular, changes > address: > . an apparent flaw in the logic with which delayed completions are > implemented: this flaw causes, with unlucky but non-pathological > workloads, actual request-completion delays to become arbitrarily > larger than the configured delay; > . the missing restart of the device queue on the completion of a request in > single-queue non-delayed mode; > . the overflow of the request-delay parameter, when extremely high values > are used (e.g., to spot bugs). > > To avoid possible confusion, we stress that these fixes *do not* have > anything to do with the problems highlighted in [1] (tests of the > multiqueue xen-blkfront and xen-blkback modules with null_blk). > > You can find more details in the patch descriptions.
Thanks Paolo, added.
-- Jens Axboe
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