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Message-Id: <1446474673-2566-1-git-send-email-paolo.valente@unimore.it>
Date: Mon, 2 Nov 2015 15:31:10 +0100
From: Paolo Valente <paolo.valente@...more.it>
To: Jens Axboe <axboe@...com>,
Matias Bjørling <m@...rling.me>,
Arianna Avanzini <avanzini@...gle.com>
Cc: Paolo Valente <paolo.valente@...more.it>,
Akinobu Mita <akinobu.mita@...il.com>,
"Luis R. Rodriguez" <mcgrof@...e.com>,
Ming Lei <ming.lei@...onical.com>,
Mike Krinkin <krinkin.m.u@...il.com>,
linux-kernel@...r.kernel.org
Subject: [PATCH BUGFIX 0/3] null_blk: fix throughout losses and hangs
Hi,
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 and Arianna
[1] https://lkml.org/lkml/2015/8/19/181
Arianna Avanzini (2):
null_blk: guarantee device restart in all irq modes
null_blk: change type of completion_nsec to unsigned long
Paolo Valente (1):
null_blk: set a separate timer for each command
drivers/block/null_blk.c | 94 +++++++++++++++++-------------------------------
1 file changed, 33 insertions(+), 61 deletions(-)
--
1.9.1
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