From mboxrd@z Thu Jan 1 00:00:00 1970 From: snitzer@redhat.com (Mike Snitzer) Date: Tue, 13 Nov 2018 20:28:10 -0500 Subject: nvme: utilize two queue maps, one for reads and one for writes In-Reply-To: References: <20181114004148.GA29545@roeck-us.net> Message-ID: <20181114012810.GA14592@redhat.com> On Tue, Nov 13 2018 at 7:51pm -0500, Jens Axboe wrote: > On 11/13/18 5:41 PM, Guenter Roeck wrote: > > Hi, > > > > On Wed, Oct 31, 2018@08:36:31AM -0600, Jens Axboe wrote: > >> NVMe does round-robin between queues by default, which means that > >> sharing a queue map for both reads and writes can be problematic > >> in terms of read servicing. It's much easier to flood the queue > >> with writes and reduce the read servicing. > >> > >> Implement two queue maps, one for reads and one for writes. The > >> write queue count is configurable through the 'write_queues' > >> parameter. > >> > >> By default, we retain the previous behavior of having a single > >> queue set, shared between reads and writes. Setting 'write_queues' > >> to a non-zero value will create two queue sets, one for reads and > >> one for writes, the latter using the configurable number of > >> queues (hardware queue counts permitting). > >> > >> Reviewed-by: Hannes Reinecke > >> Reviewed-by: Keith Busch > >> Signed-off-by: Jens Axboe > > > > This patch causes hangs when running recent versions of > > -next with several architectures; see the -next column at > > kerneltests.org/builders for details. Bisect log below; this > > was run with qemu on alpha. Reverting this patch as well as > > "nvme: add separate poll queue map" fixes the problem. > > I don't see anything related to what hung, the trace, and so on. > Can you clue me in? Where are the test results with dmesg? > > How to reproduce? Think Guenter should've provided a full kerneltests.org url, but I had a look and found this for powerpc with -next: https://kerneltests.org/builders/next-powerpc-next/builds/998/steps/buildcommand/logs/stdio Has useful logs of the build failure due to block. (not seeing any -next failure for alpha but Guenter said he was using qemu so the build failure could've been any arch qemu supports) Mike