From: Christoph Hellwig <hch@infradead.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: Kent Overstreet <kmo@daterainc.com>,
Ming Lei <tom.leiming@gmail.com>,
Alexander Gordeev <agordeev@redhat.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Shaohua Li <shli@kernel.org>,
Nicholas Bellinger <nab@linux-iscsi.org>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH RFC 0/2] percpu_ida: Take into account CPU topology when stealing tags
Date: Thu, 1 May 2014 22:05:23 -0700 [thread overview]
Message-ID: <20140502050523.GA21708@infradead.org> (raw)
In-Reply-To: <536300BB.5060906@kernel.dk>
On Thu, May 01, 2014 at 08:19:39PM -0600, Jens Axboe wrote:
> I've taken the consequence of this and implemented another tagging
> scheme that blk-mq will use if it deems that percpu_ida isn't going
> to be effective for the device being initialized. But I really hate
> to have both of them in there. Unfortunately I have no devices
> available that have a tag space that will justify using percu_ida,
> so comparisons are a bit hard at the moment. NVMe should change
> that, though, so decision will have to be deferred until that is
> tested.
At least for SCSI devices _tag space_ is plenty, it's just the we
artifically limit our tag space to the queue depth to avoid having to
track that one separately. In addition we also preallocaste a request
for each tag, so even if we would track the queue depth separately
we would waste a lot of memory.
next prev parent reply other threads:[~2014-05-02 5:05 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-26 13:34 [PATCH RFC 0/2] percpu_ida: Take into account CPU topology when stealing tags Alexander Gordeev
2014-03-26 13:34 ` [PATCH RFC 1/2] sched: Introduce topology level masks and for_each_tlm() macro Alexander Gordeev
2014-03-26 13:34 ` [PATCH RFC 2/2] percpu_ida: Use for_each_tlm() macro for CPU lookup in steal_tags() Alexander Gordeev
2014-04-22 7:10 ` [PATCH RFC 0/2] percpu_ida: Take into account CPU topology when stealing tags Alexander Gordeev
2014-04-22 14:03 ` Jens Axboe
2014-04-22 15:57 ` Jens Axboe
2014-04-23 0:53 ` Ming Lei
2014-04-23 1:25 ` Jens Axboe
2014-04-25 9:10 ` Ming Lei
2014-04-25 21:23 ` Jens Axboe
2014-04-26 0:01 ` Ming Lei
2014-04-26 2:03 ` Jens Axboe
2014-04-29 11:35 ` Ming Lei
2014-04-29 21:13 ` Jens Axboe
2014-04-30 9:40 ` Ming Lei
2014-05-01 22:47 ` Kent Overstreet
2014-05-02 2:19 ` Jens Axboe
2014-05-02 2:38 ` Kent Overstreet
2014-05-02 2:44 ` Jens Axboe
2014-05-02 5:05 ` Christoph Hellwig [this message]
2014-05-02 16:41 ` Jens Axboe
2014-05-02 16:43 ` Christoph Hellwig
2014-05-02 16:56 ` Jens Axboe
2014-04-22 11:56 ` Peter Zijlstra
2014-05-01 21:24 ` Alexander Gordeev
2014-05-01 22:04 ` Alexander Gordeev
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