Messages in this thread | | | Date | Tue, 16 Oct 2012 21:00:30 +1100 | Subject | Re: [PATCH 1/2] block: lift the initial queue bypass mode on blk_register_queue() instead of blk_init_allocated_queue() | From | Joseph Glanville <> |
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On 21 September 2012 23:25, Jens Axboe <axboe@kernel.dk> wrote: > On 09/20/2012 11:08 PM, Tejun Heo wrote: >> b82d4b197c ("blkcg: make request_queue bypassing on allocation") made >> request_queues bypassed on allocation to avoid switching on and off >> bypass mode on a queue being initialized. Some drivers allocate and >> then destroy a lot of queues without fully initializing them and >> incurring bypass latency overhead on each of them could add upto >> significant overhead. >> >> Unfortunately, blk_init_allocated_queue() is never used by queues of >> bio-based drivers, which means that all bio-based driver queues are in >> bypass mode even after initialization and registration complete >> successfully. >> >> Due to the limited way request_queues are used by bio drivers, this >> problem is hidden pretty well but it shows up when blk-throttle is >> used in combination with a bio-based driver. Trying to configure >> (echoing to cgroupfs file) blk-throttle for a bio-based driver hangs >> indefinitely in blkg_conf_prep() waiting for bypass mode to end. >> >> This patch moves the initial blk_queue_bypass_end() call from >> blk_init_allocated_queue() to blk_register_queue() which is called for >> any userland-visible queues regardless of its type. >> >> I believe this is correct because I don't think there is any block >> driver which needs or wants working elevator and blk-cgroup on a queue >> which isn't visible to userland. If there are such users, we need a >> different solution. >> >> Signed-off-by: Tejun Heo <tj@kernel.org> >> Reported-by: Joseph Glanville <joseph.glanville@orionvm.com.au> >> Cc: Vivek Goyal <vgoyal@redhat.com> >> Cc: stable@vger.kernel.org >> --- >> Jens, while these are fixes, I think it isn't extremely urgent and >> routing these through 3.7-rc1 should be enough. > > Agree, I'll shove them into for-3.7/core > > -- > Jens Axboe >
Hi,
Has this patch been marked for stable? This is still currently broken on 3.6.2 (and I would assume other stable kernels since 3.5)
Joseph.
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