Messages in this thread |  | | Date | Wed, 22 Jun 2011 18:04:39 +0200 | | From | Jens Axboe <> | | Subject | Re: [RFC][PATCH 1/3] sched, block: Move unplug |
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On 2011-06-22 17:08, Vivek Goyal wrote: > On Wed, Jun 22, 2011 at 04:38:01PM +0200, Peter Zijlstra wrote: >> On Wed, 2011-06-22 at 16:30 +0200, Thomas Gleixner wrote: >>>> It is supposedly a real problem, not just an inkling. It's not about >>>> recursing indefinitely, the plug is fairly bounded. But the IO dispatch >>>> path can be pretty deep, and if you hit that deep inside the reclaim or >>>> file system write path, then you get dangerously close. Dave Chinner >>>> posted some numbers in the 2.6.39-rc1 time frame showing how close we >>>> got. >>> >>> Fair enough. >> >>> Ok. So we move it out and keep the from_scheduler flag so that code >>> does not go down the IO path from there. >> >> Won't punting the plug to a worker thread wreck all kinds of io >> accounting due to the wrong task doing the actual io submission? > > I think all the accounting will the done in IO submission path and > while IO is added to plug. This is just plug flush so should not > have effect on accounting.
Exactly, this is just the insert operation, so no worries there. The request are fully "formulated".
-- Jens Axboe
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