Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [RFC][PATCH] PM: Force GFP_NOIO during suspend/resume (was: Re: [linux-pm] Memory allocations in .suspend became very unreliable) | Date | Mon, 18 Jan 2010 21:56:26 +0100 |
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On Monday 18 January 2010, Oliver Neukum wrote: > Am Montag, 18. Januar 2010 00:00:23 schrieb Rafael J. Wysocki: > > On Sunday 17 January 2010, Benjamin Herrenschmidt wrote: > > > On Sun, 2010-01-17 at 14:27 +0100, Rafael J. Wysocki wrote: > > ... > > > However, it's hard to deal with the case of allocations that have > > > already started waiting for IOs. It might be possible to have some VM > > > hook to make them wakeup, re-evaluate the situation and get out of that > > > code path but in any case it would be tricky. > > > > In the second version of the patch I used an rwsem that made us wait for these > > allocations to complete before we changed gfp_allowed_mask. > > This will be a very, very hot semaphore. What's the impact on performance?
rwsems are highly optimized AFAICT, but this is a good question of course.
I have no data at the moment.
Rafael
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