Messages in this thread | | | Date | Tue, 06 Nov 2007 05:08:07 -0500 | From | Chris Snook <> | Subject | Re: [RFC/PATCH] Optimize zone allocator synchronization |
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Don Porter wrote: > From: Donald E. Porter <porterde@cs.utexas.edu> > > In the bulk page allocation/free routines in mm/page_alloc.c, the zone > lock is held across all iterations. For certain parallel workloads, I > have found that releasing and reacquiring the lock for each iteration > yields better performance, especially at higher CPU counts. For > instance, kernel compilation is sped up by 5% on an 8 CPU test > machine. In most cases, there is no significant effect on performance > (although the effect tends to be slightly positive). This seems quite > reasonable for the very small scope of the change. > > My intuition is that this patch prevents smaller requests from waiting > on larger ones. While grabbing and releasing the lock within the loop > adds a few instructions, it can lower the latency for a particular > thread's allocation which is often on the thread's critical path. > Lowering the average latency for allocation can increase system throughput. > > More detailed information, including data from the tests I ran to > validate this change are available at > http://www.cs.utexas.edu/~porterde/kernel-patch.html . > > Thanks in advance for your consideration and feedback.
That's an interesting insight. My intuition is that Nick Piggin's recently-posted ticket spinlocks patches[1] will reduce the need for this patch, though it may be useful to have both. Can you benchmark again with only ticket spinlocks, and with ticket spinlocks + this patch? You'll probably want to use 2.6.24-rc1 as your baseline, due to the x86 architecture merge.
-- Chris
[1] http://lkml.org/lkml/2007/11/1/123 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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