Messages in this thread | | | From | Andi Kleen <> | Subject | Re: [Patch 2/3] fast VMA recycling | Date | Thu, 23 Feb 2006 11:05:30 +0100 |
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On Thursday 23 February 2006 10:48, Arjan van de Ven wrote: > On Thu, 2006-02-23 at 10:42 +0100, Andi Kleen wrote: > > On Thursday 23 February 2006 10:30, Arjan van de Ven wrote: > > > This patch adds a per task-struct cache of a free vma. > > > > > > In normal operation, it is a really common action during userspace mmap > > > or malloc to first allocate a vma, and then find out that it can be merged, > > > and thus free it again. In fact this is the case roughly 95% of the time. > > > > > > In addition, this patch allows code to "prepopulate" the cache, and > > > this is done as example for the x86_64 mmap codepath. The advantage of this > > > prepopulation is that the memory allocation (which is a sleeping operation > > > due to the GFP_KERNEL flag, potentially causing either a direct sleep or a > > > voluntary preempt sleep) will happen before the mmap_sem is taken, and thus > > > reduces lock hold time (and thus the contention potential) > > > > The slab fast path doesn't sleep. > > it does via might_sleep()
Hmm? That shouldn't sleep.
If it takes any time in a real workload then it should move into DEBUG_KERNEL too. But I doubt it. Something with your analysis is wrong.
-Andi
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