Messages in this thread | | | Date | Wed, 24 Mar 2010 12:15:19 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [patch 0/2] x86,pat: Reduce contention on the memtype_lock -V4 |
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On Wed, 24 Mar 2010, Robin Holt wrote: > On Wed, Mar 24, 2010 at 03:16:14AM +0100, Andi Kleen wrote: > > holt@sgi.com writes: > > > > > Tracking memtype on x86 uses a single global spin_lock for either reading > > > or changing the memory type. This includes changes made to page flags > > > which is perfectly parallel. > > > > > > Part one of the patchset makes the page-based tracking use cmpxchg > > > without a need for a lock. > > > > > > Part two of the patchset converts the spin_lock into a read/write lock. > > > > I'm curious: in what workloads did you see contention? > > > > For any scalability patches it would be always good to have a description > > of the workload. > > It was a job using xpmem (an out of tree kernel module) which uses > vm_insert_pfn to establish ptes. The scalability issues were shown > in the first patch. I do not have any test which shows a performance > difference with the spin_lock to rw_lock conversion.
And what's exactly the point of converting it to a rw_lock then ?
Thanks,
tglx
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