Messages in this thread | | | Date | Fri, 2 Jul 2010 03:23:17 +1000 | From | Nick Piggin <> | Subject | Re: [patch 00/52] vfs scalability patches updated |
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On Wed, Jun 30, 2010 at 10:40:49PM +1000, Nick Piggin wrote: > But actually it's not all for scalability. I have some follow on patches > (that require RCU inodes, among other things) that actually improve > single threaded performance significnatly. git diff workload IIRC was > several % improved from speeding up stat(2).
I rewrote the store-free path walk patch that goes on top of this patchset (it's now much cleaner and more optimised, I'll post a patch soonish). It is quicker than I remembered.
A single thread running stat(2) in a loop on a file "./file" has the following cost (on an 2s8c Barcelona):
2.6.35-rc3 595 ns/op patched 336 ns/op
stat(2) takes 56% the time with patches. It's something like 13 fewer atomic operations per syscall.
What's that good for? A single threaded, cached `git diff` on the linux kernel tree takes just 81% of the time after the vfs patches (0.27s vs 0.33s).
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