Messages in this thread | | | From | Linus Torvalds <> | Date | Wed, 23 Aug 2017 16:03:53 -0700 | Subject | Re: [PATCH] x86: enable RCU based table free when PARAVIRT |
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On Wed, Aug 23, 2017 at 3:36 PM, Kirill A. Shutemov <kirill.shutemov@linux.intel.com> wrote: > > Below is test cases that allocates a lot of page tables and measuare > fork/exit time. (I'm not entirely sure it's the best way to stress the > codepath.)
Looks ok to me. Doing a profile (without the RCU freeing, obviously) gives me
0.77% a.out [kernel.vmlinux] [k] free_pgd_range
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so it does seem to spend time in the page directory code.
> Unpatched: average 4.8322s, stddev 0.114s > Patched: average 4.8362s, stddev 0.111s
Ok, I vote for avoiding the complexity of two different behaviors, and just making the page table freeing use RCU unconditionally.
If actively trying to trigger that code doesn't show a real measurable difference, I don't think it matters, and the fewer different code paths we have, the better.
Linus
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