svn commit: r220430 - head/sys/amd64/amd64
Jung-uk Kim
jkim at FreeBSD.org
Thu Apr 7 21:52:09 UTC 2011
On Thursday 07 April 2011 05:32 pm, John Baldwin wrote:
> Author: jhb
> Date: Thu Apr 7 21:32:25 2011
> New Revision: 220430
> URL: http://svn.freebsd.org/changeset/base/220430
>
> Log:
> If a system call does not request a full interrupt return, use a
> fast path via the sysretq instruction to return from the system
> call. This was removed in 190620 and not quite fully restored in
> 195486. This resolves most of the performance regression in system
> call microbenchmarks between 7 and 8 on amd64.
>
> Reviewed by: kib
> MFC after: 1 week
>
> Modified:
> head/sys/amd64/amd64/exception.S
>
> Modified: head/sys/amd64/amd64/exception.S
> ===================================================================
>=========== --- head/sys/amd64/amd64/exception.S Thu Apr 7 21:29:34
> 2011 (r220429) +++ head/sys/amd64/amd64/exception.S Thu Apr 7
> 21:32:25 2011 (r220430) @@ -339,6 +339,9 @@ IDTVEC(prot)
> * and the new privilige level. We are still running on the old
> user stack * pointer. We have to juggle a few things around to
> find our stack etc. * swapgs gives us access to our PCPU space
> only.
> + *
> + * We do not support invoking this from a custom %cs or %ss (e.g.
> using + * entries from an LDT).
> */
> IDTVEC(fast_syscall)
> swapgs
> @@ -380,6 +383,36 @@ IDTVEC(fast_syscall)
> movq %rsp,%rdi
> call syscall
> movq PCPU(CURPCB),%rax
> + testq $PCB_FULL_IRET,PCB_FLAGS(%rax)
FYI, pcb_flags is u_int now, i.e., we need testl here.
Jung-uk Kim
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