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| author | kib <kib@FreeBSD.org> | 2011-09-15 09:53:04 +0000 |
|---|---|---|
| committer | kib <kib@FreeBSD.org> | 2011-09-15 09:53:04 +0000 |
| commit | 747c6e1d12491b777c235cc4aea38bcaac9f2722 (patch) | |
| tree | 59ec0e24e5811939186235b3d9c2d73de2faadfd /sys/amd64/amd64/exception.S | |
| parent | 120983786685bae0ccfdf9aedce7cdaf65460803 (diff) | |
| download | FreeBSD-src-747c6e1d12491b777c235cc4aea38bcaac9f2722.zip FreeBSD-src-747c6e1d12491b777c235cc4aea38bcaac9f2722.tar.gz | |
Microoptimize the return path for the fast syscalls on amd64. Arrange
the code to have the fall-through path to follow the likely target.
Do not use intermediate register to reload user %rsp.
Proposed by: alc
Reviewed by: alc, jhb
Approved by: re (bz)
MFC after: 2 weeks
Diffstat (limited to 'sys/amd64/amd64/exception.S')
| -rw-r--r-- | sys/amd64/amd64/exception.S | 20 |
1 files changed, 10 insertions, 10 deletions
diff --git a/sys/amd64/amd64/exception.S b/sys/amd64/amd64/exception.S index 9f0c69a..89ad638 100644 --- a/sys/amd64/amd64/exception.S +++ b/sys/amd64/amd64/exception.S @@ -393,14 +393,8 @@ IDTVEC(fast_syscall) /* Check for and handle AST's on return to userland. */ movq PCPU(CURTHREAD),%rax testl $TDF_ASTPENDING | TDF_NEEDRESCHED,TD_FLAGS(%rax) - je 2f - sti - movq %rsp, %rdi - call ast - jmp 1b - - .align 16 -2: /* Restore preserved registers. */ + jne 2f + /* Restore preserved registers. */ MEXITCOUNT movq TF_RDI(%rsp),%rdi /* bonus; preserve arg 1 */ movq TF_RSI(%rsp),%rsi /* bonus: preserve arg 2 */ @@ -408,10 +402,16 @@ IDTVEC(fast_syscall) movq TF_RAX(%rsp),%rax /* return value 1 */ movq TF_RFLAGS(%rsp),%r11 /* original %rflags */ movq TF_RIP(%rsp),%rcx /* original %rip */ - movq TF_RSP(%rsp),%r9 /* user stack pointer */ - movq %r9,%rsp /* original %rsp */ + movq TF_RSP(%rsp),%rsp /* user stack pointer */ swapgs sysretq + +2: /* AST scheduled. */ + sti + movq %rsp,%rdi + call ast + jmp 1b + 3: /* Requested full context restore, use doreti for that. */ MEXITCOUNT jmp doreti |
