Author: kib
Date: Sun Sep 11 16:08:10 2011
New Revision: 225475
URL: http://svn.freebsd.org/changeset/base/225475
Log:
Perform amd64-specific microoptimizations for native syscall entry
sequence. The effect is ~1% on the microbenchmark.
In particular, do not restore registers which are preserved by the
C calling sequence. Align the jump target. Avoid unneeded memory
accesses by calculating some data in syscall entry trampoline.
Reviewed by: jhb
Approved by: re (bz)
MFC after: 2 weeks
Modified:
head/sys/amd64/amd64/exception.S
head/sys/amd64/amd64/genassym.c
head/sys/amd64/amd64/trap.c
Modified: head/sys/amd64/amd64/exception.S
==============================================================================
--- head/sys/amd64/amd64/exception.S Sun Sep 11 16:05:09 2011
(r225474)
+++ head/sys/amd64/amd64/exception.S Sun Sep 11 16:08:10 2011
(r225475)
@@ -380,8 +380,11 @@ IDTVEC(fast_syscall)
movl $TF_HASSEGS,TF_FLAGS(%rsp)
cld
FAKE_MCOUNT(TF_RIP(%rsp))
- movq %rsp,%rdi
- call syscall
+ movq PCPU(CURTHREAD),%rdi
+ movq %rsp,TD_FRAME(%rdi)
+ movl TF_RFLAGS(%rsp),%esi
+ andl $PSL_T,%esi
+ call amd64_syscall
1: movq PCPU(CURPCB),%rax
/* Disable interrupts before testing PCB_FULL_IRET. */
cli
@@ -396,17 +399,12 @@ IDTVEC(fast_syscall)
call ast
jmp 1b
2: /* Restore preserved registers. */
+ .align 16
MEXITCOUNT
movq TF_RDI(%rsp),%rdi /* bonus; preserve arg 1 */
movq TF_RSI(%rsp),%rsi /* bonus: preserve arg 2 */
movq TF_RDX(%rsp),%rdx /* return value 2 */
movq TF_RAX(%rsp),%rax /* return value 1 */
- movq TF_RBX(%rsp),%rbx /* C preserved */
- movq TF_RBP(%rsp),%rbp /* C preserved */
- movq TF_R12(%rsp),%r12 /* C preserved */
- movq TF_R13(%rsp),%r13 /* C preserved */
- movq TF_R14(%rsp),%r14 /* C preserved */
- movq TF_R15(%rsp),%r15 /* C preserved */
movq TF_RFLAGS(%rsp),%r11 /* original %rflags */
movq TF_RIP(%rsp),%rcx /* original %rip */
movq TF_RSP(%rsp),%r9 /* user stack pointer */
Modified: head/sys/amd64/amd64/genassym.c
==============================================================================
--- head/sys/amd64/amd64/genassym.c Sun Sep 11 16:05:09 2011
(r225474)
+++ head/sys/amd64/amd64/genassym.c Sun Sep 11 16:08:10 2011
(r225475)
@@ -87,6 +87,7 @@ ASSYM(TD_PCB, offsetof(struct thread, td
ASSYM(TD_PFLAGS, offsetof(struct thread, td_pflags));
ASSYM(TD_PROC, offsetof(struct thread, td_proc));
ASSYM(TD_TID, offsetof(struct thread, td_tid));
+ASSYM(TD_FRAME, offsetof(struct thread, td_frame));
ASSYM(TDF_ASTPENDING, TDF_ASTPENDING);
ASSYM(TDF_NEEDRESCHED, TDF_NEEDRESCHED);
Modified: head/sys/amd64/amd64/trap.c
==============================================================================
--- head/sys/amd64/amd64/trap.c Sun Sep 11 16:05:09 2011 (r225474)
+++ head/sys/amd64/amd64/trap.c Sun Sep 11 16:08:10 2011 (r225475)
@@ -885,41 +885,36 @@ cpu_fetch_syscall_args(struct thread *td
#include "../../kern/subr_syscall.c"
+void amd64_syscall(struct thread *td, int traced);
/*
* syscall - system call request C handler
*
* A system call is essentially treated as a trap.
*/
void
-syscall(struct trapframe *frame)
+amd64_syscall(struct thread *td, int traced)
{
- struct thread *td;
struct syscall_args sa;
- register_t orig_tf_rflags;
int error;
ksiginfo_t ksi;
#ifdef DIAGNOSTIC
- if (ISPL(frame->tf_cs) != SEL_UPL) {
+ if (ISPL(td->td_frame->tf_cs) != SEL_UPL) {
panic("syscall");
/* NOT REACHED */
}
#endif
- orig_tf_rflags = frame->tf_rflags;
- td = curthread;
- td->td_frame = frame;
-
error = syscallenter(td, &sa);
/*
* Traced syscall.
*/
- if (orig_tf_rflags & PSL_T) {
- frame->tf_rflags &= ~PSL_T;
+ if (__predict_false(traced)) {
+ td->td_frame->tf_rflags &= ~PSL_T;
ksiginfo_init_trap(&ksi);
ksi.ksi_signo = SIGTRAP;
ksi.ksi_code = TRAP_TRACE;
- ksi.ksi_addr = (void *)frame->tf_rip;
+ ksi.ksi_addr = (void *)td->td_frame->tf_rip;
trapsignal(td, &ksi);
}
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