Minki/linux
1
0
Fork 1
mirror of https://github.com/torvalds/linux.git synced 2024-10-31 01:01:52 +00:00
Code Issues Packages Projects Releases Wiki Activity

[IA64] Reschedule __kernel_syscall_via_epc().

Browse Source 
Avoid some stalls, which is good for about 2 cycles when invoking a
light-weight handler.  When invoking a heavy-weight handler, this
helps by about 7 cycles, with most of the improvement coming from the
improved branch-prediction achieved by splitting the BBB bundle into
two MIB bundles.

Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
This commit is contained in:
David Mosberger-Tang 2005-04-27 21:19:37 -07:00 committed by Tony Luck
parent f8fa5448fc
commit 70929a57cf
1 changed files with 21 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

37
arch/ia64/kernel/gate.S
View File

@ -79,31 +79,34 @@ GLOBAL_ENTRY(__kernel_syscall_via_epc)
;;
rsm psr.be // note: on McKinley "rsm psr.be/srlz.d" is slightly faster than "rum psr.be"
LOAD_FSYSCALL_TABLE(r14)
;;
mov r16=IA64_KR(CURRENT) // 12 cycle read latency
tnat.nz p10,p9=r15
shladd r18=r17,3,r14
mov r19=NR_syscalls-1
;;
shladd r18=r17,3,r14
srlz.d
cmp.ne p8,p0=r0,r0 // p8 <- FALSE
lfetch [r18] // M0|1
mov r29=psr // read psr (12 cyc load latency)
/* Note: if r17 is a NaT, p6 will be set to zero. */
cmp.geu p6,p7=r19,r17 // (syscall > 0 && syscall < 1024+NR_syscalls)?
;;
(p6) ld8 r18=[r18]
mov r21=ar.fpsr
add r14=-8,r14 // r14 <- addr of fsys_bubble_down entry
;;
(p6) mov b7=r18
(p6) tbit.z p8,p0=r18,0
(p8) br.dptk.many b7
(p6) rsm psr.i
mov r27=ar.rsc
tnat.nz p10,p9=r15
mov r26=ar.pfs
;;
mov r29=psr // read psr (12 cyc load latency)
srlz.d
(p6) ld8 r18=[r18]
nop.i 0
;;
nop.m 0
(p6) mov b7=r18
(p6) tbit.z.unc p8,p0=r18,0
nop.m 0
nop.i 0
(p8) br.dptk.many b7
mov r27=ar.rsc
(p6) rsm psr.i
/*
* brl.cond doesn't work as intended because the linker would convert this branch
* into a branch to a PLT. Perhaps there will be a way to avoid this with some
@ -111,6 +114,8 @@ GLOBAL_ENTRY(__kernel_syscall_via_epc)
* instead.
*/
#ifdef CONFIG_ITANIUM
add r14=-8,r14 // r14 <- addr of fsys_bubble_down entry
;;
(p6) ld8 r14=[r14] // r14 <- fsys_bubble_down
;;
(p6) mov b7=r14