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[IA64] cleanup and improve fsys_gettimeofday

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This patch does:

 - Remove outdated comments (which someday I marked with "?").
 - Reassemble instructions to fit them in fewer bundles.
 - If McKinley Errata 9 workaround is not needed, the workaround
   bundles will be patched out with NOPs. However it also not
   needed to have a totally NOP bundle (nop * 3) before branch.

As a result, this makes the code path 3 (or 2) bundles shorter
(and remove 1 unnecessary stop bit). It seems to be 1% faster.

(10sec loop test, with nojitter @ Madison 1.5GHz x 4)
Before:
 CPU  0:  0.14 (usecs) (0 errors / 69598875 iterations)
 CPU  1:  0.14 (usecs) (0 errors / 69630721 iterations)
 CPU  2:  0.14 (usecs) (0 errors / 69607850 iterations)
 CPU  3:  0.14 (usecs) (0 errors / 69619832 iterations)

After:
 CPU  0:  0.14 (usecs) (0 errors / 70257728 iterations)
 CPU  1:  0.14 (usecs) (0 errors / 70309498 iterations)
 CPU  2:  0.14 (usecs) (0 errors / 70280639 iterations)
 CPU  3:  0.14 (usecs) (0 errors / 70260682 iterations)

Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
This commit is contained in:
Hidetoshi Seto 2008-01-29 14:39:33 +09:00 committed by Tony Luck
parent cdeeeae056
commit 4fe01c68eb
2 changed files with 17 additions and 21 deletions
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30
arch/ia64/kernel/fsys.S
View File

@ -210,27 +210,25 @@ ENTRY(fsys_gettimeofday)
// Note that instructions are optimized for McKinley. McKinley can
// process two bundles simultaneously and therefore we continuously
// try to feed the CPU two bundles and then a stop.
//
// Additional note that code has changed a lot. Optimization is TBD.
// Comments begin with "?" are maybe outdated.
tnat.nz p6,p0 = r31 // ? branch deferred to fit later bundle
mov pr = r30,0xc000 // Set predicates according to function
add r2 = TI_FLAGS+IA64_TASK_SIZE,r16
tnat.nz p6,p0 = r31 // guard against Nat argument
(p6) br.cond.spnt.few .fail_einval
movl r20 = fsyscall_gtod_data // load fsyscall gettimeofday data address
;;
ld4 r2 = [r2] // process work pending flags
movl r29 = itc_jitter_data // itc_jitter
add r22 = IA64_GTOD_WALL_TIME_OFFSET,r20 // wall_time
ld4 r2 = [r2] // process work pending flags
;;
(p15) add r22 = IA64_GTOD_MONO_TIME_OFFSET,r20 // monotonic_time
add r21 = IA64_CLKSRC_MMIO_OFFSET,r20
add r19 = IA64_ITC_LASTCYCLE_OFFSET,r29
and r2 = TIF_ALLWORK_MASK,r2
(p6) br.cond.spnt.few .fail_einval // ? deferred branch
mov pr = r30,0xc000 // Set predicates according to function
;;
add r26 = IA64_CLKSRC_CYCLE_LAST_OFFSET,r20 // clksrc_cycle_last
and r2 = TIF_ALLWORK_MASK,r2
add r19 = IA64_ITC_LASTCYCLE_OFFSET,r29
(p15) add r22 = IA64_GTOD_MONO_TIME_OFFSET,r20 // monotonic_time
;;
add r26 = IA64_CLKSRC_CYCLE_LAST_OFFSET,r20 // clksrc_cycle_last
cmp.ne p6, p0 = 0, r2 // Fallback if work is scheduled
(p6) br.cond.spnt.many fsys_fallback_syscall
(p6) br.cond.spnt.many fsys_fallback_syscall
;;
// Begin critical section
.time_redo:
@ -258,7 +256,6 @@ ENTRY(fsys_gettimeofday)
(p8) mov r2 = ar.itc // CPU_TIMER. 36 clocks latency!!!
(p9) ld8 r2 = [r30] // MMIO_TIMER. Could also have latency issues..
(p13) ld8 r25 = [r19] // get itc_lastcycle value
;; // ? could be removed by moving the last add upward
ld8 r9 = [r22],IA64_TIMESPEC_TV_NSEC_OFFSET // tv_sec
;;
ld8 r8 = [r22],-IA64_TIMESPEC_TV_NSEC_OFFSET // tv_nsec
@ -285,13 +282,12 @@ ENTRY(fsys_gettimeofday)
EX(.fail_efault, probe.w.fault r31, 3)
xmpy.l f8 = f8,f7 // nsec_per_cyc*(counter-last_counter)
;;
// ? simulate tbit.nz.or p7,p0 = r28,0
getf.sig r2 = f8
mf
;;
ld4 r10 = [r20] // gtod_lock.sequence
shr.u r2 = r2,r23 // shift by factor
;; // ? overloaded 3 bundles!
;;
add r8 = r8,r2 // Add xtime.nsecs
cmp4.ne p7,p0 = r28,r10
(p7) br.cond.dpnt.few .time_redo // sequence number changed, redo
@ -319,9 +315,9 @@ EX(.fail_efault, probe.w.fault r31, 3)
EX(.fail_efault, probe.w.fault r23, 3) // This also costs 5 cycles
(p14) xmpy.hu f8 = f8, f7 // xmpy has 5 cycles latency so use it
;;
mov r8 = r0
(p14) getf.sig r2 = f8
;;
mov r8 = r0
(p14) shr.u r21 = r2, 4
;;
EX(.fail_efault, st8 [r31] = r9)

8
arch/ia64/kernel/patch.c
View File

@ -135,10 +135,10 @@ ia64_patch_mckinley_e9 (unsigned long start, unsigned long end)
while (offp < (s32 *) end) {
wp = (u64 *) ia64_imva((char *) offp + *offp);
wp[0] = 0x0000000100000000UL; /* nop.m 0; nop.i 0; nop.i 0 */
wp[1] = 0x0004000000000200UL;
wp[2] = 0x0000000100000011UL; /* nop.m 0; nop.i 0; br.ret.sptk.many b6 */
wp[3] = 0x0084006880000200UL;
wp[0] = 0x0000000100000011UL; /* nop.m 0; nop.i 0; br.ret.sptk.many b6 */
wp[1] = 0x0084006880000200UL;
wp[2] = 0x0000000100000000UL; /* nop.m 0; nop.i 0; nop.i 0 */
wp[3] = 0x0004000000000200UL;
ia64_fc(wp); ia64_fc(wp + 2);
++offp;
}