Commit 4fe01c68 authored by Hidetoshi Seto's avatar Hidetoshi Seto Committed by Tony Luck
Browse files

[IA64] cleanup and improve fsys_gettimeofday 



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 - Remove outdated comments (which someday I marked with "?").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: default avatarHidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
parent cdeeeae0

arch/ia64/kernel/fsys.S

+12 −16
Original line number Diff line number Diff line
@@ -210,23 +210,21 @@ 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 are maybe outdated.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

	mov pr = r30,0xc000	// Set predicates according to function

	;;

	and r2 = TIF_ALLWORK_MASK,r2

(p6)    br.cond.spnt.few .fail_einval	// ? deferred branch

	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
@@ -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)

arch/ia64/kernel/patch.c

+4 −4
Original line number Diff line number Diff line
@@ -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;

	}

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