From: Santosh Sivaraj Date: Mon, 16 Oct 2017 05:49:14 +0000 (+0530) Subject: powerpc/vdso64: Add support for CLOCK_{REALTIME/MONOTONIC}_COARSE X-Git-Tag: v4.16-rc1~93^2~189 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=5c929885f1bb4b77f85b1769c49405a0e0f154a1;p=linux.git powerpc/vdso64: Add support for CLOCK_{REALTIME/MONOTONIC}_COARSE Current vDSO64 implementation does not have support for coarse clocks (CLOCK_MONOTONIC_COARSE, CLOCK_REALTIME_COARSE), for which it falls back to system call, increasing the response time, vDSO implementation reduces the cycle time. Below is a benchmark of the difference in execution times. (Non-coarse clocks are also included just for completion) clock-gettime-realtime: syscall: 172 nsec/call clock-gettime-realtime: libc: 28 nsec/call clock-gettime-realtime: vdso: 22 nsec/call clock-gettime-monotonic: syscall: 171 nsec/call clock-gettime-monotonic: libc: 30 nsec/call clock-gettime-monotonic: vdso: 25 nsec/call clock-gettime-realtime-coarse: syscall: 153 nsec/call clock-gettime-realtime-coarse: libc: 16 nsec/call clock-gettime-realtime-coarse: vdso: 10 nsec/call clock-gettime-monotonic-coarse: syscall: 167 nsec/call clock-gettime-monotonic-coarse: libc: 17 nsec/call clock-gettime-monotonic-coarse: vdso: 11 nsec/call CC: Benjamin Herrenschmidt Reviewed-by: Naveen N. Rao Signed-off-by: Santosh Sivaraj Signed-off-by: Michael Ellerman --- diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c index 6b958414b4e0..3f6316bcde4e 100644 --- a/arch/powerpc/kernel/asm-offsets.c +++ b/arch/powerpc/kernel/asm-offsets.c @@ -396,6 +396,8 @@ int main(void) /* Other bits used by the vdso */ DEFINE(CLOCK_REALTIME, CLOCK_REALTIME); DEFINE(CLOCK_MONOTONIC, CLOCK_MONOTONIC); + DEFINE(CLOCK_REALTIME_COARSE, CLOCK_REALTIME_COARSE); + DEFINE(CLOCK_MONOTONIC_COARSE, CLOCK_MONOTONIC_COARSE); DEFINE(NSEC_PER_SEC, NSEC_PER_SEC); DEFINE(CLOCK_REALTIME_RES, MONOTONIC_RES_NSEC); diff --git a/arch/powerpc/kernel/vdso64/gettimeofday.S b/arch/powerpc/kernel/vdso64/gettimeofday.S index 382021324883..c002adcc694c 100644 --- a/arch/powerpc/kernel/vdso64/gettimeofday.S +++ b/arch/powerpc/kernel/vdso64/gettimeofday.S @@ -64,6 +64,12 @@ V_FUNCTION_BEGIN(__kernel_clock_gettime) cmpwi cr0,r3,CLOCK_REALTIME cmpwi cr1,r3,CLOCK_MONOTONIC cror cr0*4+eq,cr0*4+eq,cr1*4+eq + + cmpwi cr5,r3,CLOCK_REALTIME_COARSE + cmpwi cr6,r3,CLOCK_MONOTONIC_COARSE + cror cr5*4+eq,cr5*4+eq,cr6*4+eq + + cror cr0*4+eq,cr0*4+eq,cr5*4+eq bne cr0,99f mflr r12 /* r12 saves lr */ @@ -72,6 +78,7 @@ V_FUNCTION_BEGIN(__kernel_clock_gettime) bl V_LOCAL_FUNC(__get_datapage) /* get data page */ lis r7,NSEC_PER_SEC@h /* want nanoseconds */ ori r7,r7,NSEC_PER_SEC@l + beq cr5,70f 50: bl V_LOCAL_FUNC(__do_get_tspec) /* get time from tb & kernel */ bne cr1,80f /* if not monotonic, all done */ @@ -97,19 +104,57 @@ V_FUNCTION_BEGIN(__kernel_clock_gettime) ld r0,CFG_TB_UPDATE_COUNT(r3) cmpld cr0,r0,r8 /* check if updated */ bne- 50b + b 78f - /* Add wall->monotonic offset and check for overflow or underflow. + /* + * For coarse clocks we get data directly from the vdso data page, so + * we don't need to call __do_get_tspec, but we still need to do the + * counter trick. */ - add r4,r4,r6 - add r5,r5,r9 - cmpd cr0,r5,r7 - cmpdi cr1,r5,0 - blt 1f - subf r5,r7,r5 - addi r4,r4,1 -1: bge cr1,80f - addi r4,r4,-1 - add r5,r5,r7 +70: ld r8,CFG_TB_UPDATE_COUNT(r3) + andi. r0,r8,1 /* pending update ? loop */ + bne- 70b + add r3,r3,r0 /* r0 is already 0 */ + + /* + * CLOCK_REALTIME_COARSE, below values are needed for MONOTONIC_COARSE + * too + */ + ld r4,STAMP_XTIME+TSPC64_TV_SEC(r3) + ld r5,STAMP_XTIME+TSPC64_TV_NSEC(r3) + bne cr6,75f + + /* CLOCK_MONOTONIC_COARSE */ + lwa r6,WTOM_CLOCK_SEC(r3) + lwa r9,WTOM_CLOCK_NSEC(r3) + + /* check if counter has updated */ + or r0,r6,r9 +75: or r0,r0,r4 + or r0,r0,r5 + xor r0,r0,r0 + add r3,r3,r0 + ld r0,CFG_TB_UPDATE_COUNT(r3) + cmpld cr0,r0,r8 /* check if updated */ + bne- 70b + + /* Counter has not updated, so continue calculating proper values for + * sec and nsec if monotonic coarse, or just return with the proper + * values for realtime. + */ + bne cr6,80f + + /* Add wall->monotonic offset and check for overflow or underflow */ +78: add r4,r4,r6 + add r5,r5,r9 + cmpd cr0,r5,r7 + cmpdi cr1,r5,0 + blt 79f + subf r5,r7,r5 + addi r4,r4,1 +79: bge cr1,80f + addi r4,r4,-1 + add r5,r5,r7 80: std r4,TSPC64_TV_SEC(r11) std r5,TSPC64_TV_NSEC(r11)