Christophe Leroy <christophe.le...@c-s.fr> writes: > Le 21/08/2019 à 11:29, Santosh Sivaraj a écrit : >> __get_datapage() is only a few instructions to retrieve the >> address of the page where the kernel stores data to the VDSO. >> >> By inlining this function into its users, a bl/blr pair and >> a mflr/mtlr pair is avoided, plus a few reg moves. >> >> clock-gettime-monotonic: syscall: 514 nsec/call 396 nsec/call >> clock-gettime-monotonic: libc: 25 nsec/call 24 nsec/call >> clock-gettime-monotonic: vdso: 20 nsec/call 20 nsec/call >> clock-getres-monotonic: syscall: 347 nsec/call 372 nsec/call >> clock-getres-monotonic: libc: 19 nsec/call 19 nsec/call >> clock-getres-monotonic: vdso: 10 nsec/call 10 nsec/call >> clock-gettime-monotonic-coarse: syscall: 511 nsec/call 396 nsec/call >> clock-gettime-monotonic-coarse: libc: 23 nsec/call 21 nsec/call >> clock-gettime-monotonic-coarse: vdso: 15 nsec/call 13 nsec/call >> clock-gettime-realtime: syscall: 526 nsec/call 405 nsec/call >> clock-gettime-realtime: libc: 24 nsec/call 23 nsec/call >> clock-gettime-realtime: vdso: 18 nsec/call 18 nsec/call >> clock-getres-realtime: syscall: 342 nsec/call 372 nsec/call >> clock-getres-realtime: libc: 19 nsec/call 19 nsec/call >> clock-getres-realtime: vdso: 10 nsec/call 10 nsec/call >> clock-gettime-realtime-coarse: syscall: 515 nsec/call 373 nsec/call >> clock-gettime-realtime-coarse: libc: 23 nsec/call 22 nsec/call >> clock-gettime-realtime-coarse: vdso: 14 nsec/call 13 nsec/call > > I think you should only put the measurements on vdso calls, and only the > ones that are impacted by the change. For exemple, getres function > doesn't use __get_datapage so showing it here is pointless. > > gettimeofday should be shown there as it uses __get_datapage() > > >> >> Based on the patch by Christophe Leroy <christophe.le...@c-s.fr> for vdso32. >> >> Signed-off-by: Santosh Sivaraj <sant...@fossix.org> >> --- >> >> except for a couple of calls (1 or 2 nsec reduction), there are no >> improvements in the call times. Or is 10 nsec the minimum granularity?? > > Maybe the ones that show no improvements are the ones that don't use > __get_datapage() at all ...
Yes makes sense. > >> >> So I don't know if its even worth updating vdso64 except to keep vdso32 and >> vdso64 equal. > > 2ns on a 15ns call is 13% so it is worth it I think. true. Since datapage.h is the same for both 32 and 64, may be we should put it in include/asm. Thanks, Santosh > > Christophe > > >> >> >> arch/powerpc/kernel/vdso64/cacheflush.S | 10 ++++---- >> arch/powerpc/kernel/vdso64/datapage.S | 29 ++++------------------- >> arch/powerpc/kernel/vdso64/datapage.h | 10 ++++++++ >> arch/powerpc/kernel/vdso64/gettimeofday.S | 8 ++++--- >> 4 files changed, 24 insertions(+), 33 deletions(-) >> create mode 100644 arch/powerpc/kernel/vdso64/datapage.h >> >> diff --git a/arch/powerpc/kernel/vdso64/cacheflush.S >> b/arch/powerpc/kernel/vdso64/cacheflush.S >> index 3f92561a64c4..30e8b0d29bea 100644 >> --- a/arch/powerpc/kernel/vdso64/cacheflush.S >> +++ b/arch/powerpc/kernel/vdso64/cacheflush.S >> @@ -10,6 +10,8 @@ >> #include <asm/vdso.h> >> #include <asm/asm-offsets.h> >> >> +#include "datapage.h" >> + >> .text >> >> /* >> @@ -24,14 +26,12 @@ V_FUNCTION_BEGIN(__kernel_sync_dicache) >> .cfi_startproc >> mflr r12 >> .cfi_register lr,r12 >> - mr r11,r3 >> - bl V_LOCAL_FUNC(__get_datapage) >> + get_datapage r11, r0 >> mtlr r12 >> - mr r10,r3 >> >> lwz r7,CFG_DCACHE_BLOCKSZ(r10) >> addi r5,r7,-1 >> - andc r6,r11,r5 /* round low to line bdy */ >> + andc r6,r3,r5 /* round low to line bdy */ >> subf r8,r6,r4 /* compute length */ >> add r8,r8,r5 /* ensure we get enough */ >> lwz r9,CFG_DCACHE_LOGBLOCKSZ(r10) >> @@ -48,7 +48,7 @@ V_FUNCTION_BEGIN(__kernel_sync_dicache) >> >> lwz r7,CFG_ICACHE_BLOCKSZ(r10) >> addi r5,r7,-1 >> - andc r6,r11,r5 /* round low to line bdy */ >> + andc r6,r3,r5 /* round low to line bdy */ >> subf r8,r6,r4 /* compute length */ >> add r8,r8,r5 >> lwz r9,CFG_ICACHE_LOGBLOCKSZ(r10) >> diff --git a/arch/powerpc/kernel/vdso64/datapage.S >> b/arch/powerpc/kernel/vdso64/datapage.S >> index dc84f5ae3802..8712f57c931c 100644 >> --- a/arch/powerpc/kernel/vdso64/datapage.S >> +++ b/arch/powerpc/kernel/vdso64/datapage.S >> @@ -11,34 +11,13 @@ >> #include <asm/unistd.h> >> #include <asm/vdso.h> >> >> +#include "datapage.h" >> + >> .text >> .global __kernel_datapage_offset; >> __kernel_datapage_offset: >> .long 0 >> >> -V_FUNCTION_BEGIN(__get_datapage) >> - .cfi_startproc >> - /* We don't want that exposed or overridable as we want other objects >> - * to be able to bl directly to here >> - */ >> - .protected __get_datapage >> - .hidden __get_datapage >> - >> - mflr r0 >> - .cfi_register lr,r0 >> - >> - bcl 20,31,data_page_branch >> -data_page_branch: >> - mflr r3 >> - mtlr r0 >> - addi r3, r3, __kernel_datapage_offset-data_page_branch >> - lwz r0,0(r3) >> - .cfi_restore lr >> - add r3,r0,r3 >> - blr >> - .cfi_endproc >> -V_FUNCTION_END(__get_datapage) >> - >> /* >> * void *__kernel_get_syscall_map(unsigned int *syscall_count) ; >> * >> @@ -53,7 +32,7 @@ V_FUNCTION_BEGIN(__kernel_get_syscall_map) >> mflr r12 >> .cfi_register lr,r12 >> mr r4,r3 >> - bl V_LOCAL_FUNC(__get_datapage) >> + get_datapage r3, r0 >> mtlr r12 >> addi r3,r3,CFG_SYSCALL_MAP64 >> cmpldi cr0,r4,0 >> @@ -75,7 +54,7 @@ V_FUNCTION_BEGIN(__kernel_get_tbfreq) >> .cfi_startproc >> mflr r12 >> .cfi_register lr,r12 >> - bl V_LOCAL_FUNC(__get_datapage) >> + get_datapage r3, r0 >> ld r3,CFG_TB_TICKS_PER_SEC(r3) >> mtlr r12 >> crclr cr0*4+so >> diff --git a/arch/powerpc/kernel/vdso64/datapage.h >> b/arch/powerpc/kernel/vdso64/datapage.h >> new file mode 100644 >> index 000000000000..f2f0da0f65f3 >> --- /dev/null >> +++ b/arch/powerpc/kernel/vdso64/datapage.h >> @@ -0,0 +1,10 @@ >> +/* SPDX-License-Identifier: GPL-2.0-or-later */ >> + >> +.macro get_datapage ptr, tmp >> + bcl 20,31,888f >> +888: >> + mflr \ptr >> + addi \ptr, \ptr, __kernel_datapage_offset - 888b >> + lwz \tmp, 0(\ptr) >> + add \ptr, \tmp, \ptr >> +.endm >> diff --git a/arch/powerpc/kernel/vdso64/gettimeofday.S >> b/arch/powerpc/kernel/vdso64/gettimeofday.S >> index 07bfe33fe874..7bcc879392cc 100644 >> --- a/arch/powerpc/kernel/vdso64/gettimeofday.S >> +++ b/arch/powerpc/kernel/vdso64/gettimeofday.S >> @@ -12,6 +12,8 @@ >> #include <asm/asm-offsets.h> >> #include <asm/unistd.h> >> >> +#include "datapage.h" >> + >> .text >> /* >> * Exact prototype of gettimeofday >> @@ -26,7 +28,7 @@ V_FUNCTION_BEGIN(__kernel_gettimeofday) >> >> mr r11,r3 /* r11 holds tv */ >> mr r10,r4 /* r10 holds tz */ >> - bl V_LOCAL_FUNC(__get_datapage) /* get data page */ >> + get_datapage r3, r0 >> cmpldi r11,0 /* check if tv is NULL */ >> beq 2f >> lis r7,1000000@ha /* load up USEC_PER_SEC */ >> @@ -71,7 +73,7 @@ V_FUNCTION_BEGIN(__kernel_clock_gettime) >> mflr r12 /* r12 saves lr */ >> .cfi_register lr,r12 >> mr r11,r4 /* r11 saves tp */ >> - bl V_LOCAL_FUNC(__get_datapage) /* get data page */ >> + get_datapage r3, r0 /* get data page */ >> lis r7,NSEC_PER_SEC@h /* want nanoseconds */ >> ori r7,r7,NSEC_PER_SEC@l >> beq cr5,70f >> @@ -218,7 +220,7 @@ V_FUNCTION_BEGIN(__kernel_time) >> .cfi_register lr,r12 >> >> mr r11,r3 /* r11 holds t */ >> - bl V_LOCAL_FUNC(__get_datapage) >> + get_datapage r3, r0 >> >> ld r4,STAMP_XTIME+TSPC64_TV_SEC(r3) >> >>
