Messages in this thread | | | Date | Wed, 20 Nov 2019 16:17:41 +0100 | From | Christophe Leroy <> | Subject | Re: [PATCH v3 2/8] powerpc/vdso32: Add support for CLOCK_{REALTIME/MONOTONIC}_COARSE |
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Michael Ellerman <mpe@ellerman.id.au> a écrit :
> Christophe Leroy <christophe.leroy@c-s.fr> writes: >> This is copied and adapted from commit 5c929885f1bb ("powerpc/vdso64: >> Add support for CLOCK_{REALTIME/MONOTONIC}_COARSE") >> from Santosh Sivaraj <santosh@fossix.org> >> >> Benchmark from vdsotest-all: >> clock-gettime-realtime: syscall: 3601 nsec/call >> clock-gettime-realtime: libc: 1072 nsec/call >> clock-gettime-realtime: vdso: 931 nsec/call >> clock-gettime-monotonic: syscall: 4034 nsec/call >> clock-gettime-monotonic: libc: 1213 nsec/call >> clock-gettime-monotonic: vdso: 1076 nsec/call >> clock-gettime-realtime-coarse: syscall: 2722 nsec/call >> clock-gettime-realtime-coarse: libc: 805 nsec/call >> clock-gettime-realtime-coarse: vdso: 668 nsec/call >> clock-gettime-monotonic-coarse: syscall: 2949 nsec/call >> clock-gettime-monotonic-coarse: libc: 882 nsec/call >> clock-gettime-monotonic-coarse: vdso: 745 nsec/call >> >> Additional test passed with: >> vdsotest -d 30 clock-gettime-monotonic-coarse verify > > This broke on 64-bit big endian, which uses the 32-bit VDSO, with errors > like: > > clock-gettime-monotonic-coarse/verify: 10 failures/inconsistencies > encountered > timestamp obtained from libc/vDSO not normalized: > [-1574202155, 1061008673] > timestamp obtained from libc/vDSO predates timestamp > previously obtained from kernel: > [74, 261310747] (kernel) > [-1574202155, 1061008673] (vDSO) > timestamp obtained from libc/vDSO not normalized: > [-1574202155, 1061008673] > timestamp obtained from libc/vDSO predates timestamp > previously obtained from kernel: > [74, 261310747] (kernel) > [-1574202155, 1061008673] (vDSO) > timestamp obtained from libc/vDSO not normalized: > [-1574202155, 1061008673] > timestamp obtained from libc/vDSO predates timestamp > previously obtained from kernel: > [74, 261310747] (kernel) > [-1574202155, 1061008673] (vDSO) > timestamp obtained from libc/vDSO not normalized: > [-1574202155, 1061008673] > timestamp obtained from libc/vDSO predates timestamp > previously obtained from kernel: > [74, 261310747] (kernel) > [-1574202155, 1061008673] (vDSO) > timestamp obtained from libc/vDSO not normalized: > [-1574202155, 1061008673] > timestamp obtained from libc/vDSO predates timestamp > previously obtained from kernel: > [74, 261310747] (kernel) > [-1574202155, 1061008673] (vDSO) > Failure threshold (10) reached; stopping test. > > > The diff below seems to fix it, but I'm not sure it's correct. ie. we > just ignore the top part of the values, how does that work?
Your change makes sense, it is consistent with other functions using STAMP_XTIME.
It works because nanoseconds are max 999999999, it fits 32 bits regs.
Christophe
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