Hi, merge window is about to close so I hope it's OK to make another try here. Changes since v2: - Add explicit READ_ONCE() to not rely on 'volatile' [Andy Lutomirski] - rdtsc() -> rdtsc_ordered() [Andy Lutomirski] - virt_rmb() -> smp_rmb() [Thomas Gleixner, Andy Lutomirski] Thomas, Andy, it seems the only blocker for the series was the ambiguity with TSC page read algorithm. I contacted Microsoft (through K. Y.) and asked what we should do when we see 'seq=0'. The answer is: "I have confirmed that the only invalid value is 0 (notwithstanding what the spec says). I have asked the Spec to be updated and the current code we have is correct - it treats 0 as the only invalid value. The invalid value indicates that the TSC page cannot be used as a time source and a different source is to be used and this state is going to persist and so looping is not an option." I agree it would be wiser to have two invalid values - one for 'try again' and another for permanent failure in case it is needed. But this is not the case. So I keep my algorithm untouched. I can see two more reasons for us to keep it: 1) It is what we already have in kernel. 2) It is what Windows does (see the disassembly in c35b82ef0294. Original description: Hyper-V TSC page clocksource is suitable for vDSO, however, the protocol defined by the hypervisor is different from VCLOCK_PVCLOCK. Implemented the required support. Simple sysbench test shows the following results: Before: # time sysbench --test=memory --max-requests=500000 run ... real 1m22.618s user 0m50.193s sys 0m32.268s After: # time sysbench --test=memory --max-requests=500000 run ... real 0m47.241s user 0m47.117s sys 0m0.008s Vitaly Kuznetsov (3): x86/hyperv: implement hv_get_tsc_page() x86/hyperv: move TSC reading method to asm/mshyperv.h x86/vdso: Add VCLOCK_HVCLOCK vDSO clock read method arch/x86/entry/vdso/vclock_gettime.c | 24 +++++++++++++++ arch/x86/entry/vdso/vdso-layout.lds.S | 3 +- arch/x86/entry/vdso/vdso2c.c | 3 ++ arch/x86/entry/vdso/vma.c | 7 +++++ arch/x86/hyperv/hv_init.c | 48 +++++++++-------------------- arch/x86/include/asm/clocksource.h | 3 +- arch/x86/include/asm/mshyperv.h | 58 +++++++++++++++++++++++++++++++++++ arch/x86/include/asm/vdso.h | 1 + drivers/hv/Kconfig | 3 ++ 9 files changed, 114 insertions(+), 36 deletions(-) -- 2.9.3 _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
