search for: vread_hvclock

On Thu, 9 Feb 2017, Vitaly Kuznetsov wrote: > +#ifdef CONFIG_HYPERV_TSCPAGE > +static notrace u64 vread_hvclock(int *mode) > +{ > + const struct ms_hyperv_tsc_page *tsc_pg = > + (const struct ms_hyperv_tsc_page *)&hvclock_page; > + u64 sequence, scale, offset, current_tick, cur_tsc; > + > + while (1) { > + sequence = READ_ONCE(tsc_pg->tsc_sequence); > + if (!sequence) > +...

On Thu, 9 Feb 2017, Vitaly Kuznetsov wrote: > +#ifdef CONFIG_HYPERV_TSCPAGE > +static notrace u64 vread_hvclock(int *mode) > +{ > + const struct ms_hyperv_tsc_page *tsc_pg = > + (const struct ms_hyperv_tsc_page *)&hvclock_page; > + u64 sequence, scale, offset, current_tick, cur_tsc; > + > + while (1) { > + sequence = READ_ONCE(tsc_pg->tsc_sequence); > + if (!sequence) > +...

...ly(!(pvti->flags & PVCLOCK_TSC_STABLE_BIT))) + return U64_MAX; ret = __pvclock_read_cycles(pvti, rdtsc_ordered()); } while (pvclock_read_retry(pvti, version)); @@ -148,17 +121,12 @@ static notrace u64 vread_pvclock(int *mo } #endif #ifdef CONFIG_HYPERV_TSCPAGE -static notrace u64 vread_hvclock(int *mode) +static notrace u64 vread_hvclock(void) { const struct ms_hyperv_tsc_page *tsc_pg = (const struct ms_hyperv_tsc_page *)&hvclock_page; - u64 current_tick = hv_read_tsc_page(tsc_pg); - - if (current_tick != U64_MAX) - return current_tick; - *mode = VCLOCK_NONE; - return 0; + r...

Hi, Hyper-V TSC page clocksource is suitable for vDSO, however, the protocol defined by the hypervisor is different from VCLOCK_PVCLOCK. I implemented the required support re-using pvclock_page VVAR. 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

Hi, Hyper-V TSC page clocksource is suitable for vDSO, however, the protocol defined by the hypervisor is different from VCLOCK_PVCLOCK. I implemented the required support re-using pvclock_page VVAR. 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

...lo, b_hi, p1, p2; + + a_lo = (u32)a; + a_hi = a >> 32; + b_lo = (u32)b; + b_hi = b >> 32; + p1 = a_lo * b_hi; + p2 = a_hi * b_lo; + + return a_hi * b_hi + (p1 >> 32) + (p2 >> 32) + + ((((a_lo * b_lo) >> 32) + (u32)p1 + (u32)p2) >> 32); + +} + +static notrace u64 vread_hvclock(int *mode) +{ + const struct ms_hyperv_tsc_page *tsc_pg = + (const struct ms_hyperv_tsc_page *)&pvclock_page; + u64 sequence, scale, offset, current_tick, cur_tsc; + + while (1) { + sequence = READ_ONCE(tsc_pg->tsc_sequence); + if (!sequence) + break; + + scale = READ_ONCE(tsc_pg->t...

...__attribute__((visibility("hidden"))); +#endif + #ifndef BUILD_VDSO32 notrace static long vdso_fallback_gettime(long clock, struct timespec *ts) @@ -141,6 +147,32 @@ static notrace u64 vread_pvclock(int *mode) return last; } #endif +#ifdef CONFIG_HYPERV_TSCPAGE +static notrace u64 vread_hvclock(int *mode) +{ + const struct ms_hyperv_tsc_page *tsc_pg = + (const struct ms_hyperv_tsc_page *)&hvclock_page; + u64 sequence, scale, offset, current_tick, cur_tsc; + + while (1) { + sequence = READ_ONCE(tsc_pg->tsc_sequence); + if (!sequence) + break; + + scale = READ_ONCE(tsc_pg->t...

...> +} Unless GCC is waaay more clever than I think, this is hugely suboptimal on 64-bit. x86 can do this in a single instruction, and gcc can express it cleanly using __uint128_t. I wouldn't be terribly surprised if the 32-bit generated code was fine, too. > + > +static notrace u64 vread_hvclock(int *mode) > +{ > + const struct ms_hyperv_tsc_page *tsc_pg = > + (const struct ms_hyperv_tsc_page *)&pvclock_page; > + u64 sequence, scale, offset, current_tick, cur_tsc; > + > + while (1) { > + sequence = READ_ONCE(tsc_pg->...

...> +} Unless GCC is waaay more clever than I think, this is hugely suboptimal on 64-bit. x86 can do this in a single instruction, and gcc can express it cleanly using __uint128_t. I wouldn't be terribly surprised if the 32-bit generated code was fine, too. > + > +static notrace u64 vread_hvclock(int *mode) > +{ > + const struct ms_hyperv_tsc_page *tsc_pg = > + (const struct ms_hyperv_tsc_page *)&pvclock_page; > + u64 sequence, scale, offset, current_tick, cur_tsc; > + > + while (1) { > + sequence = READ_ONCE(tsc_pg->...

Thomas Gleixner <tglx at linutronix.de> writes: > On Thu, 9 Feb 2017, Vitaly Kuznetsov wrote: >> +#ifdef CONFIG_HYPERV_TSCPAGE >> +static notrace u64 vread_hvclock(int *mode) >> +{ >> + const struct ms_hyperv_tsc_page *tsc_pg = >> + (const struct ms_hyperv_tsc_page *)&hvclock_page; >> + u64 sequence, scale, offset, current_tick, cur_tsc; >> + >> + while (1) { >> + sequence = READ_ONCE(tsc_pg->tsc_sequence); &...

...xdriverproject.org; virtualization at lists.linux-foundation.org >> Subject: Re: [PATCH 2/2] x86/vdso: Add VCLOCK_HVCLOCK vDSO clock read >> method >> >> On Thu, 9 Feb 2017, Vitaly Kuznetsov wrote: >> > +#ifdef CONFIG_HYPERV_TSCPAGE >> > +static notrace u64 vread_hvclock(int *mode) >> > +{ >> > + const struct ms_hyperv_tsc_page *tsc_pg = >> > + (const struct ms_hyperv_tsc_page *)&hvclock_page; >> > + u64 sequence, scale, offset, current_tick, cur_tsc; >> > + >> > + while (1) { >> > +...

...xdriverproject.org; virtualization at lists.linux-foundation.org >> Subject: Re: [PATCH 2/2] x86/vdso: Add VCLOCK_HVCLOCK vDSO clock read >> method >> >> On Thu, 9 Feb 2017, Vitaly Kuznetsov wrote: >> > +#ifdef CONFIG_HYPERV_TSCPAGE >> > +static notrace u64 vread_hvclock(int *mode) >> > +{ >> > + const struct ms_hyperv_tsc_page *tsc_pg = >> > + (const struct ms_hyperv_tsc_page *)&hvclock_page; >> > + u64 sequence, scale, offset, current_tick, cur_tsc; >> > + >> > + while (1) { >> > +...

Hi, 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

Hi, 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

Matt attempted to add CLOCK_TAI support to the VDSO clock_gettime() implementation, which extended the clockid switch case and added yet another slightly different copy of the same code. Especially the extended switch case is problematic as the compiler tends to generate a jump table which then requires to use retpolines. If jump tables are disabled it adds yet another conditional to the existing

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.

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.

Hi, while we're still waiting for a definitive ACK from Microsoft that the algorithm is good for SMP case (as we can't prevent the code in vdso from migrating between CPUs) I'd like to send v2 with some modifications to keep the discussion going. Changes since v1: - Document the TSC page reading protocol [Thomas Gleixner]. - Separate the TSC page reading code from

Hi, while we're still waiting for a definitive ACK from Microsoft that the algorithm is good for SMP case (as we can't prevent the code in vdso from migrating between CPUs) I'd like to send v2 with some modifications to keep the discussion going. Changes since v1: - Document the TSC page reading protocol [Thomas Gleixner]. - Separate the TSC page reading code from

...org; > devel at linuxdriverproject.org; virtualization at lists.linux-foundation.org > Subject: Re: [PATCH 2/2] x86/vdso: Add VCLOCK_HVCLOCK vDSO clock read > method > > On Thu, 9 Feb 2017, Vitaly Kuznetsov wrote: > > +#ifdef CONFIG_HYPERV_TSCPAGE > > +static notrace u64 vread_hvclock(int *mode) > > +{ > > + const struct ms_hyperv_tsc_page *tsc_pg = > > + (const struct ms_hyperv_tsc_page *)&hvclock_page; > > + u64 sequence, scale, offset, current_tick, cur_tsc; > > + > > + while (1) { > > + sequence = READ_ONCE(tsc_pg->tsc_seque...