From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932294AbaGQK7L (ORCPT ); Thu, 17 Jul 2014 06:59:11 -0400 Received: from mail-we0-f170.google.com ([74.125.82.170]:34894 "EHLO mail-we0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932251AbaGQK7H (ORCPT ); Thu, 17 Jul 2014 06:59:07 -0400 Message-ID: <53C7AC71.3090902@redhat.com> Date: Thu, 17 Jul 2014 12:58:57 +0200 From: Paolo Bonzini User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Thomas Gleixner , LKML CC: John Stultz , Peter Zijlstra , Gleb Natapov , kvm@vger.kernel.org Subject: Re: [patch V2 44/64] x86: kvm: Make kvm_get_time_and_clockread() nanoseconds based References: <20140716205018.175419210@linutronix.de> <20140716205055.929964640@linutronix.de> In-Reply-To: <20140716205055.929964640@linutronix.de> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Il 16/07/2014 23:04, Thomas Gleixner ha scritto: > Convert the relevant base data right away to nanoseconds instead of > doing the conversion on every readout. Reduces text size by 160 bytes. > > Signed-off-by: Thomas Gleixner > Cc: Gleb Natapov > Cc: kvm@vger.kernel.org > --- > arch/x86/kvm/x86.c | 44 ++++++++++++++------------------------------ > 1 file changed, 14 insertions(+), 30 deletions(-) > > Index: tip/arch/x86/kvm/x86.c > =================================================================== > --- tip.orig/arch/x86/kvm/x86.c > +++ tip/arch/x86/kvm/x86.c > @@ -984,9 +984,8 @@ struct pvclock_gtod_data { > u32 shift; > } clock; > > - /* open coded 'struct timespec' */ > - u64 monotonic_time_snsec; > - time_t monotonic_time_sec; > + u64 boot_ns; > + u64 nsec_base; > }; > > static struct pvclock_gtod_data pvclock_gtod_data; > @@ -994,6 +993,9 @@ static struct pvclock_gtod_data pvclock_ > static void update_pvclock_gtod(struct timekeeper *tk) > { > struct pvclock_gtod_data *vdata = &pvclock_gtod_data; > + u64 boot_ns; > + > + boot_ns = ktime_to_ns(ktime_add(tk->base_mono, tk->offs_boot)); > > write_seqcount_begin(&vdata->seq); > > @@ -1004,17 +1006,8 @@ static void update_pvclock_gtod(struct t > vdata->clock.mult = tk->mult; > vdata->clock.shift = tk->shift; > > - vdata->monotonic_time_sec = tk->xtime_sec > - + tk->wall_to_monotonic.tv_sec; > - vdata->monotonic_time_snsec = tk->xtime_nsec > - + (tk->wall_to_monotonic.tv_nsec > - << tk->shift); > - while (vdata->monotonic_time_snsec >= > - (((u64)NSEC_PER_SEC) << tk->shift)) { > - vdata->monotonic_time_snsec -= > - ((u64)NSEC_PER_SEC) << tk->shift; > - vdata->monotonic_time_sec++; > - } > + vdata->boot_ns = boot_ns; > + vdata->nsec_base = tk->xtime_nsec; > > write_seqcount_end(&vdata->seq); > } > @@ -1371,23 +1364,22 @@ static inline u64 vgettsc(cycle_t *cycle > return v * gtod->clock.mult; > } > > -static int do_monotonic(struct timespec *ts, cycle_t *cycle_now) > +static int do_monotonic_boot(s64 *t, cycle_t *cycle_now) > { > + struct pvclock_gtod_data *gtod = &pvclock_gtod_data; > unsigned long seq; > - u64 ns; > int mode; > - struct pvclock_gtod_data *gtod = &pvclock_gtod_data; > + u64 ns; > > - ts->tv_nsec = 0; > do { > seq = read_seqcount_begin(>od->seq); > mode = gtod->clock.vclock_mode; > - ts->tv_sec = gtod->monotonic_time_sec; > - ns = gtod->monotonic_time_snsec; > + ns = gtod->nsec_base; > ns += vgettsc(cycle_now); > ns >>= gtod->clock.shift; > + ns += gtod->boot_ns; > } while (unlikely(read_seqcount_retry(>od->seq, seq))); > - timespec_add_ns(ts, ns); > + *t = ns; > > return mode; > } > @@ -1395,19 +1387,11 @@ static int do_monotonic(struct timespec > /* returns true if host is using tsc clocksource */ > static bool kvm_get_time_and_clockread(s64 *kernel_ns, cycle_t *cycle_now) > { > - struct timespec ts; > - > /* checked again under seqlock below */ > if (pvclock_gtod_data.clock.vclock_mode != VCLOCK_TSC) > return false; > > - if (do_monotonic(&ts, cycle_now) != VCLOCK_TSC) > - return false; > - > - monotonic_to_bootbased(&ts); > - *kernel_ns = timespec_to_ns(&ts); > - > - return true; > + return do_monotonic_boot(kernel_ns, cycle_now) == VCLOCK_TSC; > } > #endif > > > Acked-by: Paolo Bonzini