From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rik van Riel Subject: Re: [RFC 4/7] change kernel accounting to include steal time Date: Thu, 26 Aug 2010 17:19:23 -0400 Message-ID: <4C76DA5B.2030701@redhat.com> References: <1282772597-4183-1-git-send-email-glommer@redhat.com> <1282772597-4183-2-git-send-email-glommer@redhat.com> <1282772597-4183-3-git-send-email-glommer@redhat.com> <1282772597-4183-4-git-send-email-glommer@redhat.com> <1282772597-4183-5-git-send-email-glommer@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, avi@redhat.com, zamsden@redhat.com, mtosatti@redhat.com To: Glauber Costa Return-path: Received: from mx1.redhat.com ([209.132.183.28]:56036 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752690Ab0HZVTZ (ORCPT ); Thu, 26 Aug 2010 17:19:25 -0400 Received: from int-mx02.intmail.prod.int.phx2.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id o7QLJPnh026030 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Thu, 26 Aug 2010 17:19:25 -0400 In-Reply-To: <1282772597-4183-5-git-send-email-glommer@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 08/25/2010 05:43 PM, Glauber Costa wrote: > This patch proposes a common steal time implementation. When no > steal time is accounted, we just add a branch to the current > accounting code, that shouldn't add much overhead. > > When we do want to register steal time, we proceed as following: > - if we would account user or system time in this tick, and there is > out-of-cpu time registered, we skip it altogether, and account steal > time only. > - if we would account user or system time in this tick, and we got the > cpu for the whole slice, we proceed normaly. > - if we are idle in this tick, we flush out-of-cpu time to give it the > chance to update whatever last-measure internal variable it may have. > > This approach is simple, but proved to work well for my test scenarios. > in a UP guest on UP host, with a cpu-hog in both guest and host shows > ~ 50 % steal time. steal time is also accounted proportionally, if > nice values are given to the host cpu-hog. > > A cpu-hog in the host with no load in the guest, produces 0 % steal time, > with 100 % idle, as one would expect. > > Signed-off-by: Glauber Costa > --- > include/linux/sched.h | 1 + > kernel/sched.c | 29 +++++++++++++++++++++++++++++ > 2 files changed, 30 insertions(+), 0 deletions(-) > > diff --git a/include/linux/sched.h b/include/linux/sched.h > index 0478888..e571ddd 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -312,6 +312,7 @@ long io_schedule_timeout(long timeout); > extern void cpu_init (void); > extern void trap_init(void); > extern void update_process_times(int user); > +extern cputime_t (*hypervisor_steal_time)(void); > extern void scheduler_tick(void); > > extern void sched_show_task(struct task_struct *p); > diff --git a/kernel/sched.c b/kernel/sched.c > index f52a880..9695c92 100644 > --- a/kernel/sched.c > +++ b/kernel/sched.c > @@ -3157,6 +3157,16 @@ unsigned long long thread_group_sched_runtime(struct task_struct *p) > return ns; > } > > +cputime_t (*hypervisor_steal_time)(void) = NULL; > + > +static inline cputime_t get_steal_time_from_hypervisor(void) > +{ > + if (!hypervisor_steal_time) > + return 0; > + return hypervisor_steal_time(); > +} > + > + > /* > * Account user cpu time to a process. > * @p: the process that the cpu time gets accounted to > @@ -3169,6 +3179,12 @@ void account_user_time(struct task_struct *p, cputime_t cputime, > struct cpu_usage_stat *cpustat =&kstat_this_cpu.cpustat; > cputime64_t tmp; > > + tmp = get_steal_time_from_hypervisor(); > + if (tmp) { > + account_steal_time(tmp); > + return; > + } > + > /* Add user time to process. */ > p->utime = cputime_add(p->utime, cputime); > p->utimescaled = cputime_add(p->utimescaled, cputime_scaled); I see one problem here. What if get_steal_time_from_hypervisor() returns a smaller amount of time than "cputime"? Would it be better to account tmp as stealtime, and the difference (cputime - tmp) as user/sys/... time? -- All rights reversed