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Date: Fri, 9 May 2008 21:22:40 +0530 From: Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com> To: "Zhang, Yanmin" <yanmin_zhang@...ux.intel.com> Cc: Dhaval Giani <dhaval@...ux.vnet.ibm.com>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>, Aneesh Kumar KV <aneesh.kumar@...ux.vnet.ibm.com> Subject: Re: volanoMark regression with kernel 2.6.26-rc1 On Thu, May 08, 2008 at 11:41:25AM +0530, Srivatsa Vaddagiri wrote: > The other combination that I am interested to know is when: > > CONFIG_FAIR_GROUP_SCHED=y and CONFIG_CGROUP_SCHED=y > > [i.e cgroup based scheduling rather than uid based scheduling. Former > should result in only one group at bootup] > > I will also try to get some numbers with this combination. I ran with that combination and here are some results: 2.6.25 (with CONFIG_USER_SCHED) Volanomark perf = 20436.6 (Avg of 10 runs) 2.6.26-rc1 + patches in Ingo's tree [1] as of Fri morning IST (abt 8 hrs before) (with CONFIG_CGROUP_SCHED) Volanomark perf = 21529.6 i.e CGROUP based grouping in 2.6.26-rc1 gives same (if not somewhat better) results as UID-based scheduling in 2.6.25. Yamin, Could you validate this as well? i.e just turn on cgroup-based grouping (CONFIG_CGROUP_SCHED) and check the resulting performance with 2625 you already have (using CONFIG_USER_SCHED). A) In 2.6.25, with UID based scheduling, CPU load = summation of task load B) In 2.6.26-rc1, with UID based scheduling, CPU load = summation of group weights C) In 2.6.26-rc1, with CGROUP based scheduling, CPU load = summation of task weights This change in definition of cpu load is affecting load balance routines (find_busiest_group et al). As a result, threads of volanomark benchmark aren't quickly spread across the cpus, resulting in slower performance. In case of B), cpu load can be low numbers (100 or 200), while in A or C, cpu load are large numbers. I think find_busiest_group() and related routines need to be "educated" to deal with such low numbers .. -- Regards, vatsa -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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