Messages in this thread | | | Date | Wed, 16 Dec 2015 18:04:28 +0100 | Subject | Re: sched : performance regression 24% between 4.4rc4 and 4.3 kernel | From | Jirka Hladky <> |
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Hi Peter,
you are right the kernel 4.4-rc4 has it already fixed. It seems I will need to redo the bisecting once again, starting with 2a595721a1fa6b684c1c818f379bef834ac3d65e
git bisect start -- kernel/sched git bisect bad v4.4-rc4 git bisect good 2b49d84b259fc18e131026e5d38e7855352f71b9 Bisecting: 32 revisions left to test after this (roughly 5 steps) [da7142e2ed735e1c1bef5a757dc55de35c65fbd6] sched/core: Simplify preempt_count tests
I will let you know the outcome.
Jirka
On Wed, Dec 16, 2015 at 2:50 PM, Peter Zijlstra <peterz@infradead.org> wrote: > On Wed, Dec 16, 2015 at 01:56:17PM +0100, Jirka Hladky wrote: >> Hi Rik, >> >> I have redone the bisecting and have new results: >> >> # first bad commit: [2a595721a1fa6b684c1c818f379bef834ac3d65e] >> sched/numa: Convert sched_numa_balancing to a static_branch >> >> Could you please have a look what went wrong? > > The below is obviously wrong, but your kernel should have that patch. > > So if you revert this patch (ie. go back to the regular variable) it > works again? > > --- > > commit b52da86e0ad58f096710977fcda856fd84da9233 > Author: Srikar Dronamraju <srikar@linux.vnet.ibm.com> > Date: Fri Oct 2 07:48:25 2015 +0530 > > sched/numa: Fix task_tick_fair() from disabling numa_balancing > > If static branch 'sched_numa_balancing' is enabled, it should kickstart > NUMA balancing through task_tick_numa(). However the following commit: > > 2a595721a1fa ("sched/numa: Convert sched_numa_balancing to a static_branch") > > erroneously disables this. > > Fix this anomaly by enabling task_tick_numa() when the static branch > 'sched_numa_balancing' is enabled. > > Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > Cc: Linus Torvalds <torvalds@linux-foundation.org> > Cc: Mel Gorman <mgorman@suse.de> > Cc: Mike Galbraith <efault@gmx.de> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Rik van Riel <riel@redhat.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: linux-kernel@vger.kernel.org > Link: http://lkml.kernel.org/r/1443752305-27413-1-git-send-email-srikar@linux.vnet.ibm.com > Signed-off-by: Ingo Molnar <mingo@kernel.org> > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 4df37a48f499..3bdc3da7bc6a 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -7881,7 +7881,7 @@ static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued) > entity_tick(cfs_rq, se, queued); > } > > - if (!static_branch_unlikely(&sched_numa_balancing)) > + if (static_branch_unlikely(&sched_numa_balancing)) > task_tick_numa(rq, curr); > } >
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