From: Mike Galbraith <umgwanakikbuti@gmail.com>
To: Frederic Weisbecker <fweisbec@gmail.com>, Rik van Riel <riel@redhat.com>
Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de,
mingo@kernel.org, peterz@infradead.org, luto@amacapital.net,
Clark Williams <williams@redhat.com>
Subject: Re: [PATCH 2/2] sched,time: call __acct_update_integrals once a jiffy
Date: Sat, 30 Jan 2016 18:53:05 +0100 [thread overview]
Message-ID: <1454176385.3797.23.camel@gmail.com> (raw)
In-Reply-To: <20160130142037.GA32581@lerouge>
On Sat, 2016-01-30 at 15:20 +0100, Frederic Weisbecker wrote:
> On Fri, Jan 29, 2016 at 05:43:28PM -0500, Rik van Riel wrote:
> > Run times for the microbenchmark:
> >
> > 4.4 3.8 seconds
> > 4.5-rc1 3.7 seconds
> > 4.5-rc1 + first patch 3.3 seconds
> > 4.5-rc1 + both patches 2.3 seconds
>
> Very nice improvement!
Tasty indeed.
When nohz_full CPUs are not isolated, ie are being used as generic
CPUs, get_nohz_timer_target() is a problem with things like tbench.
tbench 8 with Rik's patches applied:
nohz_full=empty
Throughput 3204.69 MB/sec 1.000
nohz_full=1-3,5-7
Throughput 1354.99 MB/sec .422 1.000
nohz_full=1-3,5-7 + club below
Throughput 2762.22 MB/sec .861 2.038
With Rik's patches and a club, tbench becomes nearly acceptable.
---
include/linux/tick.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -184,7 +184,7 @@ static inline const struct cpumask *hous
static inline bool is_housekeeping_cpu(int cpu)
{
#ifdef CONFIG_NO_HZ_FULL
- if (tick_nohz_full_enabled())
+ if (tick_nohz_full_enabled() && runqueue_is_isolated(cpu))
return cpumask_test_cpu(cpu, housekeeping_mask);
#endif
return true;
next prev parent reply other threads:[~2016-01-30 17:53 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-29 22:22 [PATCH 0/2] sched,time: reduce nohz_full syscall overhead 40% riel
2016-01-29 22:22 ` [PATCH 1/2] sched,time: remove pointless divides from __acct_update_integrals riel
2016-01-29 23:10 ` Peter Zijlstra
2016-01-30 3:36 ` Frederic Weisbecker
2016-01-30 3:47 ` Rik van Riel
2016-01-29 22:23 ` [PATCH 2/2] sched,time: call __acct_update_integrals once a jiffy riel
2016-01-29 22:43 ` Rik van Riel
2016-01-30 14:20 ` Frederic Weisbecker
2016-01-30 17:53 ` Mike Galbraith [this message]
2016-01-30 20:36 ` Frederic Weisbecker
2016-01-31 2:52 ` Mike Galbraith
2016-01-31 5:37 ` Mike Galbraith
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