linux-kernel - Re: [RT LATENCY] 249 microsecond latency caused by slub's unfreeze

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Date:	Fri, 22 Mar 2013 23:51:13 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Christoph Lameter <cl@...ux.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	RT <linux-rt-users@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Clark Williams <clark@...hat.com>
Subject: Re: [RT LATENCY] 249 microsecond latency caused by slub's
 unfreeze_partials() code.

On Fri, 2013-03-22 at 15:41 +0000, Christoph Lameter wrote:

> The control is via the cpu_partial field in /sys/kernel/slab/<cache>/
> 
> There is also slabs_cpu_partial which gives a view as to how many objects
> are cached in each per cpu structure. Do a cat
> 
> /sys/kernel/*/slabs_cpu_partial to get a view of what the situation is.
> Any abnormally high numbers?
> 
> The default for the number of per cpu partial objects should be 30 or so.

I just triggered another latency:

hackbenc-31634   5d..31 103261.991668: sched_switch:         hackbench:31634 [120] D ==> hackbench:36093 [120]
hackbenc-36093   5d...0 103261.991670: funcgraph_entry:      ! 225.665 us |  unfreeze_partials();
hackbenc-36093   5d...0 103261.991897: funcgraph_entry:                   |  smp_apic_timer_interrupt() {
hackbenc-36093   5d.h10 103261.991897: hrtimer_expire_entry: hrtimer=0xffff881f5ca7fe88 now=103293011955940 function=hrtimer_wakeup/0x0
hackbenc-36093   5d.h30 103261.991898: sched_wakeup:         cyclictest:8946 [4] success=1 CPU:005
hackbenc-36093   5dN..0 103261.991901: funcgraph_exit:         3.589 us   |  }
hackbenc-36093   5d..30 103261.991902: sched_switch:         hackbench:36093 [120] R ==> cyclictest:8946 [4]

I did a: cat /sys/kernel/slab/*/slabs_cpu_partial > slab_partials

I uploaded it here:

http://rostedt.homelinux.com/private/slab_partials

See anything I should be worried about?

Thanks,

-- Steve



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