linux-kernel - Re: [PATCH] slub Discard slab page only when node partials

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Date:	Thu, 29 Sep 2011 09:32:29 -0500 (CDT)
From:	Christoph Lameter <cl@...two.org>
To:	"Alex,Shi" <alex.shi@...el.com>
cc:	Pekka Enberg <penberg@...helsinki.fi>,
	"Chen, Tim C" <tim.c.chen@...el.com>,
	"Huang, Ying" <ying.huang@...el.com>,
	"Huang, Ying" <ying.huang@...el.com>,
	Andi Kleen <ak@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH] slub Discard slab page only when node partials > minimum
 setting

On Thu, 29 Sep 2011, Alex,Shi wrote:

> > Is it really worth it? The higher the value the higher the potential
> > memory that is stuck in the per cpu partial pages?
>
> It is hard to find best balance. :)

Well then lets err on the side of smaller memory use for now.

> I am tested aim9/netperf, both of them was said related to memory
> allocation, but didn't find performance change with/without PCP. Seems
> only hackbench sensitive on this. As to aim9, whichever with ourself
> configuration, or with Mel Gorman's aim9 configuration from his mmtest,
> both of them has no clear performance change for PCP slub.

AIM9 tests are usually single threaded so I would not expect any
differences. Try AIM7? And concurrent netperfs?

The PCP patch helps only if there is node lock contention. Meaning
simultaneous allocations/frees from multiple processor from the same
cache.

> Checking the kernel function call graphic via perf record/perf report,
> slab function only be used much in hackbench benchmark.

Then the question arises if its worthwhile merging if it only affects this
benchmark.

> Above is what I did this week for PCP.
>
> BTW, I will take my one week holiday from tomorrow. e-mail access will
> be slow.

Have a nice holiday.
View attachment "patch-pcpnodump" of type "TEXT/X-PATCH" (3746 bytes)