[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <Pine.LNX.4.64.0803171027450.7359@schroedinger.engr.sgi.com>
Date: Mon, 17 Mar 2008 10:32:15 -0700 (PDT)
From: Christoph Lameter <clameter@....com>
To: "Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
cc: Andrew Morton <akpm@...ux-foundation.org>,
Kay Sievers <kay.sievers@...y.org>,
Greg Kroah-Hartman <gregkh@...e.de>,
LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>
Subject: Re: hackbench regression since 2.6.25-rc
On Mon, 17 Mar 2008, Zhang, Yanmin wrote:
> slub_min_objects | 8 | 16 | 32 | 64
> --------------------------------------------------------------------------------------------
> slab(__slab_alloc+__slab_free+add_partial) cpu utilization | 88.00% | 44.00% | 13.00% | 12%
>
>
> When slub_min_objects=32, we could get a reasonable value. Beyond 32, the improvement
> is very small. 32 is just possible_cpu_number*2 on my tigerton.
Interesting. What is the optimal configuration for your 8p? Could you
figure out the optimal configuration for an 4p and a 2p configuration?
> It's hard to say hackbench simulates real applications closely. But it discloses a possible
> performance bottlebeck. Last year, we once captured the kmalloc-2048 issue by tbench. So the
> default slub_min_objects need to be revised. In the other hand, slab is allocated by alloc_page
> when its size is equal to or more than a half page, so enlarging slub_min_objects won't create
> too many slab page buffers.
>
> As for NUMA, perhaps we could define slub_min_objects to 2*max_cpu_number_per_node.
Well for a 4k cpu configu this would set min_objects to 8192. So I think
we could implement a form of logarithmic scaling based on cpu
counts comparable to what is done for the statistics update in vmstat.c
fls(num_online_cpus()) = 4
So maybe
slub_min_objects= 8 + (2 + fls(num_online_cpus())) * 4
--
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/
Powered by blists - more mailing lists