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Date: Mon, 12 Mar 2007 17:00:42 -0500
From: Anton Blanchard <anton@samba.org>
To: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Rik van Riel <riel@redhat.com>, Lorenzo Allegrucci <l_allegrucci@yahoo.it>,
       linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
       Suparna Bhattacharya <suparna@in.ibm.com>,
       Jens Axboe <jens.axboe@oracle.com>
Subject: Re: SMP performance degradation with sysbench
Message-ID: <20070312220042.GA807@kryten>
References: <1172425476.5489.11.camel@odyssey.lan> <45E21FEC.9060605@redhat.com> <45E2E244.8040009@yahoo.com.au>
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Hi Nick,

> Anyway, I'll keep experimenting. If anyone from MySQL wants to help look
> at this, send me a mail (eg. especially with the sched_setscheduler issue,
> you might be able to do something better).

I took a look at this today and figured Id document it:

http://ozlabs.org/~anton/linux/sysbench/

Bottom line: it looks like issues in the glibc malloc library, replacing
it with the google malloc library fixes the negative scaling:

# apt-get install libgoogle-perftools0
# LD_PRELOAD=/usr/lib/libtcmalloc.so /usr/sbin/mysqld

Anton