Date: Wed, 22 May 2013 20:04:07 +0200 From: "Michael Ross" <gmx@ross.cx> To: "FreeBSD Questions" <freebsd-questions@freebsd.org>, "Alejandro Imass" <aimass@yabarana.com> Subject: Re: MySQL hangs server completely Message-ID: <op.wxhy45zgg7njmm@michael-think> In-Reply-To: <CAHieY7R6Xz=p-6RHN0rKyJaOLBufRv4tNR_XTW3T3Q=bShFGow@mail.gmail.com> References: <CAHieY7R6Xz=p-6RHN0rKyJaOLBufRv4tNR_XTW3T3Q=bShFGow@mail.gmail.com>
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On Wed, 22 May 2013 15:52:45 +0200, Alejandro Imass <aimass@yabarana.com> wrote: > Hi, > > We've been having this problem with a customer for a while and it > seems that some funky query makes MySQL use 100% of CPU. Nevertheless, > even though you can see in top that it's only 1 CPU in 100% (out of 8) > the server eventually becomes useless and stops responding completely. > > So my question is, how does a user process hang the whole server? What > system resources could MySQL be draining to make the server stop > responding completely? > In laymans terms - can't do better - MySQL racing itself to obtain a ( table | memory | file ) lock? I know I can death-stall the MySQL server at a customer's site if I give it a big enough query ( like, DROPping a table, recreating it and pushing backup data inside ) while cron's hourly backup-dump is running on the database. Just the MySQL server, the machine itself hasn't stalled yet - but I'm sitting at the console while doing this, so I don't know what would eventually happen if I'd let it sit for a while. Regards, Michael
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