From: Eric Bergen
Date: May 29 2009 9:59pm
Subject: Re: Why can't I kill the query cache?
List-Archive: http://lists.mysql.com/mysql/217741
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You can also flush the cache with echo 1 > /proc/sys/vm/drop_caches if
you have a new enough kernel.

On Fri, May 29, 2009 at 2:16 PM, Dan Nelson <dnelson@stripped> wrote=
:
> In the last episode (May 29), Gerald L. Clark said:
>> Little, Timothy wrote:
>> > Also titled, I want this to run slow ALL the time...
>> >
>> > I have a group of dreadful queries that I have to optimize.
>> >
>> > Some take 20-30 seconds each -- the first time that I run them. =A0But
>> > then they never seem to take that long after the first time (taking le=
ss
>> > than a second then). =A0If I change the "keywords" searched for in the
>> > where clauses, then they take a long time again... =A0so it's the
>> > query-cache or something just like it.
>> >
>> > BUT, I am doing this each time :
>> > flush tables;
>> > reset query cache;
>> > set global query_cache_size=3D0;
>> > SELECT =A0 SQL_NO_CACHE DISTINCT ca.conceptid AS headingid,
>> >
>> > And still it's not avoiding the cache.
>> >
>> > Is there a cache I'm missing?
>> >
>> > Tim...
>> >
>> >
>> Disk cache, but I don't know how to clear it.
>
> Create a file 2x the size of your RAM (for a 2gb system, dd if=3D/dev/zer=
o
> of=3Dbigfile bs=3D1024k count=3D4096), then dd it to /dev/null (dd if=3Db=
igfile
> of=3D/dev/null bs=3D1024k). =A0That should flush your OS cache. =A0The gu=
aranteed
> way would be to dismount then remount your filesystem, but that could be
> difficult depending on how many other processes are using it..
>
> --
> =A0 =A0 =A0 =A0Dan Nelson
> =A0 =A0 =A0 =A0dnelson@stripped
>
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>
>



--=20
Eric Bergen
eric.bergen@stripped
http://www.ebergen.net