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. But
>> > then they never seem to take that long after the first time (taking less
>> > than a second then). If I change the "keywords" searched for in the
>> > where clauses, then they take a long time again... so 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=0;
>> > SELECT 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=/dev/zero
> of=bigfile bs=1024k count=4096), then dd it to /dev/null (dd if=bigfile
> of=/dev/null bs=1024k). That should flush your OS cache. The guaranteed
> way would be to dismount then remount your filesystem, but that could be
> difficult depending on how many other processes are using it..
> Dan Nelson
> MySQL General Mailing List
> For list archives: http://lists.mysql.com/mysql
> To unsubscribe: http://lists.mysql.com/mysql?unsub=1