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 <dnel...@allantgroup.com> 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 > dnel...@allantgroup.com > > -- > MySQL General Mailing List > For list archives: http://lists.mysql.com/mysql > To unsubscribe: http://lists.mysql.com/mysql?unsub=eric.ber...@gmail.com > > -- Eric Bergen eric.ber...@gmail.com http://www.ebergen.net -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/mysql?unsub=arch...@jab.org
