From: Rick James
Date: August 28 2012 4:40pm
Subject: RE: qcache settings and block meaning
List-Archive: http://lists.mysql.com/mysql/228096
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> | Qcache_hits                       | 56418967     |
> | Qcache_inserts                    | 48601636     |
That's a low hit rate.  Perhaps you should simply turn off the Query cache?

> | Qcache_free_memory                | 46945512     |
That's a big fraction of the total.  Either the QC is unnecessarily big, or=
 it was recently purged.

> | Qcache_lowmem_prunes              | 21948806     |
What is Uptime?  This may be a lot of prunes per second.

Purging stuff out of 128MB _may_ slow your system down more than the benefi=
t you are getting.
I recommend turning off the QC for systems with constant write activity.
Otherwise, 50M is a reasonable max.

> -----Original Message-----
> From: raphinou@stripped [mailto:raphinou@stripped] On Behalf Of
> Raphael Bauduin
> Sent: Tuesday, August 28, 2012 7:12 AM
> To: mysql@stripped
> Subject: qcache settings and block meaning
>=20
> Hi,
>=20
> I have a mysql server running with the query cache size being 128M
> (134217728 bytes).
>=20
> Here are the qcache variables values:
>=20
> | Qcache_free_blocks                | 13758        |
> | Qcache_free_memory                | 46945512     |
> | Qcache_hits                       | 56418967     |
> | Qcache_inserts                    | 48601636     |
> | Qcache_lowmem_prunes              | 21948806     |
> | Qcache_not_cached                 | 39066097     |
> | Qcache_queries_in_cache           | 44858        |
> | Qcache_total_blocks               | 104668
>=20
> And the query_cache_min_res_unit is 4096 .
>=20
> I'm not sure what the meaning of a block is. For the query cache size
> and the number of total blocks, I have a block size of
> 134217728/104668 =3D 1282.3186 , which is a strange number for a block
> size. Am I wrong somewhere?
>=20
> Thanks
>=20
> Raph
>=20
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