[ZODB-Dev] BerkeleyDB's page cache

[Toby Dickenson]

On Mon, 17 Dec 2001 14:32:42 +0000, Chris Withers <chrisw@nipltd.com>
wrote:

>Toby Dickenson wrote:
>>=20
>> * Storage choice had little impact on overall system throughput
>> Specifically, I didnt see the performance problems that Chris W =
reported
>> (although my databases are somewhat smaller).
>
>Yeah, I think what was happening here is that BerkleyStorage was chewign=
 up RAM,
>causing the sytem to thrash, hence the poor performance...

If we exclude packing, my evidence is the opposite of the that.
BerkeleyStorage/Full had a flat memory usage profile during normal
use, which is what I expect from looking at the code.

Chris, did you add a set_cachesize line in your DB_CONFIG file? That
controls the size of BerkeleyDB's internal cache. Running with the
default of 256k could well cause thashing in that cache. If you still
have your database environment around, "db_stat -m" will tell you
"number of pages found in cache". The number is application-dependant
(as always) but I guess anything below 95% is a sign of trouble.



Toby Dickenson
tdickenson@geminidataloggers.com