dccd memory usage

Richard Underwood richard@aspectgroup.co.uk
Mon Oct 4 11:10:52 UTC 2004


Hi,

	I'm curious about the memory usage of dccd. Three times now since
starting to run dccd, I've had problems with the server dying. From what
info I've been able to recover, I believe this is due to memory exhaustion
of some sort.

	I'm not by any means blaming this on dccd, but it does form part of
the bigger picture.

	I've been graphing the memory usage of the dccd process which can be
seen here:

http://lurgy.aspect-internet.com/explode_dccdmem-month.png

	The green area is the VSZ (virtual size) output from ps, and the
blue line is the RSS (resident size) from ps. As you can see, the virtual
size has been growing steadily (and peaked at 1541M. The resident size is
pretty costant, rising and falling with what I assume are daily database
cleans.

	Looking at the logs, it says:

Oct  4 09:50:41 explode dccd[2145]: 1.2.54 listening to port 6277 with
/var/dcc and 1501 MByte window

	... this 1501 tying up with what I'm seeing. Judging from the maps
it has (currently 42 to dcc_db.hash and 82 to dcc_db), which grow in
proportion to the memory.

	I'm guessing that this is designed to speed up the hash file access
by exchanging memory for cpu/IO performance. However, 800M/1501M is quite a
chunk on a machine with 2G, particularly as, during normal operation, the
CPU usage is negligible.

	Is there any way to tune this figure? Or have I missed the point
completely?

	Thanks,

		Richard



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