In message prayer.1.3.2.1001241549090@hermes-2.csi.cam.ac.uk, Chris Thomp
son writes:
On Friday, I wrote:
We upgraded our main recursive nameservers (validating, via dlv.isc.org)
from 9.6.1-P2 to 9.6.1-P3 a couple of days ago. CPU (and possibly memory)
consumption have been quite a bit larger since then, and more worryingly,
seems to be gradually increasing.
I have looked for a co-incidental change in the query pattern that might
explain this, without success so far. If anyone else has seen a similar
effect as a result of upgrading, please let me know.
I have found the cause, and it was not the upgrade to 9.6.1-P3 (so apologies
for introducing any FUD about that) or a significant change to the query
load.
It was the result of adding -m record to the named argument list. I had
put this in the startup script for when named was next restarted, and
then half forgotten about it. I had in any case convinced myself that
it was a trivial-cost option. Well, that turns out not to be the case ...
It costs a ~16 bytes per memory allocation to perform the accounting
in a 32 bit build. ~24 bytes in a 64 bit build. Plus some computing
time.
struct debuglink {
ISC_LINK(debuglink_t) link;
const void *ptr[DEBUGLIST_COUNT];
unsigned intsize[DEBUGLIST_COUNT];
const char *file[DEBUGLIST_COUNT];
unsigned intline[DEBUGLIST_COUNT];
unsigned intcount;
};
With this we know where the memory that leaks was allocated and a
starting point to find the defect.
Mark
(Using -m record was motivated by a unfreed-memory-at-shutdown abort
that we observed with 9.6.1-P1 -- and not since -- and reported on
bind9-bugs as RT #20675.)
--
Chris Thompson
Email: c...@cam.ac.uk
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--
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742 INTERNET: ma...@isc.org
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