BIND 9.6.1-P3 using more resources?

[Mark Andrews]

In message <Prayer.1.3.2.1001241549090.354 at 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 int            size[DEBUGLIST_COUNT];
        const char             *file[DEBUGLIST_COUNT];
        unsigned int            line[DEBUGLIST_COUNT];
        unsigned int            count;
};

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: cet1 at cam.ac.uk
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-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org