Bug #35160 for bind9-public: freelists in memory context consume memory indefinitely

Hello, I would like to ask you about details of memory context behavior in BIND 9.9.3-P2, some details seems weird to me. May be that it is a bug or I just misunderstood something ... Thank you very much for your time! I think that small memory blocks which are referenced by "struct isc__mem->freelists" are never freed (I mean returned to the operating system) until the memory context is destroyed, right? I'm attaching small demonstration program which does this: 0) create() empty memory context 1) get() 1 million of 1 KiB blocks 2) put() all the blocks back to the mctx 3) destroy() mctx The program pauses after each step which allows to investigate memory consumption as seen by the operating system. I compile it with: gcc -std=c99 -ldns -lisc -I/usr/include/bind9 -g -O0 -o mctx mctx.c I understand that freelists mechanism saves overhead of the operating system allocator for small blocks, but I'm missing a way how to 'flush' freelists. Use case: I'm developing a database driver for BIND 9 and I'm in situation when the driver does a lot of small allocations during zone loading. My problem is that after initial processing the driver "puts" most of the small blocks back to the mctx but this memory is not returned back to the operating system. I'm not sure if this problem deserves own function for explicit 'freelists flush', but generally I could use that in my code. May be that solution like "automatically flush freelists if ((total - inuse) > inuse)" would be good enough and even the plain BIND could benefit from that. May be that factor 2 is too big, may be that and 1/2 would be more appropriate ... if ((total - inuse) > (inuse >> 1)) Could you recommend something else to me if the approaches mentioned above are not feasible? Thank you very much for your patience with me :-) -- Petr Spacek Red Hat

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