Hello Michal,

2012/3/5 Michal Trojnara Michal.Trojnara@mirt.net

I am using fork mode because of leaks with pthread. In 4.33+pthread,

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stunnel virt size (per top) went up to 216m after 40k transactions. In fork mode, stunnel size after the same test was 20744 (kilobytes). In 4.45, I have 187m and 20676k respectively.

I observed the same symptoms. Stunnel grows to ~200MB of virtual memory after some time of usage. Then it stops growing further. I guess this issue is caused by heap fragmentation rather than a memory leak. Otherwise the growth would not be limited to ~200MB. https://en.wikipedia.org/wiki/**C_dynamic_memory_allocationhttps://en.wikipedia.org/wiki/C_dynamic_memory_allocation

I ran a test overnight that confirmed your point. I generated 480k+ stunnel transactions. This morning, stunnel memory usage is virt=187m and res=42m. My result after 40k transactions was exactly the same (in both cases with pthread+zlib).

I understand that virt includes shared libs, and that any issue with a

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shared lib will impact virt size. I did not have the opportunity to test without zlib support in openssl. Since we are not using compression, I wonder how much avoiding zlib would help.

zlib only uses lots of memory when it's enabled.

I ran another test to clarify this. zlib appears to be adding around 3 megabytes at most. This is at least what I see under my setup and type of usage.

pthread+zlib, 40k transactions before: virt=20680, res=792 after: virt=187m, res=42m

pthread+nozlib, 40k transactions before: virt=20688, res=896 after: virt=185m, res=39m

I have seen no benefit of compiling without zlib in fork mode. I guess it only makes forking a bit lighter.

2012/3/5 Michal Trojnara Michal.Trojnara@mirt.net

You may also try to set a lower value of MMAP_THRESHOLD to reduce heap fragmentation: https://www.kernel.org/doc/man-pages/online/pages/man3/malloc.3.html

This will be worth a look. Knowing what is influencing stunnel size is nice since it can avoid us restarting the processes once in a while (which we currently never do in fork mode).

Thanks for your great help!