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From Daryl King <allnatives.onl...@gmail.com>
Subject Re: [users@httpd] apache segfault debugging with gdb - need advice
Date Sat, 22 Aug 2015 13:58:39 GMT
I have set my siege concurrency level a bit lower (20 users) and that seems
to have resolved the segfault issue. Its strange that I hadn't read
anywhere else that a lack of resources could cause that, but there it is. I
guess that running Debian 8, Apache 2.4.10, php-fpm and Mariadb was just a
bit too much to ask of my single core 512mb VPS?
On Aug 22, 2015 1:13 PM, "Kurtis Rader" <krader@skepticism.us> wrote:

> On Fri, Aug 21, 2015 at 6:14 PM, Daryl King <allnatives.online@gmail.com>
> wrote:
>
>> Thanks Ryan. Strangely when running "ulimit -n" it returns 65536 in a ssh
>> session, but 1024 in webmin? Which one would be correct?
>>
>
> Limits set by the ulimit command (and the setrlimit syscall) are correct
> if they are high enough to allow a correctly functioning program to perform
> its task. They are incorrect if set too low for the needs of a correctly
> functioning program or so high that a malfunctioning program is able to
> adversely affect the functioning of other processes. So the answer to your
> question is: it depends.
>
> Having said that it is very unusual these days for "ulimit -n" to be set
> too high. Supporting thousands of open files in a single process is
> normally pretty cheap in terms of kernel memory, CPU cycles, etc. So if you
> have a reason to think your program (e.g., httpd) has a legitimate need to
> have more than 1024 files open simultaneously go ahead and increase the
> "ulimit -n" (which is the setrlimit RLIMIT_NOFILE parameter) to a higher
> value.
>
> However, in my experience it is unusual for a too low limit on the number
> of open files to result in a segmentation fault. Especially in a well
> written program like Apache HTTPD. A well written program will normally
> check whether the open (or any syscall which returns a file descriptor)
> failed and refuse to use the -1 value as if it were a valid file descriptor
> number. So I would be surprised if increasing that value resolved the
> segmentation fault.
>
> --
> Kurtis Rader
> Caretaker of the exceptional canines Junior and Hank
>

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