Since shm (shared memory) in Unix/Linux is only used to share memory between independent processes and mysql server is a single process (multi-threaded), I am convinced that shmmax value has no consequence on mysql. (OTOH Oracle has a multiprocess architecture and uses shared memory).
Hope this helps, Joseph Bueno
Philipp wrote:
Dear Walt, dear List,
thank you for your reply. Finally a suggestions at all. I checked both
/proc/sys/kernel/threads-max /proc/sys/kernel/shmmax
I dont think threads-max will be a problem, because the value is 14336, and i dont think my system will ever have to handle this number of threads.
But researching shmmax at google i got several hits. Most are dealing with postgres but perhaps its the same with mysql.
shmmax ist 32 MB. on one page the author suggest to raise this value to 128 MB.
What are your suggestions for the values:
shmall shmmax shmmni ?
Thank you very much, Yours Philipp
----- Original Message ----- From: "walt" <[EMAIL PROTECTED]> To: "Philipp" <[EMAIL PROTECTED]> Cc: <[EMAIL PROTECTED]> Sent: Monday, March 17, 2003 6:48 PM Subject: Re: Process Limit on Linux ?
Philipp wrote:
Hi there,
i wrote several times to the list asking for help with a problem regarding process limits on linux, but never got an answer. today i found this story:
http://www.mysql.com/press/user_stories/handy.de.html
here are the relevant sentences:
"We had some process limit problems on our Linux Systems, but thanks to your support we where able to patch the linux boxes and move the limit to a size that meets our needs (we've got an average
of
about 1600 concurrent threads per server)."
These people use 2.2 Kernels so i dont know if the mentioned kernel and glibc patching is also relevant for me, as i am using 2.4 kernels only.
Here is my problem in detail:
i am using mysql-3.23.55 binary packages on linux 2.4.20 and i raised
ulimit
values and configuration in my.conf to allow more then 1500 threads. but when there are around 750 threads a new client connecting is told something
like
that (dont have the errno at the moment, i think its 11):
"cant create new thread, perhaps you are out of memory or there is a os-depended bug".
The machine only runs apache and mysql and is a Xeon 2x2 2.4 Gz with 2
GB of
RAM. cat /proc/meminfo sais that more then 1 Gig is used for caching, so
memory
should be no problem .
Please, if you have any ideas, let me know. If it is a kernel issue,
tell me
to go to linux mailing lists or if its some kind of "secret issue" only the support will be able to answer let me know that.
Thanks in advance, Philipp
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Philipp, Did you check /proc/sys/kernel/threads-max? I know with oracle 8i, you are supposed to increase /proc/sys/kernel/shmmax as well as some other values. You might check into that and see if changing those values will help. Does your syslog say anything when these problems occur?
walt
walt
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