Hi,
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" <kernel@stripped>
> To: "Philipp" <kernel@stripped>
> Cc: <mysql@stripped>
> 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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>
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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
>>
>
