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From Sylvain Goulmy <sygou...@gmail.com>
Subject Re: [users@httpd] Apache 2.4 create a huge amount of shared memory segments
Date Fri, 19 Dec 2014 10:07:25 GMT
I also forgot to mention that i have set the BalancerInherit to Off before
loading the balancers definition. It unfortunatly doesn't change the
behaviour.

Sylvain

On Fri, Dec 19, 2014 at 11:04 AM, Sylvain Goulmy <sygoulmy@gmail.com> wrote:
>
> Hi Yann,
>
> Thank you for your feedback.
>
> My configuration is currently defining 338 virtual hosts and 169 proxy
> balancers.
>
> The balancers are defined in the main section. Each virtual host refers
> only one balancer.
>
> Here what i notice :
> - Apache creates one shm for each balancer
> - Each virtual hosts creates one shm for each balancer even if it doesn't
> refer it...
>
> Am i missing a directive that could avoid that behaviour or do i have to
> redesign my all configuration by moving each balancer definition at the
> virtual host level ?
>
> Thanks in advance.
> Regards.
>
> Sylvain
>
>
> On Fri, Dec 19, 2014 at 12:06 AM, Yann Ylavic <ylavic.dev@gmail.com>
> wrote:
>
>> If you can manage to recompile the APR library used by your Apache 2.4
>> (you probably did that already since 2.4 does not seem to be the
>> version packaged with RHEL 6.4), you can use "./configure
>> --enable-posix-shm ..." to use another shared memory mechanism than
>> the default one (IPC SysV) which is limited to 32K segments (system
>> wide).
>> The number of segments would then be limited by the usual number of
>> file descriptors per process (ulimit -n).
>>
>> Unfortunately, there no equivalent to the Mutex directive for shared
>> memories, this can't be changed by httpd's configuration (as far as I
>> know).
>>
>> On Thu, Dec 18, 2014 at 2:30 PM, Sylvain Goulmy <sygoulmy@gmail.com>
>> wrote:
>> >
>> > I also noticed that a single proxy_balancer creates almost 350 shm on
>> the
>> > system.
>> >
>> > Is it normal that a single proxy_balancer creates so many shm ?
>>
>> How many VirtualHost(s) do you use in your configuration?
>> Also, how do you declare the balancer(s), in each VirtualHost or in
>> the main section using BalancerInherit on?
>>
>> >
>> > Do i really have to increase the memory segment on my system in huge
>> > proportion to handle all my proxy_balancers ?
>>
>> The number of IPC SysV shared-memory segments is limited to 32768 on
>> linux (system wide), and you are already above with 100 * 350, so you
>> would need to use another SHM mechanism.
>> Unfortunately, there no equivalent to the Mutex directive for shared
>> memories, AFAIK this can't be changed by httpd's configuration.
>> So you would have to recompile the APR library used by your Apache 2.4
>> (you probably did that already since RHEL 6.4 does not seem to package
>> 2.4 by default), and do for example "./configure --enable-posix-shm
>> ..." to use another shared-memory mechanism.
>> The number of segments would then be limited by the usual number of
>> file descriptors per process (ulimit -n).
>>
>> However 350 shm per balancer looks weird to me, your configuration may
>> do something not optimal...
>>
>> Regards,
>> Yann.
>>
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