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From Jim Jagielski <...@jaguNET.com>
Subject Re: [users@httpd] Apache 2.4 create a huge amount of shared memory segments
Date Tue, 23 Dec 2014 13:49:54 GMT
So is the main issue the amount of shm used, right?

> On Dec 19, 2014, at 5:04 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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