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Re: Why named shared memory zones

September 28, 2009 11:44AM
On Mon, Sep 28, 2009 at 06:25:37PM +0300, Marcus Clyne wrote:

> Hi,
>
> Igor Sysoev wrote:
> > On Mon, Sep 28, 2009 at 03:28:44PM +0300, Marcus Clyne wrote:
> >
> >
> >> Hi,
> >>
> >> What's the purpose/benefit of naming shared memory zones in config files?
> >>
> >
> > Its names are used in other directives. For example, you may have
> > several proxy_cache's.
> >
> >
> I understand their use in other directives, but I was just wondering why
> you actually need them in the directives.
>
> For example, if you define several proxy caches, then each one would
> automatically use a different shared memory section. It seems
> unnecessary to me to use names in the config file, since they'd always
> be different, and from what I gather, if you use the same name (and tag)
> for two shared memory sections, then you'll get a conf error (correct me
> if I'm wrong, though).
>
> I feel that having the config like
>
> proxy_cache_path /data/nginx/cache levels=1:2 10m;
>
> or even
>
> proxy_cache_path /data/nginx/cache 1:2 10m;
>
> would be much neater than
>
> proxy_cache_path /data/nginx/cache levels=1:2 key_zone=one:10m;
>
> And overall wouldn't lose any information that couldn't be generated in
> the background.

No, suppose the following:

proxy_cache_path /data/nginx/cache1 levels=1:2 keys_zone=ONE:10m;
proxy_cache_path /data/nginx/cache2 levels=1:2 keys_zone=TWO:10m;

location / {
proxy_cache ONE;
}

location /one/ {
proxy_cache ONE;
}

location /two/ {
proxy_cache TWO;
}

> > The second reason is Win32 uses named shared memory mapping.
> > However, it's lamost impossible to use shared memory in Win32 due to
> > Vista ASLR.
> >
> If you need to have named sections, it would be easy enough to generate
> them sequentially (e.g. ngx_shms1, ngx_shms2...) whilst reading the
> config file.

The zone name is also logged when zone is out of space.


--
Igor Sysoev
http://sysoev.ru/en/
Subject Author Posted

Why named shared memory zones

Marcus Clyne September 28, 2009 08:32AM

Re: Why named shared memory zones

Igor Sysoev September 28, 2009 08:52AM

Re: Why named shared memory zones

Marcus Clyne September 28, 2009 11:34AM

Re: Why named shared memory zones

Igor Sysoev September 28, 2009 11:44AM

Re: Why named shared memory zones

Marcus Clyne September 28, 2009 12:08PM

Re: Why named shared memory zones

Igor Sysoev September 28, 2009 12:20PM

Re: Why named shared memory zones

Marcus Clyne September 28, 2009 01:00PM

Re: Why named shared memory zones

Igor Sysoev September 28, 2009 03:36PM

Re: Why named shared memory zones

Marcus Clyne September 28, 2009 04:48PM

Re: Why named shared memory zones

Maxim Dounin September 28, 2009 07:32PM

Re: Why named shared memory zones

Marcus Clyne September 28, 2009 08:10PM



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