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From Josh Beck <j...@zcompany.com>
Subject Re: general/2669: Files being served are loaded into memory then served
Date Thu, 23 Jul 1998 02:10:01 GMT
The following reply was made to PR general/2669; it has been noted by GNATS.

From: Josh Beck <josh@zcompany.com>
To: Marc Slemko <marcs@znep.com>
Cc: apbugs@apache.org
Subject: Re: general/2669: Files being served are loaded into memory then served
Date: Wed, 22 Jul 1998 17:54:34 -0700 (PDT)

 > Yes, Apache uses mmap().  If you want to disable it, remove the
 > USE_MMAP_FILES define from the appropriate section of the include/conf.h
 > file.
 > 
 > However, if you think you want to stop it from using mmap() then you are
 > probably wrong, especially on FreeBSD.  You will not magically gain the
 > amount of memory listed by ps or top by stopping using mmap().
 
 No, I don't plan on gaining that much back, and buying more memory isn't a
 problem. What I'd like to do is avoid the problem we may encounter when
 there are downloads of 200 simultaneous (different) songs going on, say,
 where we would need 1GB of ram to mmap all the files so they can be served
 simultaneously. Yes, we can buy 1 GB or ram, but that stops becoming a
 valid solution really quickly, as the price of machine and the ram for a
 machine that can handle that much memory are very high. 
 
 Something else I just thought of is that the problem isn't helped by
 splitting downloads across multiple machines, as each machine would need
 an equal amount of ram. :( I mean, we can buy 512 M or 1 G of ram for one
 PC, or for several, but we can't just go out and buy a Sparc or something
 with 10 G of ram simply to fit all files currently being downloaded into
 memory. 
 
 If I stop using mmap, I imagine that there would be performance issues
 introduced in that more disk accesses would be required to keep the buffer
 cache up to date (particularly with different instances of apache serving
 different portions of any specific file), but if this is a lesser problem
 than the issues caused by mmap(), are there any reasons not to do this? 
 
 Josh Beck                                                 josh@zcompany.com
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