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From bugzi...@apache.org
Subject [Bug 56977] segfaults when using mod_mem_cache + mod_disk_cache on a reverse proxy with mod_proxy + mod_proxy_http
Date Fri, 12 Sep 2014 18:59:57 GMT
https://issues.apache.org/bugzilla/show_bug.cgi?id=56977

--- Comment #5 from Yann Ylavic <ylavic.dev@gmail.com> ---
(In reply to bpkroth from comment #3)
> (In reply to Ruediger Pluem from comment #2)
> > Honest opinion: Don't use mod_mem_cache. It does not speed up things
> > compared to mod_disk_cache. mod_mem_cache's cache is not shared between
> > different httpd processes. So you waste more memory for getting less
> > performance. Given that you have enough memory in your server mod_disk_cache
> > content is kept in the buffer caches by the OS. If you don't use SSL stuff
> > is send via sendfile which moves stuff from the buffer caches to the socket
> > directly inside the kernel. If you are using SSL stuff will need to be MMAP
> > which is still very fast.
> 
> Yeah, I don't disagree.  Under very high load there is a difference between
> mod_mem_cache and mod_disk_cache in so far as the latter requires some extra
> syscalls to the OS for file permissions and handles and the like, which can
> be particularly expensive in a VM environment, but that is kind of an edge
> case.

A good alternative is also to use mod_disk_cache on a directory which a
(mounted) ramdisk cache.

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