Mailinglist Archive: opensuse-wiki (177 mails)

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Re: [opensuse-wiki] Performance Options
  • From: Marcus Rueckert <darix@xxxxxxxxx>
  • Date: Tue, 17 Aug 2010 20:44:21 +0200
  • Message-id: <20100817184421.GL8921@xxxxxxxxxxxx>
On 2010-08-17 12:37:01 -0600, Matthew Ehle wrote:
I highly doubt that apc cache is much faster than memcached.

It mostly depends on how the wiki is used (amount of read vs. write),
but the general consensus is that APC is slightly faster for most
situations.

As the former co maintainer of the wiki I know very well that the cache
access was the fastest part of it. :)

In a proper config you got one memcached per webserver, and configure
all memcacheds in the wiki.

Each web server has its own memcached daemon, which is used by only
that web server. We can always pool them, but it would make very
little difference for our setup.

well, except that you cache things multiple times and might hit stale
caches that way. I would recommend to configure it to use all running
mecacheds

a) you got shared storage, no matter on which webserver you get the
request. I would assume that the APC is local to the machine.
Yes, and that is why it is slightly faster. APC is accessed locally,
while memcached is accessed through a network socket, even on
localhost.

1. access via localhost is shortcutted in the kernel for tcp. so if you
only use it via localhost the overhead is pretty low.

b) you can scale to much more cache with memcached than with APC.
Yes, but we don't have enough data for that to be relevant quite yet.
I run memcached to store up to 1GB of data, but I don't think we even
come close to hitting that.

c) memcached is fast enough for wikipedia and even facebook (although
they use it with udp in the mean time)

Agreed. I think that it is a perfectly acceptable solution. I just
wanted to bring up the APC alternative as a possibility. I might have
to look into running memcached with UDP, as that might cut some of the
network overhead.

if you want to keep the localhost only solution, the recent memcached
versions support listening on a unix domain socket (see -s param).

anyway ... I think we are far away from the workload that warrants the
switch to udp.

darix

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