[mythtv-users] 32 vs. 64 bit, any significant difference?

f-myth-users at media.mit.edu f-myth-users at media.mit.edu
Fri Dec 18 03:39:55 UTC 2009

    > Date: Thu, 17 Dec 2009 15:52:14 -0600
    > From: Johnny Walker <johnnyjboss at gmail.com>

    > > I have an old 0.20 combo BE/FE machine with 2 GB of RAM in it, and I've
    > > never it seen it use more than 1GB. I'm now sorry I put that extra GB into it.
    > >
    > > Unless you are using it for something else in addition to Myth, there's not
    > > much point in even 4GB in a Myth machine.

    > I'm surprised to hear that - MythWeb (Apache) and MySQL use up 1Gb of
    > memory running the canned all movies search for me. Maybe you don't
    > have as many channels as I do.

Indeed.  My backend was thrashing terribly during scheduling with only
1G in it, but it has a large oldrecorded table, many rules, and many
PVR tuners, each with quite a lot of buffers configured---so up to
500meg was encoder buffering alone, squeezing out MySQL and myth.
The problem got slowly worse as both recorded & oldrecorded grew, and I
noticed maybe a year ago when it finally tipped over the threshold and
the machine started paging escessively; it was fine with only 1G when
the machine was young.

So far, with 2GB in it, no problem.  This is all SD on a master
backend with no frontend; that's a different box.  But I've probably
got an unusual configuration.

[By "terribly", I mean 8+ minutes -per scheduler run-.  With more
memory, it now takes about 90 seconds start to finish, including both
the MySQL-heavy phase (~40s) and the mythbackend-heavy phase (~50s),
and more the first time the scheduler has run in a while (because it
can spend up to an additional 30-50s paging in all the MySQL tables
if they've been flushed out to disk in favor of filesystem buffering
for video files.)  But I've got a lot of recording rules and it's an
Athlon 2800+.  Various improvements also went into the scheduler in
later releases, so I expect this to improve when I upgrade.)

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