Fwd: [PATCH] Add load average support to makehistory

Russ Allbery rra at stanford.edu
Mon Jun 22 16:41:05 UTC 2009

"Jonathan Kamens" <jik at kamens.brookline.ma.us> writes:

> Russ Allbery wrote, "This seems like sort of a hacky way to
> approximate the same thing that nice would do in a much better and
> finer-grained way.  But maybe I'm missing something?"
> The problem is that nice will not handle the problem the patch is
> trying to solve in a better and finer-grained way.  In fact, nice
> won't help with the problem at all.
> Nice changes the scheduling priority of a process, i.e., what
> proportion of available CPU cycles it is allocated.  However, the
> resource that gets overwhelmed when makehistory is running is not CPU,
> but rather disk I/O.  When makehistory hoses the disk, a bunch of
> processes will get stuck in disk wait, which means that there will be
> plenty of CPU available for the processes that aren't, which means
> that even if you nice makehistory all the way up to 20, it'll still
> get plenty of CPU to continue hosing the disk.

Oh, huh.  Wow, that feels like a bug in the way that prioritization is
handled to me, but I can see how it would fall out that way.  In that
case, I have no objections to apply this patch.

Do you think this method is needed for anything other than makehistory?
Do you have trouble with expireover, for instance?

Russ Allbery (rra at stanford.edu)             <http://www.eyrie.org/~eagle/>

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