Re: updatedb

Mike Galbraith
2007-07-27T11:48:00Z

On Fri, 2007-07-27 at 13:09 +0200, Rene Herman wrote:
> On 07/27/2007 11:26 AM, Mike Galbraith wrote:
>

> > Updatedb finishes, freeing some ram (doesn't matter how much)
>
> Will be very little and swap-prefetch at least in its current form needs
> more than very little to start doing anything:
>
> http://ck.kolivas.org/patches/swap-prefetch/2.6.21-swap_prefetch-38.patch
>
> | /*
> | * Set max number of entries to 2/3 the size of physical ram as we
> | * only ever prefetch to consume 2/3 of the ram.
> | */
>
> However, okay, let's just ignore that and pretend it kicks in even with the
> little free memory updatedb itself left behind when it finished:

Hm. I didn't read the patch, so I'm only going on what you quoted.
>From that, all I see is a limit on how much will be used total, and 2/3
of physical ram is a bunch. This quote doesn't say free ram, it says
physical ram. If it really does use only free ram, that indeed sounds
pretty pointless. I believe the users who say their apps really do get
paged back in though, so suspect that's not the case.

Anyway, I only offered a simple explanation of how swap-prefetching can
indeed help (and possibly hurt) with something like updatedb, not an
analysis of it's current implementation ;-) I'd have to read it, and
test it myself to do that, but my world doesn't have a need for it,
so...

-Mike