Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

[Rene Herman <rene.herman@gmail.com>]

On 07/27/2007 07:45 PM, Daniel Hazelton wrote:

> Updatedb or another process that uses the FS heavily runs on a users
> 256MB P3-800 (when it is idle) and the VFS caches grow, causing memory
> pressure that causes other applications to be swapped to disk. In the
> morning the user has to wait for the system to swap those applications
> back in.
>
> Questions about it:
> Q) Does swap-prefetch help with this? 
> A) [From all reports I've seen (*)] Yes, it does. 

No it does not. If updatedb filled memory to the point of causing swapping 
(which noone is reproducing anyway) it HAS FILLED MEMORY and swap-prefetch 
hasn't any memory to prefetch into -- updatedb itself doesn't use any 
significant memory.

Here's swap-prefetch's author saying the same:

http://lkml.org/lkml/2007/2/9/112

| It can't help the updatedb scenario. Updatedb leaves the ram full and
| swap prefetch wants to cost as little as possible so it will never
| move anything out of ram in preference for the pages it wants to swap
| back in.

Now please finally either understand this, or tell us how we're wrong.

Rene.

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