Messages in this thread | | | Date | Thu, 26 Jul 2007 05:59:53 +0200 | From | Rene Herman <> | Subject | updatedb |
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On 07/25/2007 07:15 PM, Robert Deaton wrote:
> On 7/25/07, Rene Herman <rene.herman@gmail.com> wrote:
>> And there we go again -- off into blabber-land. Why does swap-prefetch >> help updatedb? Or doesn't it? And if it doesn't, why should anyone >> trust anything else someone who said it does says?
> I don't think anyone has ever argued that swap-prefetch directly helps > the performance of updatedb in any way
People have argued (claimed, rather) that swap-prefetch helps their system after updatedb has run -- you are doing so now.
> however, I do recall people mentioning that updatedb, being a ram > intensive task, will often cause things to be swapped out while it runs > on say a nightly cronjob.
Problem spot no. 1.
RAM intensive? If I run updatedb here, it never grows itself beyond 2M. Yes, two. I'm certainly willing to accept that me and my systems are possibly not the reference but assuming I'm _very_ special hasn't done much for me either in the past.
The thing updatedb does do, or at least has the potential to do, is fill memory with cached inodes/dentries but Linux does not swap to make room for caches. So why will updatedb "often cause things to be swapped out"?
[ snip ]
> Swap prefetch, on the other hand, would have kicked in shortly after > updatedb finished, leaving the applications in swap for a speedy > recovery when the person comes back to their computer.
Problem spot no. 2.
If updatedb filled all of RAM with inodes/dentries, that RAM is now used (ie, not free) and swap-prefetch wouldn't have anywhere to prefetch into so would _not_ have kicked in.
So what's happening? If you sit down with a copy op "top" in one terminal and updatedb in another, what does it show?
Rene.
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