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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. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||
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