Messages in this thread | | | From | Eric Dumazet <> | Subject | Re: [PATCH 2.6.19-rc3] VFS: per-sb dentry lru list | Date | Mon, 30 Oct 2006 17:09:31 +0100 |
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On Monday 30 October 2006 16:34, Kirill Korotaev wrote: > > Quick search maybe, but your patch adds 2 pointers to each dentry in the > > system... That's pretty expensive, as dentries are already using a *lot* > > of ram. > > I don't see much problems with it... it is cache and it can be pruned if > needed. Some time ago, for example, my patch introducing the same list for > inodes was commited.
The ratio of dentries/PAGE is higher than ration of inodes/PAGE. (On a x86_64 machine, 19 dentries per PAGE, 5 ext3 inodes per PAGE=
Therefore I suspect that the number of pages locked in dentry_cache because of one inuse dentry is higher.
> > > Maybe an alternative would be to not have anymore a global dentry_unused, > > but only per-sb unused dentries lists ? > > I don't know global LRU implementation based on per-sb lists, do you? > If someone suggest the algorithm for more or less fair global LRU > based on non-global list we will implement it. However, so far, > AFAICS there were problems with it.
Using 32 bytes per dentry for unused LRUs sounds too much, maybe we should revert LRUS handling to timestamps or things like that.
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