Messages in this thread | | | Date | Thu, 12 Apr 2001 11:42:25 -0400 (EDT) | From | Alexander Viro <> | Subject | Re: [PATCH] Re: Fwd: Re: memory usage - dentry_cacheg |
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On Thu, 12 Apr 2001, Alexander Viro wrote:
> Bad idea. If you do loops over directory contents you will almost > permanently have almost all dentries freeable. Doesn't make freeing > them a good thing - think of the effects it would have. > > Simple question: how many of dentries in /usr/src/linux/include/linux > are busy at any given moment during the compile? At most 10, I suspect. > I.e. ~4%. > > I would rather go for active keeping the amount of dirty inodes low, > so that freeing would be cheap. Doing massive write_inode when we > get low on memory is, indeed, a bad thing, but you don't have to > tie that to freeing stuff. Heck, IIRC you are using quite a similar > logics for pagecache...
PS: with your approach negative entries are dead meat - they won't be caught used unless you look at them exactly at the moment of d_lookup().
Welcome to massive lookups in /bin due to /usr/bin stuff (and no, shell own cache doesn't help - it's not shared; think of scripts).
IOW. keeping dcache/icache size low is not a good thing, unless you have a memory pressure that requires it. More agressive kupdate _is_ a good thing, though - possibly kupdate sans flushing buffers, so that it would just keep the icache clean and let bdflush do the actual IO.
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