Re: [PATCH] Re: memory usage - dentry_cacheg

Alexander Viro
2001-04-13T02:04:17Z

On Thu, 12 Apr 2001, Ed Tomlinson wrote:

> On Thursday 12 April 2001 11:12, Alexander Viro wrote:
> What prompted my patch was observing situations where the icache (and dcache
> too) got so big that they were applying artifical pressure to the page and
> buffer caches. I say artifical since checking the stats these caches showed
> over 95% of the entries unused. At this point there is usually another 10%
> or so of objects allocated by the slab caches but not accounted for in the
> stats (not a problem they are accounted if the cache starts using them).

"Unused" as in "->d_count==0"? That _is_ OK. Basically, you will have
positive ->d_count only on directories and currently opened files.
E.g. during compile in /usr/include/* you will have 3-5 file dentries
with ->d_count > 0 - ones that are opened _now_. It doesn't mean that
everything else rest is unused in any meaningful sense. Can be freed - yes,
but that's a different story.

If you are talking about "unused" from the slab POV - _ouch_. Looks like
extremely bad fragmentation ;-/ It's surprising, and if that's thte case
I'd like to see more details.
Al