Re: negative dentries wasting ram

Alexander Viro
2002-05-24T18:00:41Z

On Fri, 24 May 2002, Andrea Arcangeli wrote:

> so why don't you also left a negative directory floating around, so you
> know if you creat a file with such name you don't need to ->loopup the
> lowlevel fs but you only need to destroy the negative directory and all
> its leafs in-core-dcache? If you did the negative effect would become
> more obvious, the d_unhash hides it except for the spooling workloads.

-ENOPARSE

> of kmem_cache_reap, so we are as efficient as possible, but we don't
> risk throwing away very useful cache, for more dubious caching effects
> after an unlink/create-failure that currently have the side effect of
> throwing away tons of worthwhile positive pagecache (and even triggering
> swap false positives) in some workloads.

I might buy that argument if we didn't also leave around _unreferenced_
inodes for minutes in the icache. And _that_ is much stronger source of
memory pressure, so if you want to balance the thing you need to start
there.