Re: Asynch I/O gets easily overloaded on 2.2.15 and 2.3.99

From: Andi Kleen (ak@suse.de)
Date: Tue Apr 11 2000 - 11:02:20 EST


On Tue, Apr 11, 2000 at 05:05:39PM +0200, Andrea Arcangeli wrote:
> >The main problem with the dentry and inode hashes is that they waste twice
> >the memory they should (anchored list heads are *very* wasteful for hash
> >tables). It is rather unlikely that the cost of the few saved if()s in the
> >list macros weight up for the additional cache misses [patch will come
> >as soon as I have tested it a bit more]
>
> You are perfectly right, but I really don't think it's for the speed but
> for being allowed to use the list.h interface (at least that's why I used
> the anchored list head in the write-COW fast path lookup of the
> lvm-snapshot code even if I known I wasn't optimizing memory usage ;). I
> strongly disagree in adding further by hand stuff like what we have just
> for the buffer and page cache hashtables. We do need the same interface of
> list.h _but_ that uses a single word sized head.

Yes, I did a hlist[1] for this purpose. It does not have the 100% same interface
because the semantics are a bit different.

-Andi

[1] suggestions for better names are welcome

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