Re: [Kiobuf-io-devel] RFC: Kernel mechanism: Compound event wait

[James Sutherland]

On Thu, 8 Feb 2001, Rik van Riel wrote:

> On Thu, 8 Feb 2001, Mikulas Patocka wrote:
> 
> > > > You need aio_open.
> > > Could you explain this? 
> > 
> > If the server is sending many small files, disk spends huge
> > amount time walking directory tree and seeking to inodes. Maybe
> > opening the file is even slower than reading it
> 
> Not if you have a big enough inode_cache and dentry_cache.

Eh? However big the caches are, you can still get misses which will
require multiple (blocking) disk accesses to handle...

> OTOH ... if you have enough memory the whole async IO argument
> is moot anyway because all your files will be in memory too.

Only for cache hits. If you're doing a Mindcraft benchmark or something
with everything in RAM, you're fine - for real world servers, that's not
really an option ;-)

Really, you want/need cache MISSES to be handled without blocking. However
big the caches, short of running EVERYTHING from a ramdisk, these will
still happen!


James.

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