Re: Speeding up VFS using HW assist

[Pavel Machek <pavel@suse.cz>]

Hi!

> 	I will be using Linux as the OS for an embedded system.
> I was looking into 2.4.4 kernel code and saw the dcache implementation
> in VFS which is pretty neat and fast by itself.
> 
> My question is, will I gain any considerable efficiency in file system
> access
> if I can move this "pathname -> inode" lookup into some proprietery 
> HW assist mechanism and take out the dcache hashing and "cached_lookup"
> function.

I doubt it will do much difference. How much time is spent in kernel
in your workload? What kind of embedded system is that?

> How good(bad) was it before the dcache implementation and in which release
> was dcache feature added (was it only after 2.2.x release). 
> Did we get 2-3 times better performance with dcache? (if not, how much?)

I'd be surprised if dcache made more than 20% speedup.

> Can anyone suggest any other place in the file system (VFS and EXT2) where
> we
> can use any HW assist (let us say FPGA implementing search, lookup, etc.)
> to speed up file-system access (both for opening and read/write)

Dumping ext2 for reiserfs? ;-)


-- 
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details at http://atrey.karlin.mff.cuni.cz/~pavel/velo/index.html.