Speeding up VFS using HW assist

Speeding up VFS using HW assist

[Bharath Madhavan]

Hello All,
	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.

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?)

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)

Would tweaking the buffer cache and page cache sizes make a considerable 
effect on efficiency?

Any other suggestions?

Thanks a lot,

Bharath

Re: Speeding up VFS using HW assist

[Pavel Machek]

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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