Re: VFS scalability (was: [rfc] lockless pagecache)

Andi Kleen
2005-06-27T07:16:26Z

Nick Piggin <nickpiggin@yahoo.com.au> writes:

> This is with the filesystem mounted as noatime, so I can't work
> out why update_atime is so high on the list. I suspect maybe a
> false sharing issue with some other fields.

Did all the 64CPUs write to the same file?

Then update_atime was just the messenger - it is the first function
to read the inode so it eats the cache miss overhead.

Maybe adding a prefetch for it at the beginning of sys_read()
might help, but then with 64CPUs writing to parts of the inode
it will always thrash no matter how many prefetches.

-Andi