Re: [patch] `cp /dev/zero /tmp' (patch against 2.2.9)

Linus Torvalds (torvalds@transmeta.com)
Fri, 18 Jun 1999 16:59:30 -0700 (PDT)


On Sat, 19 Jun 1999, Stephen C. Tweedie wrote:
>
> Yes, we do. The penalty of having to walk the entire inode indirection
> tree to find dirty indirection buffers is still there otherwise, and
> that is really expensive for large files (although not so expensive as
> it used to be when we needed to do a buffer lookup for each entry).

It's cut down by a factor of thousand on a 4k filesystem.

AND on top of that the lookup is faster anyway, because there are much
fewer buffers on the hashes.

> The
> per-inode dirty buffer list eliminates that scan entirely, and allows us
> to unify the O_SYNC and fdatasync code.

Why do you want that unified? Have you looked at my stuff - it does
fdatasync() very cleanly.

> The other thing I'll fix is the wait-on-page ordering: we want to wait
> in the reverse order that we submit the IOs in, to try to minimise the
> number of unnecessary wakeups we encounter.

I doubt that really matters, but that can be timed.

Linus

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