Re: Getting FS access events

Richard Gooch
2001-05-14T04:27:47Z

Rik van Riel writes:
> On Sun, 13 May 2001, Richard Gooch wrote:
> > Larry McVoy writes:
>
> > > Ha. For once you're both wrong but not where you are thinking. One
> > > of the few places that I actually hacked Linux was for exactly this
> > > - it was in the 0.99 days I think. I saved the list of I/O's in a
> > > file and filled the buffer cache with them at next boot. It
> > > actually didn't help at all.
> >
> > Maybe you did something wrong :-)
>
> How about "the data loads got instrumented, but the metadata
> loads which caused over half of the disk seeks didn't" ?
>
> (just a wild guess ... if it turns out to be true we may want
> to look into doing agressive readahead on inode blocks ;))

Caching metadata is definately part of my cunning plan. I'd like to
think that once Al's metadata-in-page-cache patches go in, we'll get
that for free.

However, that will still leave indirect blocks unordered. I don't see
a clean way of fixing that. Which is why doing things at the block
device layer has it's attractions (except it doesn't work).

Hm. Is there a reason why the page cache can't see if a a block is in
the block cache, and read it from there first?

Regards,

Richard....
Permanent: rgooch@atnf.csiro.au
Current: rgooch@ras.ucalgary.ca