Re: review: increase bulkstat readahead window

[Christoph Hellwig <hch@infradead.org>]

On Tue, Jul 25, 2006 at 01:50:04PM +1000, Nathan Scott wrote:
> Hi all,
>     
> We limit the amount of bulkstat readahead we can issue based on 
> the size of the array of inode cluster records (irbuf), which we
> allocate on each bulkstat call.  Increasing the size of this array
> has shown noticable performance improvements, and given bulkstat
> is always called to scan the filesystem from one end to the other,
> we're going to have to issue that IO at some point, may as well do
> it up front.  We don't want to get silly in sizing this buffer, 
> though, as it needs to be a contiguous chunk of memory.  Here I've
> increased it from 1 page to 4 pages, with some logic to halve the
> size incrementally if we cant allocate that successfully (as we do
> in one or two other places in XFS, for other things).

ok.  I wonder whether we should add a generic kmalloc_leastmost routine
(with a name better than that of course..)