On Fri, Feb 28, 2014 at 07:01:50AM +1100, Dave Chinner wrote: > On Thu, Feb 27, 2014 at 09:08:46AM -0500, Brian Foster wrote: > > On Thu, Feb 27, 2014 at 08:51:14PM +1100, Dave Chinner wrote: > > > From: Dave Chinner <dchinner@xxxxxxxxxx> > > > > > > > Hmm, I replied to this one in the previous thread, but now I notice that > > it apparently never made it to the list. Dave, did you happen to see > > that in your inbox? Anyways, I had a couple minor comments/questions > > that I'll duplicate here (which probably don't require another > > repost)... > > No, I didn't. > > [snip typos that need fixing] > > > > diff --git a/repair/prefetch.c b/repair/prefetch.c > > > index aee6342..7d3efde 100644 > > > --- a/repair/prefetch.c > > > +++ b/repair/prefetch.c > > > @@ -866,6 +866,48 @@ start_inode_prefetch( > > > return args; > > > } > > > > > > > A brief comment before the prefetch_ag_range bits that explain the > > implicit design constraints (e.g., throttle prefetch based on > > processing) would be nice. :) > > Can do. Added this: /* * prefetch_ag_range runs a prefetch-and-process loop across a range of AGs. It * begins with @start+ag, and finishes with @end_ag - 1 (i.e. does not prefetch * or process @end_ag). The function starts prefetch on the first AG, then loops * starting prefetch on the next AG and then blocks processing the current AG as * the prefetch queue brings inodes into the processing queue. * * There is only one prefetch taking place at a time, so the prefetch on the * next AG only starts once the current AG has been completely prefetched. Hence * the prefetch of the next AG will start some time before the processing of the * current AG finishes, ensuring that when we iterate an start processing the * next AG there is already a significant queue of inodes to process. * * Prefetch is done this way to prevent it from running too far ahead of the * processing. Allowing it to do so can cause cache thrashing, where new * prefetch causes previously prefetched buffers to be reclaimed before the * processing thread uses them. This results in reading all the inodes and * metadata twice per phase and it greatly slows down the processing. Hence we * have to carefully control how far ahead we prefetch... */ Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
