On Thu, Dec 13 2007, Mark Lord wrote: > Matthew Wilcox wrote: > >On Thu, Dec 13, 2007 at 01:48:18PM -0500, Mark Lord wrote: > >>Problem confirmed. 2.6.23.8 regularly generates segments up to 64KB for > >>libata, > >>but 2.6.24 uses only 4KB segments and a *few* 8KB segments. > > > >Just a suspicion ... could this be slab vs slub? ie check your configs > >are the same / similar between the two kernels. > .. > > Mmmm.. a good thought, that one. > But I just rechecked, and both have CONFIG_SLAB=y > > My guess is that something got changed around when Jens > reworked the block layer for 2.6.24. > I'm going to dig around in there now. I didn't rework the block layer for 2.6.24 :-). The core block layer changes since 2.6.23 are: - Support for empty barriers. Not a likely candidate. - Shared tag queue fixes. Totally unlikely. - sg chaining support. Not likely. - The bio changes from Neil. Of the bunch, the most likely suspects in this area, since it changes some of the code involved with merges and blk_rq_map_sg(). - Lots of simple stuff, again very unlikely. Anyway, it sounds odd for this to be a block layer problem if you do see occasional segments being merged. So it sounds more like the input data having changed. Why not just bisect it? -- Jens Axboe - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
