On Wed, 27 Jul 2011 17:08:28 -0400 Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote: > On Mon, Jun 20, 2011 at 04:17:35PM -0700, Dan Ehrenberg wrote: > > The fast path does not apply for operations of the wrong size > > or alignmnent, or for operations on raw drives with 512-byte sectors. > > It might be possible to make this special case a little more general > > while maintaining its performance benefits, but I do not believe that > > the full performance benefits can be achieved without resorting to > > special handling of simple cases, as is done in this patch. > > Did you check how this compares to Andis small optimizations? > > Also operations on raw disks are something people with fast devices > care about a lot. We often hear about benchmark regressions due to > stupid little things in the direct I/O code. > > If we want to special case something that would be a very easy target, > with a 1:1 mapping of logical to physical blocks and thus no need > to call the allocator first, and no need for any kind of locking > or alignment handling. Ken did this back in 2006 (http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=e61c90188b9956edae1105eef361d8981a352fcd) but we reverted that shortly afterwards for some reason. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
