Messages in this thread | | | Date | Thu, 28 Jul 2011 15:09:48 -0700 | Subject | Re: [PATCH] dio: Fast-path for page-aligned IOs | From | Daniel Ehrenberg <> |
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On Wed, Jul 27, 2011 at 2:08 PM, Christoph Hellwig <hch@infradead.org> 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?
I'm having a little trouble getting his patch working. I hope to have this data soon, but I've been distracted by some other things. > > 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.
Are you talking about special-casing a raw block device? I'd like the optimization to also work with a file system to support a particular workload I've been looking at.
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