On Thu, Sep 06, 2012 at 07:34:18PM -0600, Jens Axboe wrote: > On 2012-09-06 16:34, Kent Overstreet wrote: > > Reusing bios is something that's been highly frowned upon in the past, > > but driver code keeps doing it anyways. If it's going to happen anyways, > > we should provide a generic method. > > > > This'll help with getting rid of bi_destructor - drivers/block/pktcdvd.c > > was open coding it, by doing a bio_init() and resetting bi_destructor. > > > > This required reordering struct bio, but the block layer is not yet > > nearly fast enough for any cacheline effects to matter here. > > That's an odd and misplaced comment. Was just doing testing today at 5M > IOPS, and even years back we've had cache effects for O_DIRECT in higher > speed setups. Ah, I wasn't aware that you were pushing that many iops through the block layer - most I've tested myself was around 1M. It wouldn't surprise me if cache effects in struct bio mattered around 5M... > That said, we haven't done cache analysis in a long time. So moving > members around isn't necessarily a huge deal. Ok, good to know. I've got another patch coming later that reorders struct bio a bit more, for immutable bvecs (bi_sector, bi_size, bi_idx go into a struct bvec_iter together). > Lastly, this isn't a great commit message for other reasons. Anyone can > see that it moves members around. It'd be a lot better to explain _why_ > it is reordering the struct. Yeah, I suppose so. Will keep that in mind for the next patch. > > BTW, I looked over the rest of the patches, and it looks OK to me. Resent them. Thanks! -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
