On Tue, Nov 20, 2018 at 09:35:07PM -0800, Sagi Grimberg wrote: > > > > Wait, I see that the bvec is still a single array per bio. When you said > > > a table I thought you meant a 2-dimentional array... > > > > I mean a new 1-d table A has to be created for multiple bios in one rq, > > and build it in the following way > > > > rq_for_each_bvec(tmp, rq, rq_iter) > > *A = tmp; > > > > Then you can pass A to iov_iter_bvec() & send(). > > > > Given it is over TCP, I guess it should be doable for you to preallocate one > > 256-bvec table in one page for each request, then sets the max segment size as > > (unsigned int)-1, and max segment number as 256, the preallocated table > > should work anytime. > > 256 bvec table is really a lot to preallocate, especially when its not > needed, I can easily initialize the bvec_iter on the bio bvec. If this > involves preallocation of the worst-case than I don't consider this to > be an improvement. If you don't provide one single bvec table, I understand you may not send this req via one send(). The bvec_iter initialization is easy to do: bvec_iter = bio->bi_iter when you move to a new a bio, please refer to __bio_for_each_bvec() or __bio_for_each_segment(). Thanks, Ming
