On Tue, May 14, 2019 at 03:51:42PM +0200, Christoph Hellwig wrote: > On Tue, May 14, 2019 at 05:05:45PM +0800, Ming Lei wrote: > > However we still may make it better, for example, the attached patch can > > save 10~20% time when running 'mkfs.ntfs -s 512 /dev/vda', lots of small > > request(63KB) can be merged to big IO(1MB). > > And we could save even more time by making the block dev buffered I/O > path not do stupid things to start with. I am wondering if it can be done easily, given mkfs is userspace which only calls write syscall on block device. Or could you share something about how to fix the stupid things? > > > > With the gap devices we have unlimited segment size, see my next patch > > > to actually enforce that. Which is much more efficient than using > > > > But this patch does effect on non-gap device, and actually most of > > device are non-gap type. > > Yes, but only for request merges, and only if merging the requests > goes over max_requests. The upside is that we actually get a > nr_phys_segments that mirrors what is in the request, fixing bugs > in a few drivers, and allowing for follow on patches that significantly > simplify our I/O path. non-gap device still has max segment size limit, and I guess it still needs to be respected. Thanks, Ming
