On Fri, Jan 16, 2015 at 10:44:12AM -0500, Milosz Tanski wrote: > On Thu, Jan 15, 2015 at 5:31 PM, Jan Kara <jack@xxxxxxx> wrote: > > On Thu 15-01-15 12:43:23, Milosz Tanski wrote: > >> I would like to talk about enhancing the user interfaces for doing > >> async buffered disk IO for userspace applications. There's a whole > >> class of distributed web applications (most new applications today) > >> that would benefit from such an API. Most of them today rely on > >> cobbling one together in user space using a threadpool. > >> > >> The current in kernel AIO interfaces that only support DIRECTIO, they > >> were generally designed by and for big database vendors. The consensus > >> is that the current AIO interfaces usually lead to decreased > >> performance for those app. > >> > >> I've been developing a new read syscall that allows non-blocking > >> diskio read (provided that data is in the page cache). It's analogous > >> to what exists today in the network world with recvmsg with MSG_NOWAIT > >> flag. The work has been previously described by LWN here: > >> https://lwn.net/Articles/612483/ > >> > >> Previous attempts (over the last 12+ years) at non-blocking buffered > >> diskio has stalled due to their complexity. I would like to talk about > >> the problem, my solution, and get feedback on the course of action. > >> > >> Over the years I've been building the low level guys of various "web > >> applications". That usually involves async network based applications > >> (epoll based servers) and the biggest pain point for the last 8+ years > >> has been async disk IO. > > Maybe this topic will be sorted out before LSF/MM. I know Andrew had some > > objections about doc and was suggesting a solution using fincore() (which > > Christoph refuted as being racy). Also there was a pending question > > regarding whether the async read in this form will be used by applications. > > But if it doesn't get sorted out a short session on the pending issues > > would be probably useful. > > > > Honza > > -- > > Jan Kara <jack@xxxxxxx> > > SUSE Labs, CR > > I've spent the better part of yesterday wrapping up the first cut of > samba support to FIO so we can test a modified samba file server with > these changes in a few scenarios. Right now it's only sync but I hope > to have async in the future. I hope that by the time the summit rolls > around I'll have data to share from samba and maybe some other common > apps (node.js / twisted). Don't forget to share the code changes :-). We @ Samba would love to see them to keep track ! -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>