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). -- Milosz Tanski CTO 16 East 34th Street, 15th floor New York, NY 10016 p: 646-253-9055 e: milosz@xxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
