On Fri, Jan 16, 2015 at 11:55 AM, Jeremy Allison <jra@xxxxxxxxx> wrote: > 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 ! I have the first version of the FIO cifs support via samba in my fork of FIO here: https://github.com/mtanski/fio/tree/samba Right now it only supports sync mode of FIO (eg. can't submit multiple outstanding requests) but I'm looking into how to make it work with smb2 read/write calls with the async flag. Additionally, I'm sure I'm doing some things not quite right in terms of smbcli usage as it was a decent amount of trial and error to get it to connect (esp. the setup before smbcli_full_connection). Finally, it looks like the more complex api I'm using (as opposed to smbclient, because I want the async calls) doesn't quite fully export all calls I need via headers / public dyn libs so it's a bit of a hack to get it to build: https://github.com/mtanski/fio/commit/7fd35359259b409ed023b924cb2758e9efb9950c#diff-1 But it works for my randread tests with zipf and the great part is that it should provide a flexible way to test samba with many fake clients and access patterns. So... progress. -- Milosz Tanski CTO 16 East 34th Street, 15th floor New York, NY 10016 p: 646-253-9055 e: milosz@xxxxxxxxx -- 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>