On Thu, Jul 24, 2014 at 7:16 AM, Zach Brown <zab@xxxxxxxxx> wrote: > On Thu, Jul 24, 2014 at 06:55:28AM +0800, Ming Lei wrote: >> From: Dave Kleikamp <dave.kleikamp@xxxxxxxxxx> >> >> This adds an interface that lets kernel callers submit aio iocbs without >> going through the user space syscalls. This lets kernel callers avoid >> the management limits and overhead of the context. It will also let us >> integrate aio operations with other kernel apis that the user space >> interface doesn't have access to. >> >> This patch is based on Dave's posts in below links: >> >> https://lkml.org/lkml/2013/10/16/365 >> https://groups.google.com/forum/#!topic/linux.kernel/l7mogGJZoKQ > > This was originally written a billion years ago when dinosaurs roamed > the earth. Also, notably, before Kent and Ben reworked a bunch of the Not so far away, this patch is based on Dave's last version of V9, which was posted in Oct, 2013, :-) > aio core. I'd want them to take a look at this patch to make sure that > it doesn't rely on any assumptions that have changed. Looks I missed to Cc Ken, :-( > >> +/* opcode values not exposed to user space */ >> +enum { >> + IOCB_CMD_READ_ITER = 0x10000, >> + IOCB_CMD_WRITE_ITER = 0x10001, >> +}; > > And I think the consensus was that this isn't good enough. Find a way > to encode the kernel caller ops without polluting the uiocb cmd name > space. That is easy, since the two cmd names are only for kernel AIO, whatever should be OK, but looks I didn't see such comment. > > (I've now come to think that this entire approach of having loop use aio > is misguided and that the way forward is to have dio consume what loop > naturally produces -- bios, blk-mq rqs, whatever -- but I'm on to other Yes, that is what these patches are doing, and actually AIO's model is a good match to driver's interface. Lots of drivers use the asynchronous model(submit, complete, ...). > things these days.) At least, loop can improve its throughput much by kernel AIO without big changes to fs/direct-io(attribute much to ITER_BVEC), and vhost-scsi should benefit from it too. Thanks, -- 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
