On 2011年11月01日 17:00, Zhu Yanhai Wrote: > The current libaio/aio has to be Direct-IO, otherwise it falls back into sync IO. > However, the aio core has already been asychronous naturally. This patch adds a complete > notify mechanism to implement buffer aio, the main idea is to readahead()-like in > io_submit(), counts the non-uptodated pages assocaiated with each iocb, then put each ref > in the bio complete path just before unlock_page(), and hook them on to the aio ring buffer > finally when the ref drops to zero. In io_getevents(), we call vfs_read() as a safe net > since there is still little possibility that the pages had brought in were reclaimed > between io_submit() and io_getevents(). > > I have tested this patch for a while, for the small size random io request, its > performance is more or less the same with the traditional aio, for the big io request, > the overhead of one extra memory copy arises. > > I think so far it has at least below obvious drawbacks, > > * mpage_readpage() is a really narrow interface, I have no way to pass down > the new control struct baiocb, so I just put it into struct task_struct and > refer it by current() as a workaround. > > * the do_baio_read() routine is heavily similar with do_generic_file_read(), but > the latter is really hard to modify. I think we may stuff these code down into the > readahead path to reduce code reduplication. > > Hopefully the explanations are clear enough and don't muddy the water any worse. > I figure the code does need some better comments, and any suggestion are welcome. > > Signed-off-by: Zhu Yanhai <gaoyang.zyh@xxxxxxxxxx> > > --- > fs/aio.c | 319 ++++++++++++++++++++++++++++++++++++++++++- > fs/buffer.c | 26 ++++- > fs/mpage.c | 28 ++++- > include/linux/aio.h | 9 ++ > include/linux/aio_abi.h | 1 + > include/linux/blk_types.h | 2 + > include/linux/buffer_head.h | 3 + > include/linux/page-flags.h | 2 + > include/linux/sched.h | 1 + > 9 files changed, 386 insertions(+), 5 deletions(-) > Hmm, I don't see the usage from user space. Is it possible to post a demo code in user space, so people are able to understand how to use/test your patch. BTW, if there is any performance number, it should be interesting, too. Thanks. -- Coly Li -- 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
