Coly Li <i@xxxxxxx> writes: > 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. He added a new IOCB_CMD_blah for buffered aio reads. That is, unfortunately, a really poor way to go about doing things. Please take a look at the work Jens did on implementing buffered aio. It can be found in his linux-block git tree. Cheers, Jeff -- 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
