[lkml]   [2012]   [Apr]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [RFC PATCH v2 15/21] loop: use aio to perform io on the underlying file
    On 04/20/2012 11:20 AM, Jeff Moyer wrote:
    > Dave Kleikamp<> writes:
    >> On 04/20/2012 09:48 AM, Maxim V. Patlasov wrote:
    >>> On 03/30/2012 07:43 PM, Dave Kleikamp wrote:
    >>>> From: Zach Brown<>
    >>>> This uses the new kernel aio interface to process loopback IO by
    >>>> submitting concurrent direct aio. Previously loop's IO was serialized
    >>>> by synchronous processing in a thread.
    >>> The patch ignores REQ_FLUSH bit of bi_rw. Is it simply overlook?
    >> Good question. Since the loop device is sending only direct IO requests,
    >> it shouldn't be necessary to explicitly flush page cache, but REQ_FLUSH
    > REQ_FLUSH isn't about the page cache, it's about flushing the volatile
    > disk write cache. You need to handle that.

    I guess O_DIRECT doesn't routinely issue flushes simply because it's too
    expensive? Apps that care about consistent IO and O_DIRECT are expected
    to not have writeback caching enabled? 'cause there's no way they're
    issuing syncs themselves.

    So yeah, I'd agree that the loop code should be reworked a bit so that
    both the filebacked and aio methods call vfs_sync() when they see


    - z
    (Sorry, no real time to dig into this now. Lots more time in two months!)

     \ /
      Last update: 2012-04-20 18:01    [W:0.023 / U:28.068 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site