lkml.org 
[lkml]   [2004]   [Mar]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: 2.4.23aa2 (bugfixes and important VM improvements for the high end)
    Andrea Arcangeli wrote:
    > > Can you use a read-write lock, so that userspace copies only need to
    > > take the lock for reading? That doesn't eliminate cacheline bouncing
    > > but does eliminate the serialisation.
    >
    > normally the bouncing would be the only overhead, but here I also think
    > the serialization is a significant factor of the contention because the
    > critical section is taking lots of time. So I would expect some
    > improvement by using a read/write lock.

    For something as significant as user<->kernel data transfers, it might
    be worth eliminating the bouncing as well - by using per-CPU * per-mm
    spinlocks.

    User<->kernel data transfers would take the appropriate per-CPU lock
    for the current mm, and not take page_table_lock. Everything that
    normally takes page_table_lock would, and also take all of the per-CPU locks.

    That does require a set of per-CPU spinlocks to be allocated whenever
    a new mm is allocated (although the sets could be cached so it needn't
    be slow).

    -- Jamie
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2005-03-22 14:01    [W:4.891 / U:0.100 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site