lkml.org 
[lkml]   [2001]   [Oct]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: Pls apply this spinlock patch to the kernel

    On Mon, 29 Oct 2001, Juergen Doelle wrote:
    >
    > I had created a patch for improving the spinlock behavior on IA32 SMP
    > systems for file system work load created with dbench
    > (ftp://samba.org/pub/tridge/dbench). The work load is a mix of create,
    > delete, write, and read operations executed from a scalable number of
    > clients. It is mainly handled in buffer cache.

    Fair enough. However, I wonder why you didn't just use the existing
    (unaligned) types, and then on a lock-by-lock basis just mark them
    aligned. That implies no code-changes.

    Something like this should do it:

    .. regular "spinlock_t" type

    #define cachealign \
    __attribute__((section("aligned"),__aligned__(SMP_CACHELINE_SIZE)))

    (use a separate section so that subsequent data structures are also
    guaranteed to be aligned - otherwise you might get false sharing from
    non-aligned data structures that follow this one).

    Eh?

    Yes, we already try to do something like this, but due to the false
    sharing with other stuff it doesn't _guarantee_ an exclusive cacheline.
    Sometimes that is what you want (ie once you get the lock, it _can_ be
    advantageous to have the hottest data structure associated with the lock
    be in the same cacheline)

    Linus

    -
    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 13:11    [W:2.932 / U:0.796 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site