lkml.org 
[lkml]   [2004]   [Nov]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: page fault scalability patch V11 [0/7]: overview
    Christoph Lameter wrote:
    > On Sat, 20 Nov 2004, Nick Piggin wrote:
    >
    >
    >>I think this sounds like it might be a good idea. I prefer it to having
    >>the unbounded error of sloppy rss (as improbable as it may be in practice).
    >
    >
    > It may also be faster since the processors can have exclusive cache lines.
    >

    Yep.

    > This means we need to move rss into the task struct. But how does one get
    > from mm struct to task struct? current is likely available most of
    > the time. Is that always the case?
    >

    It is available everywhere that mm_struct is, I guess. So yes, I
    think `current` should be OK.

    >
    >>The per thread rss may wrap (maybe not 64-bit counters), but even so,
    >>the summation over all threads should still end up being correct I
    >>think.
    >
    >
    > Note though that the mmap_sem is no protection. It is a read lock and may
    > be held by multiple processes while incrementing and decrementing rss.
    > This is likely reducing the number of collisions significantly but it wont
    > be a guarantee like locking or atomic ops.
    >

    Yeah the read lock won't do anything to serialise it. I think what Linus
    is saying is that we _don't care_ most of the time (because the error will
    be bounded). But if it happened that we really do care anywhere, then the
    write lock should be sufficient.
    -
    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 14:08    [W:2.864 / U:0.004 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site