lkml.org 
[lkml]   [2002]   [Jan]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [2.4.17/18pre] VM and swap - it's really unusable
    On Fri, Jan 04, 2002 at 03:24:09PM +0100, Stephan von Krawczynski wrote:
    > On Fri, 4 Jan 2002 15:14:38 +0100
    > Andrea Arcangeli <andrea@suse.de> wrote:
    >
    > > On Fri, Jan 04, 2002 at 01:33:21PM +0100, Stephan von Krawczynski wrote:
    > > > On Thu, 03 Jan 2002 20:14:42 -0600
    > > > "M.H.VanLeeuwen" <vanl@megsinet.net> wrote:
    > > >
    > > > And there is another difference here:
    > > >
    > > > + if (max_mapped <= 0 && nr_pages > 0)
    > > > + swap_out(priority, gfp_mask, classzone);
    > > > +
    > > >
    > > > It sounds reasonable _not_ to swap in case of success (nr_pages == 0).
    > > > To me this looks pretty interesting. Is something like this already in -aa?
    > > > This patch may be worth applying in 2.4. It is small and looks like the
    > right> > thing to do.
    > >
    > > -aa swapout as soon as max_mapped hits zero. So it basically does it
    > > internally (i.e. way more times) and so it will most certainly be able
    > > to sustain an higher swap transfer rate. You can check with the mtest01
    > > -w test from ltp.
    >
    > Hm, but do you think this is really good in overall performance, especially the
    > frequent cases where no swap should be needed _at all_ to do a successful
    > shrinking? And - as can be viewed in Martins tests - if you have no swap at

    the common case is that max_mapped doesn't reach zero, so either ways
    (mainline or -aa) it's the same (i.e. no special exit path).

    > all, you seem to trigger OOM earlier through the short path exit in shrink,
    > which is a obvious nono. I would state it wrong to fix the oom-killer for this
    > case, because it should not be reached at all.

    Correct. Incidentally swap or no swap doesn't make any difference on the
    exit-path of shrink_cache in -aa (furthmore if swap is full or if everything is
    unfreeable I stop wasting an huge amount of time on the swap_out path at the
    first failure, this allows graceful oom handling or it would nearly deadlock
    there trying tp swap unfreeable stuff at every max_mapped reached). In -aa
    max_mapped doesn't influcence in any way the exit path of shrink_cache.
    max_mapped only controls the swapout-frequency. See:

    if (!page->mapping || page_count(page) > 1) {
    spin_unlock(&pagecache_lock);
    UnlockPage(page);
    page_mapped:
    if (--max_mapped < 0) {
    spin_unlock(&pagemap_lru_lock);

    shrink_dcache_memory(vm_scan_ratio, gfp_mask);
    shrink_icache_memory(vm_scan_ratio, gfp_mask);
    #ifdef CONFIG_QUOTA
    shrink_dqcache_memory(vm_scan_ratio, gfp_mask);
    #endif

    if (!*failed_swapout)
    *failed_swapout = !swap_out(classzone);

    max_mapped = orig_max_mapped;
    spin_lock(&pagemap_lru_lock);
    }
    continue;

    }

    So it should work just fine as far I can tell.

    Andrea
    -
    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 13:15    [W:0.035 / U:29.984 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site