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    SubjectRe: [Bug #14141] order 2 page allocation failures in iwlagn
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    On Monday 12 October 2009, Mel Gorman wrote:
    > Maybe. Your commit id's are different to what I see. Maybe it's because
    > your tree has been shuffled around a bit

    No, the commit IDs should be identical. My tree is just plain mainline.

    Just to make sure... You did remove the "g" from the IDs, right?
    So v2.6.30-rc6-1103-gb1bc81a becomes 'b1bc81a' and if you do
    'git describe b1bc81a' you really should end up with the same IDs I have.

    > but after some digging around in this general area, I saw this patch
    >
    > 4752c93c30 iwlcore: Allow skb allocation from tasklet

    That is v2.6.30-rc6-773-g4752c93, which is part of the first wireless
    merge I tested and where I saw no issues. But see below.

    > This patch increases the number of GFP_ATOMIC allocations that can occur
    > by allocating GFP_ATOMIC in some cases and GFP_KERNEL in others.
    > Previously, only GFP_KERNEL was used and I didn't realise this
    > allocation method was so recent. Problems of this sort have cropped up
    > before and while there are later changes that suppress some of these
    > warnings, I believe this is a strong candidate for where the allocation
    > failures started appearing.
    >
    > > v2.6.30-rc6-1032-g7ba10a8 mac80211: fix transposed min/max CW values
    > > 1.13 -
    > > This is a bugfix for aa837ee1d from an earlier merge! Could this maybe

    There's a typo here. That ID should be: aa837e1d.

    > > influence the test results in between? There are various SKB related
    > > changes there, for example: dfbf97f3..e5b9215e.
    > > v2.6.30-rc6-1037-g2c5b9e5 wireless: libertas: fix unaligned accesses
    > > 1.12 +-
    > > v2.6.30-rc6-1044-g729e9c7 cfg80211: fix for duplicate userspace replies
    > > 1.10 +-
    > > v2.6.30-rc6-1075-gc587de0 iwlwifi: unify station management
    > > 1.9 ++-|+-
    > > v2.6.30-rc6-1076-gd14d444 iwl3945: port allow skb allocation in tasklet
    > > I thought this was a prime candidate, but as you can see
    > > several commits before failed too. Still worth looking at I think!
    >
    > Your commit IDs are different to what I see but it's the commit merge at
    > b1bc81a0ef86b86fa410dd303d84c8c7bd09a64d. I agree that the last commit
    > (d14d44407b9f06e3cf967fcef28ccb780caf0583) could make the problem worse
    > because it expands the use of GFP_ATOMIC for another driver.

    No, that was a mistake of mine. d14d444 is in a driver I don't even compile.
    The one you identified (which is the same change for iwlagn) is much more
    interesting.

    I really do think that v2.6.30-rc6-1032-g7ba10a8 could play a role here.
    That's a fix for v2.6.30-rc1-1131-gaa837e1. So that bug was introduced
    _before_ the merge 82d0481 and may thus well explain both the latencies I
    saw _and_ why that merge tested without problems. And that would also go a
    long way to explain my test results.
    So I'm going to retest 82d0481 with 7ba10a8 cherry-picked on top.

    > > BISECTION of akpm (mm) MERGE
    > > ----------------------------
    [...]
    > While I didn't spot anything too out of the ordinary here, they did
    > occur shortly after a number of other page allocator related patches.
    > One small thing I noticed there is that kswapd is getting woken up less
    > now than it did previously. Generally, I wouldn't have expected it to
    > make a difference but it's possible that kswapd is not being woken up to
    > reclaim at a higher order than it was previously. I have a patch for
    > this below. It'd be nice if you could apply it and see do fewer
    > allocation failures occur on current mainline.

    I'll give that patch a try and report back.


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