LWN: Comments on "Kernel prepatch 3.8-rc2"

3.8-rc1+ transparent-huge-page zero-page split bugons

Tara_Li — Thu, 03 Jan 2013 18:12:05 +0000

Yeah - if you can fairly reliably reproduce this - make the devs happy with one less heisenbug!

3.8-rc1+ transparent-huge-page zero-page split bugons

ebiederm — Thu, 03 Jan 2013 06:57:52 +0000

lkml does not require a subscription to post.

Sending an email with backtraces to the developers of of that part of the kernel should get your issue looked at and with a little luck resolved quickly.

3.8-rc1+ transparent-huge-page zero-page split bugons

Duncan — Thu, 03 Jan 2013 06:49:18 +0000

I've been seeing regular huge-page split kernel-bugons with 3.8-r1-g*, and don't see any fixes. For me, they seem to occur pretty regularly when I close my last firefox window.

I suspect it's the new transparent-huge-page zero-pages. Firefox apparently allocates some but never writes to them, then when it quits, I get the bugon apparently as the zero-huge-page is split back into its components to return to the pool. The code for splitting huge-pages apparently doesn't yet have an appropriate exception for the zero-huge-page split-and-return-to-pool case.

I just disabled transparent-huge-pages when I rebuilt for rc2. That should work around the problem for now, I hope.

I haven't bug-reported it yet. No lkm subscription so I usually file a bug on kernel bugzilla, but haven't on this one yet.