On Fri, 17 Feb 2012 23:14:01 -0800 (PST)
Hugh Dickins [off-list ref] wrote:

On Sat, 18 Feb 2012, Konstantin Khlebnikov wrote:

quoted

Hugh Dickins wrote:

quoted

On Thu, 16 Feb 2012, Hugh Dickins wrote:

quoted

Yours are not the only patches I was testing in that tree, I tried to
gather several other series which I should be reviewing if I ever have
time: Kamezawa-san's page cgroup diet 6, Xiao Guangrong's 4 prio_tree
cleanups, your 3 radix_tree changes, your 6 shmem changes, your 4 memcg
miscellaneous, and then your 15 books.

The tree before your final 15 did well under pressure, until I tried to
rmdir one of the cgroups afterwards: then it crashed nastily, I'll have
to bisect into that, probably either Kamezawa's or your memcg changes.

So far I haven't succeeded in reproducing that at all: it was real,
but obviously harder to get than I assumed - indeed, no good reason
to associate it with any of those patches, might even be in 3.3-rc.

It did involve a NULL pointer dereference in mem_cgroup_page_lruvec(),
somewhere below compact_zone() - but repercussions were causing the
stacktrace to scroll offscreen, so I didn't get good details.

There some stupid bugs in my v1 patchset, it shouldn't works at all.
I did not expect that someone will try to use it. I sent it just to discuss.

Yes, but as I said, that bug appeared before I put your patchset (the 15) on.

Hm, NULL pointer dereference in mem_cgroup_page_lruvec() via comaction tend to
mean pc->mem_cgroup was NULL... 

IIUC,

- compaction get pages from LRU list and isolate/migrate them. So, When pages
  on LRU were migrated by compact_zone(), pc->mem_cgroup never be NULL..
- All newly allocated pages for migration will be reset by mem_cgroup_reset_owner().

Hm, something unexpected happens..

Regards,
-Kame
 

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