[CentOS] page allocation failure. order:0, mode:0x50

Just because I've been pulling my hair out for over a month about this
problem, I'd like to get it into the archives.

When copying large files (multigigabyte) on a CentOS 4.4 4GB Xeon
(running 32 bit) server (2.6.9-42.0.3.ELsmp), I was getting:

page allocation failure. order:0, mode:0x50

(snip lines and lines of debug output)


This was accompanied by a huge swapout storm that brought the system to
a near standstill.

Also, it could trigger OOM-Killer activity.

Setting /proc/sys/vm/lower_zone_protection to 150 seems to prevent the
problem. (It's not been long enough that I'm *certain* that it's fixed
but it seems to be.)

The upstream bug report is here:

https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=149088

Hope this helps someone someday, because I had a heck of a time finding
an answer.

-Steve Bergman