3.1 HugeTLB setup regression?

[Josh Boyer <jwboyer@redhat.com>]

Hi All,

We've had a report[1] of an existing hugetlb setup that worked in Fedora
14 (2.6.35.x) and Fedora 15 (2.6.38-3.0?) that no longer works when
using the 3.1.x kernel.  The details in the bug are somewhat sparse on
exactly which kernel version(s) worked and when it stopped working, but
I thought I'd include some of the relevant comments to see if anyone can
think of why this would stop working:

1. Allocate large pages through sysctl.conf, with the following:
# Enable large page memory
kernel.shmmax=25769803776
vm.nr_hugepages=10752
vm.hugetlb_shm_group=1001

There is 24 GB of memory on the server, and I'm allocating 21GB (I have
done
this on Fedora 14 and 15 with no issues.

2. Set /etc/security/limits.conf to allow for memlock to be unlimited
for the
user.
3. Create the hugetlb group, and put the users in that group.
4. Turn off transparent huge pages through a boot parameter
transparent_hugepage=never
5. Run the following java command:

java -XX:+UseLargePages -Xms8g -Xmx8g -version

Actual results:

java -XX:+UseLargePages -Xms8g -Xmx8g -version
OpenJDK 64-Bit Server VM warning: Failed to reserve shared memory (errno
= 28).
java version "1.6.0_22"
OpenJDK Runtime Environment (IcedTea6 1.10.4)
(fedora-60.1.10.4.fc16-x86_64)

Apparently dropping it to use 7G works though:

java -XX:+UseLargePages -Xms7g -Xmx7g -version
java version "1.6.0_22"
OpenJDK Runtime Environment (IcedTea6 1.10.4)
(fedora-60.1.10.4.fc16-x86_64)
OpenJDK 64-Bit Server VM (build 20.0-b11, mixed mode)

I'd appreciate any thoughts or further questions to ask for follow up.

josh

[1] https://bugzilla.redhat.com/show_bug.cgi?id=761262

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