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Description of problem:

QEMU will only use transparent huge pages if it's enabled system wide. This happens because QEMU doesn't call MADV_HUGEPAGE for ram allocations.


Version-Release number of selected component (if applicable): QEMU 1.2 and earlier


How reproducible:


Steps to Reproduce:
1. Enable THP only for MADV_HUGEPAGE:

  # echo madvise > /sys/kernel/mm/transparent_hugepage/enabled

2. Start a QEMU process (a reasonable amount of RAM, say 1G, should be better)

3. Check QEMU's huge page usage

  # grep AnonHugePages /proc/qemu-pid/smaps
  
Actual results:

All lines is:

AnonHugePages:         0 kB

Meaning that huge pages are not used.

Expected results:

Some lines should have > 0 results, eg:

AnonHugePages:    276480 kB

Additional info:

Posted patch upstream:

https://lists.gnu.org/archive/html/qemu-devel/2012-10/msg01012.html

Patch merged on qemu upstream, commit: ad0b5321f1f797274603ebbe20108b0750baee94

Verified on qemu-kvm-rhev-1.5.3-31.el7.x86_64:


[root@localhost ~]# grep AnonHugePages /proc/21914/smaps
AnonHugePages:         0 kB
AnonHugePages:         0 kB
AnonHugePages:    530432 kB
AnonHugePages:         0 kB
...

This request was resolved in Red Hat Enterprise Linux 7.0.

Contact your manager or support representative in case you have further questions about the request.