[gke] UBUNTU: SAUCE: use CONFIG_TRANSPARENT_HUGEPAGE_MADVISE=y as default
BugLink: https://bugs.launchpad.net/bugs/1703742
The current configuration is set to always use transparent hugepages
by default. There exists plenty of anecdotal evidence that this is
less than perfect a choice and in some scenarios it leads to some
performance issues.
My own investigations with stress-ng stream and malloc tests show that
the current default impacts performance. I ran various test scenarios
on different MADVISE configurations, each result below is based on
the average of 5 runs on an i7-3770 CPU @ 3.4GHz with 8GB memory,
8MB L3 cache, 256K L2 cache, 32K/32K L1 cache.
All the above results are from an average of 5 rounds of tests.
malloc allocation stressor:
malloc always madvise
size (MB) ops/sec ops/sec
32 1254.43 2422.49
64 2100.36 4300.28
128 3768.57 7215.38
256 7940.73 14893.85
512 17618.62 26861.29
1024 32777.17 48029.37
Clearly madvise is more performent.
stream bandwidth/compute stressor:
stream always madvise
NOHUGEPAGE
size (MB) MB/sec MB/sec
1 17713.54 18439.69
2 12460.34 13015.46
4 12195.81 12694.51
8 12085.11 12674.26
16 12054.09 12649.00
32 12082.42 12409.65
64 12262.88 12084.85
128 12235.25 11788.49
256 11808.69 11283.69
512 11970.01 12434.82
For small allocations, always is less performant. Large
allocations can enable the more performant transparent
huge pages with madvise(2) if we disable always as default.
Other stress-ng memory allocation/writing/freeing and madvise
operations showed little significant differences.
I have also experimented with boot testing Ubuntu with kernels
configured with different MADVISE configs and found there is
little noticeable difference in performance, so I believe that
there is little scope for any kitten killer performance regressions
with this change.
This change will by default not use transparent huge pages unless
madvise(2) is used to instruct the kernel to do so on a memory
mapping. According to the madvise(2) manual, this only takes
effect on private anonymous mappings with MADV_HUGEPAGE.
Signed-off-by: Colin Ian King <email address hidden>
Signed-off-by: Seth Forshee <email address hidden>
Signed-off-by: Kamal Mostafa <email address hidden>
Acked-by: Kleber Sacilotto de Souza <email address hidden>
Acked-by: Marcelo Henrique Cerri <email address hidden>
