why is transparent hugepage disabled?
braveheartleo
Status: Interested
Joined: 23 Jan 2012
Posts: 43
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Hi,

Is there any reason why transparent hugepage has been disabled in liquorix? It used to be that this was enabled in the past.

:: Code ::
$ grep HUGEP /boot/config-3.18-9.dmz.1-liquorix-amd64
CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE=y
CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION=y
# CONFIG_TRANSPARENT_HUGEPAGE is not set

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damentz
Status: Assistant
Joined: 09 Sep 2008
Posts: 1122
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Hi braveheartleo,

I turned off transparent huge pages after reading this article: antirez.com/news/84

Nothing too scientific, but in testing, antirez found that transparent huge pages caused latency spikes in specific workloads. Since Liquorix's focus is on low latency usage, I disabled this option.

And in the comments, someone links to a CouchBase blog that discovered the same thing: blog.couchbase.com/often-overlooked-linux-os-tweaks

General consensus when doing real work, THP improves performance by merging smaller allocations, which ultimately increases latency of certain operations that require small pages, some that might impact the responsiveness of your desktop / laptop.
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braveheartleo
Status: Interested
Joined: 23 Jan 2012
Posts: 43
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Hi damentz,

Thanks for those links. I'll be sure to read them up and take a second look at THP.
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