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Old 03-14-2018, 02:13 AM   #1
Darth Vader
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Registered: May 2008
Location: Romania
Distribution: DARKSTAR Linux 2008.1
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Kernel: there is a reasonable explanation why the "typical Linux user" needs Transparent Huge Pages? Memory consumption: 42GB vs 5.7GB


From long time I have an issue. And that's really a long time.

The issue is the epic huge memory consumption in computers which I use for work. You read right, I can hit 42GB memory consumption in a day of work. That's 32GB real memory, the rest is SWAP, with all the fun.

And I have a very good excuse: very bad habits, as in tons of Firefox and Chromium pages open, LAMP stack running in background dozens of local sites, REDIS and so on...

Then, somewhen a month ago, I had the bad idea to look in the REDIS logs. Hundred times, they said so:
Quote:
WARNING you have Transparent Huge Pages (THP) support enabled in your kernel. This will create latency and memory usage issues with Redis. To fix this issue run the command 'echo never > /sys/kernel/mm/transparent_hugepage/enabled' as root, and add it to your /etc/rc.local in order to retain the setting after a reboot. Redis must be restarted after
THP is disabled.
I had then the stupid idea to follow that recommendation, and I added into rc.local
Code:
echo never > /sys/kernel/mm/transparent_hugepage/enabled
For my surprise, the memory consumption never then passed the 5.77GB. Reasonable for a 32GB system, right?

After all, I think that's much more reasonable than 42GB, in my humble opinion...

Then, I tried the same thing in more lightly used computers. That's "only" some hundreds pages opened in Firefox, in my vision.

For my surprise, computers with 8GB which easily hit the SWAP while I walked in a news site (and opened about hundred tabs in Firefox or Chrome), now not hit 3GB memory consumption.

In the final, I arrived to conclusion that THIS thing: Transparent Huge Pages enabled in the kernels, interacts freaking badly with Firefox, Chromium, LAMP stack and REDIS habits.

Then, dear Slackware Team, permit me to ask you:

FOR WHAT THE HECK are good those Transparent Huge Pages, excluding the wasting the users computers memory, thing which they do perfectly?

Last edited by Darth Vader; 03-14-2018 at 01:43 PM.
 
Old 03-14-2018, 02:24 AM   #2
volkerdi
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Thanks for pointing that out. I'll add CONFIG_TRANSPARENT_HUGEPAGE_MADVISE=y.
 
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Old 03-14-2018, 02:32 AM   #3
Darth Vader
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Original Poster
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Thanks, Patrick!

I can consider then this thread solved.

Last edited by Darth Vader; 03-14-2018 at 03:42 PM.
 
Old 03-15-2018, 12:13 AM   #4
Richard Cranium
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Registered: Apr 2009
Location: Carrollton, Texas
Distribution: Slackware64 14.2
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Quote:
Originally Posted by Darth Vader View Post
FOR WHAT THE HECK are good those Transparent Huge Pages, excluding the wasting the users computers memory, thing which they do perfectly?
/usr/src/linux-4.4.118/Documentation/vm/hugetlbpage.txt contains any answers you'd want.

I don't remember making any changes, but on all of my Slackware64 systems:
Code:
130 ✗ cranium@cranium ~ $ cat /sys/kernel/mm/transparent_hugepage/enabled 
[always] madvise never
The maximum amount of physical RAM on any of my machines is 16GB.

(I've certainly seen the same messages from Redis docker images when they boot up at work, so I've seen the same thing there and turned off THP in those cases.)
 
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Old 03-15-2018, 09:45 PM   #5
orbea
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Registered: Feb 2015
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I built 4.14.26 here with CONFIG_TRANSPARENT_HUGEPAGE_MADVISE=y and it feels rather strange that firefox is no longer trying to use all my ram.
 
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Old 03-16-2018, 02:50 AM   #6
chrisretusn
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Well I was gonna wait until tomorrow or the next to upgrade my kernel to 4.14.26, I will upgrade as soon as my local repository syncs at a 1600 my time.
 
  


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