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Date: Tue, 10 Sep 2013 12:50:23 +0900
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Subject: /proc/sys/vm/zone_reclaim_mode
From: Takenori Sato <tsato@cloudian.com>
To: "user@cassandra.apache.org" <user@cassandra.apache.org>
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Hi,

I am investigating NUMA issues.

I have been aware that bin/cassandra tries to use interleave all policy if
available.

https://issues.apache.org/jira/browse/CASSANDRA-2594
https://issues.apache.org/jira/browse/CASSANDRA-3245

So what about /proc/sys/vm/zone_reclaim_mode? Any recommendations? I didn't
find any in respect to Cassandra.

By default on Linux NUMA machine, this is set 1 that tries to reclaim some
pages in a zone rather than acquiring others from the other zones.

Explicitly disabling this sounds better.

"It may be beneficial to switch off zone reclaim if the system is used for
a file server and all of memory should be used for caching files from disk.
In that case the caching effect is more important than data locality."
https://www.kernel.org/doc/Documentation/sysctl/vm.txt

Thanks!
Takenori

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<div dir=3D"ltr">Hi,<div><br></div><div style>I am investigating NUMA issue=
s.</div><div style><br></div><div style>I have been aware that bin/cassandr=
a tries to use interleave all policy if available.</div><div style><br></di=
v>
<div style><div style=3D"color:rgb(0,0,0);font-family:Arial,Helvetica,sans-=
serif;font-size:12px;line-height:21px"><a href=3D"https://issues.apache.org=
/jira/browse/CASSANDRA-2594" style=3D"color:rgb(68,68,68);outline:none;text=
-decoration:none!important">https://issues.apache.org/jira/browse/CASSANDRA=
-2594</a></div>
<div style=3D"color:rgb(0,0,0);font-family:Arial,Helvetica,sans-serif;font-=
size:12px;line-height:21px"><a href=3D"https://issues.apache.org/jira/brows=
e/CASSANDRA-3245" style=3D"color:rgb(68,68,68);text-decoration:none;outline=
:none">https://issues.apache.org/jira/browse/CASSANDRA-3245</a></div>
</div><div style><br></div><div style>So what about=A0/proc/sys/vm/zone_rec=
laim_mode? Any recommendations? I didn&#39;t find any in respect to Cassand=
ra.</div><div style><br></div><div style>By default on Linux NUMA machine, =
this is set 1 that tries to reclaim some pages in a zone rather than acquir=
ing others from the other zones.</div>
<div style><br></div><div style>Explicitly disabling this sounds better.<br=
></div><div style><br></div><div style>&quot;<span style=3D"color:rgb(0,0,0=
);white-space:pre-wrap">It may be beneficial to switch off zone reclaim if =
the system is </span><span style=3D"color:rgb(0,0,0);white-space:pre-wrap">=
used for a file server and all of memory should be used for caching files <=
/span><span style=3D"color:rgb(0,0,0);white-space:pre-wrap">from disk. In t=
hat case the caching effect is more important than=A0</span><span style=3D"=
color:rgb(0,0,0);white-space:pre-wrap">data locality.</span>&quot;</div>
<div style><a href=3D"https://www.kernel.org/doc/Documentation/sysctl/vm.tx=
t">https://www.kernel.org/doc/Documentation/sysctl/vm.txt</a><br></div><div=
 style><br></div><div style>Thanks!</div><div style>Takenori</div></div>

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