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Old 08-04-2008, 10:44 PM
Account for Debian group mail
 
Default swappiness of 2.6 kernel

Hello,

Has anyone played with the swappiness settings of the 2.6 kernel? It looks
like the default is set at 60. I was thinking on this new machine I put
together with 4 gigs of ram that I might bump this number up a little,
maybe like 80.


Any thoughts?

Thanks,

Ken


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Old 08-05-2008, 05:27 AM
Chris Burkhardt
 
Default swappiness of 2.6 kernel

Account for Debian group mail wrote:


Hello,

Has anyone played with the swappiness settings of the 2.6 kernel? It
looks like the default is set at 60. I was thinking on this new machine
I put together with 4 gigs of ram that I might bump this number up a
little, maybe like 80.


Any thoughts?


I've never experimented, but it seems Andrew Morton sets it at 100:
http://kerneltrap.org/node/3000


- Chris


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Old 08-05-2008, 06:05 AM
Sven Joachim
 
Default swappiness of 2.6 kernel

On 2008-08-05 07:27 +0200, Chris Burkhardt wrote:

> Account for Debian group mail wrote:
>>
>> Hello,
>>
>> Has anyone played with the swappiness settings of the 2.6 kernel? It
>> looks like the default is set at 60. I was thinking on this new
>> machine I put together with 4 gigs of ram that I might bump this
>> number up a little, maybe like 80.
>>
>> Any thoughts?
>
> I've never experimented, but it seems Andrew Morton sets it at 100:
> http://kerneltrap.org/node/3000

That thread is rather old, but from reading it I'd be attempted to
_reduce_ rather than increase the swappiness. It's annoying enough that
the disk cache is blown away by watching a DVD movie, but if you
increase swappiness your applications will be swapped out as well,
giving sluggish response when you return to them.

Sven


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Old 08-05-2008, 07:28 AM
"thveillon.debian"
 
Default swappiness of 2.6 kernel

Sven Joachim a écrit :

On 2008-08-05 07:27 +0200, Chris Burkhardt wrote:


Account for Debian group mail wrote:

Hello,

Has anyone played with the swappiness settings of the 2.6 kernel? It
looks like the default is set at 60. I was thinking on this new
machine I put together with 4 gigs of ram that I might bump this
number up a little, maybe like 80.

Any thoughts?

I've never experimented, but it seems Andrew Morton sets it at 100:
http://kerneltrap.org/node/3000


That thread is rather old, but from reading it I'd be attempted to
_reduce_ rather than increase the swappiness. It's annoying enough that
the disk cache is blown away by watching a DVD movie, but if you
increase swappiness your applications will be swapped out as well,
giving sluggish response when you return to them.

Sven


On a Desktop workstation (multimedia edit, 4Gb ram, timer freq being set
@ 1000HZ) I've been using 20 for a long time, no problem whatsoever and
no swapping at all.
From my understanding for a server you need something closer or equal
to 100, for a workstation anything between 0 and 20 will do, anyway if
swapping must occur it will and the settings will be overridden, but no
"provisional" swapping (that's my word, not sure it makes sens...) will
occur, resulting in a more responsive experience especially when coming
back to an application left idle for a while.


That's my experience, and therefore my 2 cents...

Tom


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Old 08-05-2008, 01:30 PM
Account for Debian group mail
 
Default swappiness of 2.6 kernel

On Tue, 5 Aug 2008, thveillon.debian wrote:

On a Desktop workstation (multimedia edit, 4Gb ram, timer freq being set @
1000HZ) I've been using 20 for a long time, no problem whatsoever and no
swapping at all.
From my understanding for a server you need something closer or equal to 100,
for a workstation anything between 0 and 20 will do, anyway if swapping must
occur it will and the settings will be overridden, but no "provisional"
swapping (that's my word, not sure it makes sens...) will occur, resulting in
a more responsive experience especially when coming back to an application
left idle for a while.


That's my experience, and therefore my 2 cents...

Tom


Tom,

That is about what I was thinking. Since this is a mail server it would
seem like a disk cache is not a big deal. This being all the disk access
is mostly mail files coming in. But you do need a bunch free memory for
programs, very memory hungry program, involved in processing incoming
mail.


So far the 80 setting has freed up some free memory for use. What I can't
understand is why this 76k of swap memory keeps getting used. I'll clear
it out and then couple of hours later there it is again. Anyway here is a
snap shot of the current top:


Ken

top - 06:27:16 up 1 day, 20:15, 4 users, load average: 1.22, 1.03, 0.90
Tasks: 118 total, 1 running, 117 sleeping, 0 stopped, 0 zombie
Cpu0 : 0.7%us, 1.0%sy, 6.3%ni, 92.1%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu1 : 1.6%us, 3.3%sy, 24.3%ni, 57.2%id, 12.8%wa, 0.3%hi, 0.3%si, 0.0%st
Mem: 3927348k total, 3520456k used, 406892k free, 277516k buffers
Swap: 5076532k total, 76k used, 5076456k free, 2126116k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
28287 clamav 20 0 437m 260m 1232 S 0 6.8 14:15.51 clamav-milter
28066 clamav 20 0 102m 86m 720 S 0 2.3 0:31.62 clamd
20863 root 37 17 106m 74m 2432 S 13 1.9 0:04.76 spamd
21252 smithj 37 17 103m 71m 2408 S 17 1.9 0:01.86 spamd
21395 root 37 17 102m 70m 2320 S 0 1.8 0:00.32 spamd
4970 root 37 17 100m 68m 2180 S 0 1.8 1:28.18 spamd
2505 root 20 0 246m 68m 804 S 1 1.8 14:30.21 milter-greylist
2500 dcc 20 0 67132 9280 1288 S 0 0.2 1:08.84 dccifd
442 root 20 0 39296 4180 1984 S 0 0.1 0:00.00 sendmail-mta
28692 root 20 0 39272 4124 1928 S 0 0.1 0:00.00 sendmail-mta
865 root 20 0 39272 4092 1928 S 0 0.1 0:00.00 sendmail-mta
11537 root 20 0 39272 4092 1928 S 0 0.1 0:00.00 sendmail-mta
25395 root 20 0 39272 4092 1928 S 0 0.1 0:00.00 sendmail-mta
19006 root 20 0 39272 4080 1940 S 0 0.1 0:00.00 sendmail-mta
20825 root 20 0 39272 4080 1928 S 0 0.1 0:00.00 sendmail-mta
21420 root 20 0 39272 4072 1944 S 0 0.1 0:00.00 sendmail-mta
19220 root 20 0 39004 4008 1876 S 0 0.1 0:00.00 sendmail-mta

etc.....


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Old 08-09-2008, 09:13 PM
Paul Johnson
 
Default swappiness of 2.6 kernel

On Tue, 2008-08-05 at 08:28 +0100, thveillon.debian wrote:

> On a Desktop workstation (multimedia edit, 4Gb ram, timer freq being set
> @ 1000HZ) I've been using 20 for a long time, no problem whatsoever and
> no swapping at all.

How sure are you on that? I've 2GB of RAM¹ and eventually something
sitting in memory that hasn't done anything in a long time will get
swapped out as a pre-emptive measure to keep more RAM available for disk
cache and other programs.

¹ I'm kind of curious where Tom got gigabits of RAM. )

--
Paul Johnson
baloo@ursine.ca
 
Old 08-10-2008, 07:35 PM
"thveillon.debian"
 
Default swappiness of 2.6 kernel

Paul Johnson wrote :

On Tue, 2008-08-05 at 08:28 +0100, thveillon.debian wrote:

On a Desktop workstation (multimedia edit, 4Gb ram, timer freq being set
@ 1000HZ) I've been using 20 for a long time, no problem whatsoever and
no swapping at all.


How sure are you on that? I've 2GB of RAM¹ and eventually something
sitting in memory that hasn't done anything in a long time will get
swapped out as a pre-emptive measure to keep more RAM available for disk
cache and other programs.

¹ I'm kind of curious where Tom got gigabits of RAM. )



I'm always getting confused between the French Octets, Bit, and the
English Bytes and such, so I guess I should have said 4GB ;-) ?


I don't keep a close eyes on my swap, but every time I look at it it's
not used at all. I guess it depends on the type of use and the apps
you're running. But from what I read on the subject it seems that
swapping may occur no matter what settings are used for the swappiness,
even 0, which is good if RAM is getting scarce...


Tom


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