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Nexx
PostPosted: Mon Mar 30, 2009 4:01 am 
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Just a quick query about my Linode 360's RAM ^^

I've noticed that "free -m" only reports 349MB of memory being available:
Code:
             total       used       free     shared    buffers     cached
Mem:           349        275         73          0        110        133
-/+ buffers/cache:         31        317
Swap:          255          0        255


Yet the kernel clearly reports 360 as being available:
Code:
0MB HIGHMEM available.
360MB LOWMEM available.


Other people who have posted stats from "free -m" show the full 360MB being available:
http://www.linode.com/forums/viewtopic.php?p=19760#19760
Code:
             total       used       free     shared    buffers     cached
Mem:           360        338         21          0          6        246
-/+ buffers/cache:         85        274
Swap:          255          0        255


Is this a bug with the Xen stack on newark41 or is it due to the kernel I'm using (2.6.28.3-linode17)?

Just curious ;)
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mikeage
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PostPosted: Mon Mar 30, 2009 9:20 am 
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Hrmm... I just noticed the same thing, although on a different kernel (and different host):
Code:
mikeage@linode ~$ uname -a
Linux linode 2.6.27.4-x86_64-linode3 #1 SMP Thu Nov 6 09:32:36 EST 2008 x86_64 GNU/Linux
mikeage@linode ~$ free -m
             total       used       free     shared    buffers     cached
Mem:           344        340          4          0          2        136
-/+ buffers/cache:        201        142
Swap:          511        257        254
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melz
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PostPosted: Mon Mar 30, 2009 9:37 am 
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It's the kernel you're using. I tried the newer kernels and had that issue so I switched back to the stable one - that fixed the problem.
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oliver
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PostPosted: Mon Mar 30, 2009 9:38 am 
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AOL: derole
that was discussed before, search the forum for more information.
i believe it's a XEN vs. UML issue.
i'm on a XEN host and free reports the full 360.
my output looks like this:

Code:
$ uname -a                                                                          
Linux li19-162 2.6.18.8-linode16 #1 SMP Mon Jan 12 09:50:18 EST 2009 i686 i686 i386 GNU/Linux       
$ free -m                                                                           
             total       used       free     shared    buffers     cached                           
Mem:           360        334         25          0         85        127                           
-/+ buffers/cache:        121        238                                                            
Swap:          255          6        249                                                            
$
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mikeage
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PostPosted: Mon Mar 30, 2009 10:20 am 
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I'm on a XEN host too
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dcelasun
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PostPosted: Mon Mar 30, 2009 11:45 am 
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The problem is NOT UML v.s XEN. I'm on a XEN host as well and here's my output:

Code:
             total       used       free     shared    buffers     cached
Mem:           349        302         47          0        103        124
-/+ buffers/cache:         74        274
Swap:          255          6        249
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Xan
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PostPosted: Mon Mar 30, 2009 12:12 pm 
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For what it's worth, I see the full amount of memory on a Xen node running the "latest" kernel (2.6.18.8-linode16), as well as on one using PV to run the stock Lenny kernel 2.6.26-1-xen-686.
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sweh
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PostPosted: Mon Mar 30, 2009 6:47 pm 
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Huh, 349M here on my Xen based linode.

Code:
% free -m
             total       used       free     shared    buffers     cached
Mem:           349        276         72          0         19        214
-/+ buffers/cache:         42        306
Swap:          256          4        252

% uname -sr
Linux 2.6.28.3-linode17

_________________
Rgds
Stephen
(Linux user since kernel version 0.11)
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hybinet
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PostPosted: Tue Mar 31, 2009 12:03 am 
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If you're on Xen and you use Linode-provided kernels newer than the "latest stable" 2.6.18, you get only 349M of RAM.
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mikeage
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PostPosted: Tue Mar 31, 2009 12:06 am 
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Any idea why everyone else is seeing 349 and I only get 344?
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dcelasun
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PostPosted: Tue Mar 31, 2009 12:56 am 
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hybinet wrote:
If you're on Xen and you use Linode-provided kernels newer than the "latest stable" 2.6.18, you get only 349M of RAM.
And the reason for that is?
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mwalling
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PostPosted: Tue Mar 31, 2009 7:44 am 
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Latest Stable is a kernel from xensource, where the newer ones are from kernel.org with pv_ops
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Nexx
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PostPosted: Wed Apr 01, 2009 10:24 am 
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Thanks everyone for the input, I'll give 2.6.18 a go next time I reboot my Linode.

mikeage wrote:
Any idea why everyone else is seeing 349 and I only get 344?
The only difference I've noticed so far is that you're running a 64bit system, everyone else in the thread seems to be running 32bit instead.
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Stever
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PostPosted: Wed Apr 01, 2009 11:26 am 
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I noticed this back when I was first switching to the pv_ops kernels, and I think I convinced myself that you really have the same memory in either case. In my testing I looked at free immediately after booting with the different kernels and got:
Code:
[boot xensource]
$ uname -a
Linux ???.com 2.6.18.8-x86_64-linode1 #1 SMP Thu Apr 10 11:20:13 EDT 2008 x86_64 Intel(R) Xeon(R) CPU L5420 @ 2.50GHz GenuineIntel GNU/Linux
$ free -m
             total       used       free     shared    buffers     cached
Mem:           360         72        288          0          2         31
-/+ buffers/cache:         38        322
Swap:          719          0        719

[reboot pv_ops]
$ uname -a
Linux ???.com 2.6.27.4-x86_64-linode3 #1 SMP Thu Nov 6 09:32:36 EST 2008 x86_64 Intel(R) Xeon(R) CPU L5420 @ 2.50GHz GenuineIntel GNU/Linux
$ free -m
             total       used       free     shared    buffers     cached
Mem:           344         61        282          0          2         32
-/+ buffers/cache:         27        317
Swap:          719          0        719

It looks to me like the "total" is lower as everyone is complaining about, but also the "used" is lower to almost the same extent, resulting in very similar "free" for each kernel.
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Nexx
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PostPosted: Wed Apr 01, 2009 6:41 pm 
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Just a little update to this. I just rebooted my Linode into the 2.6.18.8-linode16 kernel. "free -m" now reports:
Code:
             total       used       free     shared    buffers     cached
Mem:           360         45        314          0          2         17
-/+ buffers/cache:         25        334
Swap:          255          0        255


But, interestingly, the amount of RAM reported by the kernel boot messages has increased too:
Code:
2.6.18.8-linode16 kernel:
0MB HIGHMEM available.
368MB LOWMEM available.

2.6.28.3-linode17:
0MB HIGHMEM available.
360MB LOWMEM available.


Stever wrote:
It looks to me like the "total" is lower as everyone is complaining about, but also the "used" is lower to almost the same extent, resulting in very similar "free" for each kernel.

Interesting theory, but my fresh-boot used memory is the same on both kernels (25MB).

I didn't mean to sound like I was complaining by the way, it was just an observation. I'm extremely happy with my Linode, both the service and support are above and beyond anything I've experienced before ^^.

Addition:
My mistake, you're correct Stever, my clean-boot with 2.6.28.3-linode17 shows the used memory at 15MB, not 25MB. So it would seem that although the official xensource kernel shows all the RAM in "free -m", it's still allocated to something, somewhere.
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