Is kswapd working right?

Is kswapd working right?

[mario camuñas]

Hello:

  Our scenario is the following:

	 One web server runninng kernel 2.4.9-e-12(smp), it is used to host an 
Apache webserver with an integrated application server. The system has 2Gb 
of RAM and 2Gb of swap. The last day an strange thing happened. We tried to 
connect to our system using ssh and we can´t, after many attempts we could 
connect to the system and saw that we couldn´t connect because there was a 
lack of memory. Every proccess you tried to start failed  and gave the 
following error message" fork failed: Can´t allocate memory (errno=12)".

The output of the free -k command showed that the swap space(there was only 
5 Mb of free RAM) wasn´t being used and we don´t understand why. We have 
found a lot of similar cases of systems that couldn´t fork but were plenty 
of unused swap space so we thought we would find answers for this problem 
but we haven´t found any(although we have looked for one a lot).

    We think that perhaps our freepages settings are too low( 1.6-4.5-7.4 
Mb) and if we merge this low values with an excesive fragmented memory this 
could explain our memory squeeze problems. Some of us have proposed the 
theory that everytime a proccess is started it needs a little quantity of 
contiguous memory and that if the system can´t provide it to the process it 
dies before the fork is completed. Any idea about what can be happening 
here?

Regards,
Mario.

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Re: Is kswapd working right?

[Jose Luis Domingo Lopez]

On Tuesday, 30 September 2003, at 10:55:10 +0000,
mario camuñas wrote:

> 	 One web server runninng kernel 2.4.9-e-12(smp), it is used to host 
>
That kernel version is ages old and, if it where a vanilla 2.4.9, maybe
one on the hardest to keep on working as expected in the 2.4.x series.

>From the version number one can believe your kernel comes precompiled by
your vendor, and maybe you should contact it before anything else.
Upgrading the kernel to the latest available version provided by your
vendor, if at all possible, could also help a lot.

-- 
Jose Luis Domingo Lopez
Linux Registered User #189436     Debian Linux Sid (Linux 2.6.0-test5-mm3)

Re: Is kswapd working right?

[Gianni Tedesco]

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On Tue, 2003-09-30 at 12:55, mario camuñas wrote:
> The output of the free -k command showed that the swap space(there was only 
> 5 Mb of free RAM) wasn´t being used and we don´t understand why. We have 

is the swap space actually enabled? ie. does it show in /proc/swaps ?

-- 
// Gianni Tedesco (gianni at scaramanga dot co dot uk)
lynx --source www.scaramanga.co.uk/gianni-at-ecsc.asc | gpg --import
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