Re: Re: Kernel doesn't free Cached Memory

Re: Re: Kernel doesn't free Cached Memory

[Vinicius]

[-- Attachment #1: Mail message body --]
[-- Type: text/plain, Size: 1814 bytes --]

On Fri, 2005-07-22 at 08:27 -0300, Vinicius wrote: 
[...] 
>>    I have a server with 2 Pentium 4 HT processors and 32 GB of >>RAM, 
this 
>> server runs lots of applications that consume lots of memory to. >>When I 
>>stop 
>> this applications, the kernel doesn't free memory (the  memory >>still in 
>>use) 
>> and the server cache lots of memory (~27GB). When I start this 
>>applications, 
>> the kernel sends  "Out of Memory" messages and kill some random 
>> applications. 
>> 
>>    Anyone know how can I reduce the kernel cached memory on RHEL >>3 
(kernel 
>> 2.4.21-32.ELsmp - Trial version)? There is a way to reduce the >>kernel 
>>cached 
>> memory utilization? 

>Probably RedHat's support can answer this for RHEL 3. 
> 
>	Bernd 
>-- 
> Firmix Software GmbH                   http://www.firmix.at/ 
>mobil: +43 664 4416156                 fax: +43 1 7890849-55 
>          Embedded Linux Development and Services 

Bernd, 

   The server runs RHEL Trial Version, without support... for tests purpose. 

   When I compile and run the following tester program: 

#include <stdio.h> 
#include <string.h> 
#include <stdlib.h> 

int main (void) { 
        int n = 0; 
        char *p; 

        while (1) { 
                if ((p = malloc(1<<20)) == NULL) { 
                        printf("malloc failure after %d MiB\n", n); 
                        return 0; 
                } 
                memset (p, 0, (1<<20)); 
                printf ("got %d MiB\n", ++n); 
        } 
} 

   The server alocates lots of free memory (including swap) to the tester 
program and when its finish, lots of cached memory are freed. 

   Have someone an idea why it's happens? Or how can I force the kernel to 
frees cached memory? 

Thanks again (sorry my bad eglish again!) 

Vinicius. 
Protolink Consultoria. 

Re: Re: Kernel doesn't free Cached Memory

[Adrian Bunk]

On Fri, Jul 22, 2005 at 09:02:05AM -0300, Vinicius wrote:
Content-Description: Mail message body
> On Fri, 2005-07-22 at 08:27 -0300, Vinicius wrote: 
> [...] 
> >>    I have a server with 2 Pentium 4 HT processors and 32 GB of >>RAM, 
> this 
> >> server runs lots of applications that consume lots of memory to. >>When I 
> >>stop 
> >> this applications, the kernel doesn't free memory (the  memory >>still in 
> >>use) 
> >> and the server cache lots of memory (~27GB). When I start this 
> >>applications, 
> >> the kernel sends  "Out of Memory" messages and kill some random 
> >> applications. 
> >> 
> >>    Anyone know how can I reduce the kernel cached memory on RHEL >>3 
> (kernel 
> >> 2.4.21-32.ELsmp - Trial version)? There is a way to reduce the >>kernel 
> >>cached 
> >> memory utilization? 
> 
> >Probably RedHat's support can answer this for RHEL 3. 
> > 
> >	Bernd 
> 
> Bernd, 
> 
>    The server runs RHEL Trial Version, without support... for tests purpose. 
>...

The answers you already got are:
- for that much memory, 64bit processors are really recommended
- 2.6 kernels are a better choice for this scenario
- linux-kernel doesn't support vendor kernels, does the same problem 
  occur with kernel 2.6.12 ?

Another thing that surprises me is that why you are testing an old 
version of RHEL.

If you want to build a new system, you should better test RHEL 4.

> Vinicius. 
> Protolink Consultoria. 

cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed