Memory Usage Growth in File access

Memory Usage Growth in File access

[s.deepak]

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Hi All,

I am  facing an issue in file operation, when we read/write continuously to  a large file in our  ppc 405 based device , memory usage shown in /proc/meminfo   increases by the number of bytes accessed.And after closing the application also the memory used is not released and  it goes to cached memory .
We are using 2.4.20 kernel in our device.We are not sure whether the /proc/meminfo shows the erroneous output or the file read/write routines got any problem.
Can anyone suggest me some idea how to trace out the problem.

I have given the sample code  below.
The memory consumption grows and it takes about 10 MB memory space [10000 * 1024] when i run the below given code.
When i look into /proc/meminfo the free memory is reduced by 10 MB and Cache Memory & Used memory is increased by 10 mb after running this application.
When i run the below given code first time the memory grows,when  i run succesively it doesn't grow again , may be using the already taken memory.



int main()
{

FILE *fp;

unsigned long int i;
unsigned char data[1024];

fp=fopen("test.txt","r");
for(i=0;i<10000;i++)
{

      fread(data,1024,1,fp);
}
fclose(fp);
}


With Thanks & Regards,
Deepak S

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Re: Memory Usage Growth in File access

[Wolfgang Denk]

In message <02cb01c54ee3$87e93ec0$4000a8c0@DeepakS> you wrote:
>
> I am  facing an issue in file operation, when we read/write continuously
> to  a large file in our  ppc 405 based device , memory usage shown in
> /proc/meminfo   increases by the number of bytes accessed.And after
> closing the application also the memory used is not released and  it
> goes to cached memory .

Welcome to the world of efficient use of resources.

What you see is perfectly normal behaviour and  one  of  the  reasons
that LInux provides excellent performance.

> Can anyone suggest me some idea how to trace out the problem.

There is no problem. What you see is normal the way it  was  designed
to work.

> When i run the below given code first time the memory grows,when  i run
> succesively it doesn't grow again , may be using the already taken
> memory.

Indeed. Also if you have a way to  trace  accesses  to  your  storage
media  you  will see that the secondrun needs much less accesses, and
is faster, too.

Welcome to Unix.

Best regards,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de
Today is the yesterday you worried about tomorrow.