be clear about which cache? Are you interested in dentry cache, inode cache or page cache? dentry cache and inode cache can grow only by access to filesystem, access multiple files on your system. For page cache increase, you can simple copy a very large file say 1G.
> I write a test program as below but from top, the size of cache seems
no change
I didnt get the purpose of your test program, perhaps you want to put memory pressure on your system. What your test program is doing is just calling malloc, it does nothing but grow the virtual memory area of your heap, It wont allocate physical pages until you access the virtual address, try to write some bytes on each allocated memory such that each 4K page is accessed. This results in page vault in kernel and since your address is valid so it will allocate a page for you. Typically called Demand Paging.
If you really want to put memory pressure, try allocating memory in kernel through kmalloc.
Rajat
On Mon, Nov 1, 2010 at 8:56 AM, loody <miloody@xxxxxxxxx> wrote:
Dear all:
I have some questions about virtual memory (VM) subsystem of the Linux
kernel.
1. From linux doc, there is drop_caches in /proc/ which can let us to
free the cache that kernel used, such as dentries and inodes, etc.
I know i can echo 1, 2 or 3 to free different level of caches in the
linux kernel, but is there any more elegant or programming rule that I
can follow to let it used more efficiently?
2. what kind of system call will increase the size of cache?
I write a test program as below but from top, the size of cache seems
no change
#include<stdio.h>
#include<stdlib.h>
int main(void)
{
int index;
char input;
char * point[1024];
for(index=0;index<1024;index++)
{
point[index]=malloc(1024*1024);
printf("please input any charter for going down:\n");
scanf("%c",&input);
}
}
the memory usage of test.mips increased but the cached size is always
4916k as below:
Mem: 8352K used, 132800K free, 0K shrd, 60K buff, 4916K cached
Load average: 0.00 0.00 0.00
PID USER STATUS VSZ PPID %CPU %MEM COMMAND
400 0 SW 668 1 0.3 0.4 busybox.telnetd
498 0 RW 584 408 0.3 0.4 top
500 0 SW 10156 317 0.0 7.1 test.mips
317 0 SW 596 1 0.0 0.4 sh
408 0 SW 592 400 0.0 0.4 sh
1 0 SW 584 0 0.0 0.4 init
5 0 SW< 0 2 0.0 0.0 khelper
86 0 SW< 0 2 0.0 0.0 khubd
3 0 SW< 0 2 0.0 0.0 ksoftirqd/0
76 0 SW< 0 2 0.0 0.0 kblockd/0
4 0 SW< 0 2 0.0 0.0 events/0
2 0 SW< 0 0 0.0 0.0 kthreadd
112 0 SW 0 2 0.0 0.0 pdflush
113 0 SW< 0 2 0.0 0.0 kswapd0
8 0 SW< 0 2 0.0 0.0 async/mgr
116 0 SW< 0 2 0.0 0.0 crypto/0
252 0 SW< 0 2 0.0 0.0 mtdblockd
254 0 SW< 0 2 0.0 0.0 nftld
255 0 SW< 0 2 0.0 0.0 inftld
286 0 SW< 0 2 0.0 0.0 rpciod/0
253 0 SW< 0 2 0.0 0.0 ftld
89 0 SW< 0 2 0.0 0.0 kseriod
111 0 SW 0 2 0.0 0.0 pdflush
448 0 SW< 0 2 0.0 0.0 scsi_eh_1
449 0 SW< 0 2 0.0 0.0 usb-storage
114 0 SW< 0 2 0.0 0.0 nfsiod
115 0 SW< 0 2 0.0 0.0 cifsoplockd
Mem: 8352K used, 132800K free, 0K shrd, 60K buff, 4916K cached
Load average: 0.04 0.01 0.00
PID USER STATUS VSZ PPID %CPU %MEM COMMAND
501 0 RW 584 408 0.5 0.4 top
400 0 SW 668 1 0.3 0.4 busybox.telnetd
500 0 SW 37912 317 0.0 26.8 test.mips
317 0 SW 596 1 0.0 0.4 sh
408 0 SW 592 400 0.0 0.4 sh
1 0 SW 584 0 0.0 0.4 init
5 0 SW< 0 2 0.0 0.0 khelper
86 0 SW< 0 2 0.0 0.0 khubd
3 0 SW< 0 2 0.0 0.0 ksoftirqd/0
76 0 SW< 0 2 0.0 0.0 kblockd/0
4 0 SW< 0 2 0.0 0.0 events/0
2 0 SW< 0 0 0.0 0.0 kthreadd
112 0 SW 0 2 0.0 0.0 pdflush
113 0 SW< 0 2 0.0 0.0 kswapd0
8 0 SW< 0 2 0.0 0.0 async/mgr
116 0 SW< 0 2 0.0 0.0 crypto/0
252 0 SW< 0 2 0.0 0.0 mtdblockd
254 0 SW< 0 2 0.0 0.0 nftld
255 0 SW< 0 2 0.0 0.0 inftld
286 0 SW< 0 2 0.0 0.0 rpciod/0
253 0 SW< 0 2 0.0 0.0 ftld
89 0 SW< 0 2 0.0 0.0 kseriod
111 0 SW 0 2 0.0 0.0 pdflush
448 0 SW< 0 2 0.0 0.0 scsi_eh_1
449 0 SW< 0 2 0.0 0.0 usb-storage
114 0 SW< 0 2 0.0 0.0 nfsiod
115 0 SW< 0 2 0.0 0.0 cifsoplockd
appreciate your kind help,
miloody
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