On Fri, Sep 14, 2018 at 07:58:01PM +0530, Pintu Kumar wrote:
> Hi All,
>
> Board: Hikey620 ARM64
> Kernel: 4.9.20
>
> I am trying to verify KSM (Kernel Same Page Merging) functionality on
> 4.9 Kernel using "mmap" and madvise user space test utility.
> But to my observation, it seems KSM is not working for me.
> CONFIG_KSM=y is enabled in kernel.
> ksm_init is also called during boot up.
> 443 ? SN 0:00 [ksmd]
>
> ksmd thread is also running.
>
> However, when I see the sysfs, no values are written.
> ~ # grep -H '' /sys/kernel/mm/ksm/*
> /sys/kernel/mm/ksm/pages_hashed:0
> /sys/kernel/mm/ksm/pages_scanned:0
> /sys/kernel/mm/ksm/pages_shared:0
> /sys/kernel/mm/ksm/pages_sharing:0
> /sys/kernel/mm/ksm/pages_to_scan:200
> /sys/kernel/mm/ksm/pages_unshared:0
> /sys/kernel/mm/ksm/pages_volatile:0
> /sys/kernel/mm/ksm/run:1
> /sys/kernel/mm/ksm/sleep_millisecs:1000
>
> So, please let me know if I am doing any thing wrong.
>
> This is the test utility:
> int main(int argc, char *argv[])
> {
> int i, n, size;
> char *buffer;
> void *addr;
>
> n = 100;
> size = 100 * getpagesize();
> for (i = 0; i < n; i++) {
> buffer = (char *)malloc(size);
> memset(buffer, 0xff, size);
> addr = mmap(NULL, size,
> PROT_READ | PROT_EXEC | PROT_WRITE,
> MAP_PRIVATE | MAP_ANONYMOUS,
> -1, 0);
> madvise(addr, size, MADV_MERGEABLE);
Just mmap'ing an area does not allocate any physical pages, so KSM has
nothing to merge.
You need to memset(addr,...) after mmap().
> sleep(1);
> }
> printf("Done....press ^C\n");
>
> pause();
>
> return 0;
> }
>
>
>
> Thanks,
> Pintu
>
--
Sincerely yours,
Mike.
