KSM not working in 4.9 Kernel

KSM not working in 4.9 Kernel

[Pintu Kumar]

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);
                sleep(1);
        }
        printf("Done....press ^C\n");

        pause();

        return 0;
}



Thanks,
Pintu

Re: KSM not working in 4.9 Kernel

[Yang Shi]

Hi Pintu,

I recall there are some ksm test cases in LTP. Did you try them out?
On Fri, Sep 14, 2018 at 7:28 AM Pintu Kumar <pintu.ping@gmail.com> 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);
>                 sleep(1);
>         }
>         printf("Done....press ^C\n");
>
>         pause();
>
>         return 0;
> }
>
>
>
> Thanks,
> Pintu
>

Re: KSM not working in 4.9 Kernel

[Pintu Kumar]

On Fri, 14 Sep 2018, 10:42 pm Yang Shi, <shy828301@gmail.com> wrote:
>
> Hi Pintu,
>
> I recall there are some ksm test cases in LTP. Did you try them out?

No. I haven't seen the LTP test. I will check out now.
But I wonder what is the problem with my test?


> On Fri, Sep 14, 2018 at 7:28 AM Pintu Kumar <pintu.ping@gmail.com> 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);
> >                 sleep(1);
> >         }
> >         printf("Done....press ^C\n");
> >
> >         pause();
> >
> >         return 0;
> > }
> >
> >
> >
> > Thanks,
> > Pintu
> >

Re: KSM not working in 4.9 Kernel

[Mike Rapoport]

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.

Re: KSM not working in 4.9 Kernel

[Pintu Kumar]

On Sun, Sep 16, 2018 at 9:02 PM Mike Rapoport <rppt@linux.vnet.ibm.com> wrote:
>
> 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().
>

Yes, I am doing memset also.
memset(addr, 0xff, size);

But still no effect.
And I checked LTP test cases. It almost doing the same thing.

I observed that [ksmd] thread is not waking up at all.
I gave some print inside it, but I could never saw that prints coming.
I could not find it running either in top command during the operation.
Is there anything needs to be done, to wakw up ksmd?
I already set: echo 1 > /sys/kernel/mm/ksm.



> >                 sleep(1);
> >         }
> >         printf("Done....press ^C\n");
> >
> >         pause();
> >
> >         return 0;
> > }
> >
> >
> >
> > Thanks,
> > Pintu
> >
>
> --
> Sincerely yours,
> Mike.
>

Re: KSM not working in 4.9 Kernel

[Mike Rapoport]

On Sun, Sep 16, 2018 at 10:35:17PM +0530, Pintu Kumar wrote:
> On Sun, Sep 16, 2018 at 9:02 PM Mike Rapoport <rppt@linux.vnet.ibm.com> wrote:
> >
> > 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().
> >
> 
> Yes, I am doing memset also.
> memset(addr, 0xff, size);
> 
> But still no effect.
> And I checked LTP test cases. It almost doing the same thing.
> 
> I observed that [ksmd] thread is not waking up at all.
> I gave some print inside it, but I could never saw that prints coming.
> I could not find it running either in top command during the operation.
> Is there anything needs to be done, to wakw up ksmd?
> I already set: echo 1 > /sys/kernel/mm/ksm.

It should be echo 1 > /sys/kernel/mm/ksm/run
 
> 
> 
> > >                 sleep(1);
> > >         }
> > >         printf("Done....press ^C\n");
> > >
> > >         pause();
> > >
> > >         return 0;
> > > }
> > >
> > >
> > >
> > > Thanks,
> > > Pintu
> > >
> >
> > --
> > Sincerely yours,
> > Mike.
> >
> 

-- 
Sincerely yours,
Mike.

Re: KSM not working in 4.9 Kernel

[Pintu Kumar]

On Mon, Sep 17, 2018 at 10:07 AM Mike Rapoport <rppt@linux.vnet.ibm.com> wrote:
>
> On Sun, Sep 16, 2018 at 10:35:17PM +0530, Pintu Kumar wrote:
> > On Sun, Sep 16, 2018 at 9:02 PM Mike Rapoport <rppt@linux.vnet.ibm.com> wrote:
> > >
> > > 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().
> > >
> >
> > Yes, I am doing memset also.
> > memset(addr, 0xff, size);
> >
> > But still no effect.
> > And I checked LTP test cases. It almost doing the same thing.
> >
> > I observed that [ksmd] thread is not waking up at all.
> > I gave some print inside it, but I could never saw that prints coming.
> > I could not find it running either in top command during the operation.
> > Is there anything needs to be done, to wakw up ksmd?
> > I already set: echo 1 > /sys/kernel/mm/ksm.
>
> It should be echo 1 > /sys/kernel/mm/ksm/run
>

Oh yes, sorry for the typo.
I tried the same, but still ksm is not getting invoked.
Could someone confirm if KSM was working in 4.9 kernel?


> >
> >
> > > >                 sleep(1);
> > > >         }
> > > >         printf("Done....press ^C\n");
> > > >
> > > >         pause();
> > > >
> > > >         return 0;
> > > > }
> > > >
> > > >
> > > >
> > > > Thanks,
> > > > Pintu
> > > >
> > >
> > > --
> > > Sincerely yours,
> > > Mike.
> > >
> >
>
> --
> Sincerely yours,
> Mike.
>

Re: KSM not working in 4.9 Kernel

[Pintu Kumar]

On Mon, Sep 17, 2018 at 11:46 AM Pintu Kumar <pintu.ping@gmail.com> wrote:
> > > But still no effect.
> > > And I checked LTP test cases. It almost doing the same thing.
> > >
> > > I observed that [ksmd] thread is not waking up at all.
> > > I gave some print inside it, but I could never saw that prints coming.
> > > I could not find it running either in top command during the operation.
> > > Is there anything needs to be done, to wakw up ksmd?
> > > I already set: echo 1 > /sys/kernel/mm/ksm.
> >
> > It should be echo 1 > /sys/kernel/mm/ksm/run
> >
>
> Oh yes, sorry for the typo.
> I tried the same, but still ksm is not getting invoked.
> Could someone confirm if KSM was working in 4.9 kernel?
>

Ok, it's working now. I have to explicitly stop the ksm thread to see
the statistics.
Also there was some internal patch that was setting vm_flags to
VM_MERGABLE thus causing ksm_advise call to return.

# echo 1 > /sys/kernel/mm/ksm/run
# ./malloc-test.out &
# echo 0 > /sys/kernel/mm/ksm/run

~ # grep -H '' /sys/kernel/mm/ksm/*
/sys/kernel/mm/ksm/full_scans:105
/sys/kernel/mm/ksm/pages_shared:1
/sys/kernel/mm/ksm/pages_sharing:999
/sys/kernel/mm/ksm/pages_to_scan:100
/sys/kernel/mm/ksm/pages_unshared:0
/sys/kernel/mm/ksm/pages_volatile:0
/sys/kernel/mm/ksm/run:0
/sys/kernel/mm/ksm/sleep_millisecs:20


However, I have one doubt.
Is the above data correct, for the below program?

int main(int argc, char *argv[])
{
        int i, n, size, ret;
        char *buffer;
        void *addr;

        n = 10;
        size = 100 * getpagesize();
        for (i = 0; i < n; i++) {
                buffer = (char *)malloc(size);
                memset(buffer, 0xff, size);
                madvise(buffer, size, MADV_MERGEABLE);
                addr =  mmap(NULL, size,
                           PROT_READ | PROT_EXEC | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS,
                           -1, 0);
                memset(addr, 0xff, size);
                ret = madvise(addr, size, MADV_MERGEABLE);
                if (ret < 0) {
                        fprintf(stderr, "madvise failed: ret: %d,
reason: %s\n", ret, strerror(errno));
                }
                usleep(500);
        }
        printf("Done....press ^C\n");

        pause();

        return 0;
}


Thanks,
Pintu

Re: KSM not working in 4.9 Kernel

[Mike Rapoport]

On Mon, Sep 17, 2018 at 05:25:27PM +0530, Pintu Kumar wrote:
> On Mon, Sep 17, 2018 at 11:46 AM Pintu Kumar <pintu.ping@gmail.com> wrote:
> > > > But still no effect.
> > > > And I checked LTP test cases. It almost doing the same thing.
> > > >
> > > > I observed that [ksmd] thread is not waking up at all.
> > > > I gave some print inside it, but I could never saw that prints coming.
> > > > I could not find it running either in top command during the operation.
> > > > Is there anything needs to be done, to wakw up ksmd?
> > > > I already set: echo 1 > /sys/kernel/mm/ksm.
> > >
> > > It should be echo 1 > /sys/kernel/mm/ksm/run
> > >
> >
> > Oh yes, sorry for the typo.
> > I tried the same, but still ksm is not getting invoked.
> > Could someone confirm if KSM was working in 4.9 kernel?
> >
> 
> Ok, it's working now. I have to explicitly stop the ksm thread to see
> the statistics.
> Also there was some internal patch that was setting vm_flags to
> VM_MERGABLE thus causing ksm_advise call to return.
> 
> # echo 1 > /sys/kernel/mm/ksm/run
> # ./malloc-test.out &
> # echo 0 > /sys/kernel/mm/ksm/run
> 
> ~ # grep -H '' /sys/kernel/mm/ksm/*
> /sys/kernel/mm/ksm/full_scans:105
> /sys/kernel/mm/ksm/pages_shared:1
> /sys/kernel/mm/ksm/pages_sharing:999
> /sys/kernel/mm/ksm/pages_to_scan:100
> /sys/kernel/mm/ksm/pages_unshared:0
> /sys/kernel/mm/ksm/pages_volatile:0
> /sys/kernel/mm/ksm/run:0
> /sys/kernel/mm/ksm/sleep_millisecs:20
> 
> 
> However, I have one doubt.
> Is the above data correct, for the below program?

You have 1 shared page and 999 additional references to that page
 
> int main(int argc, char *argv[])
> {
>         int i, n, size, ret;
>         char *buffer;
>         void *addr;
> 
>         n = 10;
>         size = 100 * getpagesize();
>         for (i = 0; i < n; i++) {
>                 buffer = (char *)malloc(size);
>                 memset(buffer, 0xff, size);
>                 madvise(buffer, size, MADV_MERGEABLE);o

This madvise() call should fail because buffer won't be page aligned

>                 addr =  mmap(NULL, size,
>                            PROT_READ | PROT_EXEC | PROT_WRITE,
> MAP_PRIVATE | MAP_ANONYMOUS,
>                            -1, 0);
>                 memset(addr, 0xff, size);
>                 ret = madvise(addr, size, MADV_MERGEABLE);
>                 if (ret < 0) {
>                         fprintf(stderr, "madvise failed: ret: %d,
> reason: %s\n", ret, strerror(errno));
>                 }
>                 usleep(500);
>         }
>         printf("Done....press ^C\n");
> 
>         pause();
> 
>         return 0;
> }
> 
> 
> Thanks,
> Pintu
> 

-- 
Sincerely yours,
Mike.

Re: KSM not working in 4.9 Kernel

[Pintu Kumar]

Hi,

Thank you so much for all your reply so far.
I have few more doubts to understand the output from ksm sysfs.
Device: Hikey620 - ARM64 - Linux 4.9.20
With HUGE page enabled:
CONFIG_TRANSPARENT_HUGEPAGE=y
CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS=y
# CONFIG_TRANSPARENT_HUGEPAGE_MADVISE is not set

Currently, I get this output, when I run below program with ksm:

~ # grep -H '' /sys/kernel/mm/ksm/*
/sys/kernel/mm/ksm/full_scans:29
/sys/kernel/mm/ksm/page_comparisons:39584
/sys/kernel/mm/ksm/pages_hashed:11672
/sys/kernel/mm/ksm/pages_scanned:21766
/sys/kernel/mm/ksm/pages_shared:3
/sys/kernel/mm/ksm/pages_sharing:10097
/sys/kernel/mm/ksm/pages_to_scan:200
/sys/kernel/mm/ksm/pages_unshared:53
/sys/kernel/mm/ksm/pages_volatile:1
/sys/kernel/mm/ksm/run:0
/sys/kernel/mm/ksm/sleep_millisecs:1000
---------------------------

int main(int argc, char *argv[])
{
        int i, n, size, ret;
        char *buffer;
        void *addr;

        n = 100;
        size = 100 * getpagesize();
        for (i = 0; i < n; i++) {
                buffer = (char *)malloc(size);
                memset(buffer, 0xff, size);
                madvise(buffer, size, MADV_MERGEABLE);
                if (ret < 0) {
                        fprintf(stderr, "malloc madvise failed: ret:
%d, reason: %s\n", ret, strerror(errno));
                }
                usleep(500);
        }
        printf("Done....press ^C\n");
        pause();
        return 0;
}
Note: madvise() system call is not failing here, as mentioned earlier.
I guess the page is aligned with getpagesize().
Then I do this to invoke ksm:
# echo 1 > /sys/kernel/mm/ksm/run
# ./malloc-test.out &
# sleep 5
# echo 0 > /sys/kernel/mm/ksm/run
#

Also, the anon pages in the system shows like this:
BEFORE:
-------------
~ # cat /proc/meminfo | grep -i anon
Active(anon):      40740 kB
Inactive(anon):        0 kB
AnonPages:         40760 kB
AnonHugePages:         0 kB

AFTER MERGING:
--------------------------
~ # cat /proc/meminfo | grep -i anon
Active(anon):        440 kB
Inactive(anon):        0 kB
AnonPages:           188 kB
AnonHugePages:         0 kB

I want to understand the KSM output w.r.t to the above program, and
cross-check if the output is correct.
Can someone help me to understand it?

As of now, what I understood is that:
- I am allocating around 400KB of memory 100 times. That is: 100 * 100
* 4K = 10000 pages (which are all with similar content).
- Output says: 10097 page_sharing happened.
- Pages currently shared is: 3
- So total pages are: 10097 + 3 = 10100

I could not understand from where the additional 100 pages came from?
Also, why some pages are shown as: pages_unshared ?
What can I interpret from this?
And, what does it mean by: pages_volatile:1 ?

Basically, I wanted to understand, is there any problem with the above
output, or it is fine.
If it is fine, how to prove it?



Thanks,
Pintu

On Mon, Sep 17, 2018 at 8:29 PM Mike Rapoport <rppt@linux.vnet.ibm.com> wrote:
>
> On Mon, Sep 17, 2018 at 05:25:27PM +0530, Pintu Kumar wrote:
> > On Mon, Sep 17, 2018 at 11:46 AM Pintu Kumar <pintu.ping@gmail.com> wrote:
> > > > > But still no effect.
> > > > > And I checked LTP test cases. It almost doing the same thing.
> > > > >
> > > > > I observed that [ksmd] thread is not waking up at all.
> > > > > I gave some print inside it, but I could never saw that prints coming.
> > > > > I could not find it running either in top command during the operation.
> > > > > Is there anything needs to be done, to wakw up ksmd?
> > > > > I already set: echo 1 > /sys/kernel/mm/ksm.
> > > >
> > > > It should be echo 1 > /sys/kernel/mm/ksm/run
> > > >
> > >
> > > Oh yes, sorry for the typo.
> > > I tried the same, but still ksm is not getting invoked.
> > > Could someone confirm if KSM was working in 4.9 kernel?
> > >
> >
> > Ok, it's working now. I have to explicitly stop the ksm thread to see
> > the statistics.
> > Also there was some internal patch that was setting vm_flags to
> > VM_MERGABLE thus causing ksm_advise call to return.
> >
> > # echo 1 > /sys/kernel/mm/ksm/run
> > # ./malloc-test.out &
> > # echo 0 > /sys/kernel/mm/ksm/run
> >
> > ~ # grep -H '' /sys/kernel/mm/ksm/*
> > /sys/kernel/mm/ksm/full_scans:105
> > /sys/kernel/mm/ksm/pages_shared:1
> > /sys/kernel/mm/ksm/pages_sharing:999
> > /sys/kernel/mm/ksm/pages_to_scan:100
> > /sys/kernel/mm/ksm/pages_unshared:0
> > /sys/kernel/mm/ksm/pages_volatile:0
> > /sys/kernel/mm/ksm/run:0
> > /sys/kernel/mm/ksm/sleep_millisecs:20
> >
> >
> > However, I have one doubt.
> > Is the above data correct, for the below program?
>
> You have 1 shared page and 999 additional references to that page
>
> > int main(int argc, char *argv[])
> > {
> >         int i, n, size, ret;
> >         char *buffer;
> >         void *addr;
> >
> >         n = 10;
> >         size = 100 * getpagesize();
> >         for (i = 0; i < n; i++) {
> >                 buffer = (char *)malloc(size);
> >                 memset(buffer, 0xff, size);
> >                 madvise(buffer, size, MADV_MERGEABLE);o
>
> This madvise() call should fail because buffer won't be page aligned
>
> >                 addr =  mmap(NULL, size,
> >                            PROT_READ | PROT_EXEC | PROT_WRITE,
> > MAP_PRIVATE | MAP_ANONYMOUS,
> >                            -1, 0);
> >                 memset(addr, 0xff, size);
> >                 ret = madvise(addr, size, MADV_MERGEABLE);
> >                 if (ret < 0) {
> >                         fprintf(stderr, "madvise failed: ret: %d,
> > reason: %s\n", ret, strerror(errno));
> >                 }
> >                 usleep(500);
> >         }
> >         printf("Done....press ^C\n");
> >
> >         pause();
> >
> >         return 0;
> > }
> >
> >
> > Thanks,
> > Pintu
> >
>
> --
> Sincerely yours,
> Mike.
>

Re: KSM not working in 4.9 Kernel

[Mike Rapoport]

On Thu, Sep 20, 2018 at 05:21:20PM +0530, Pintu Kumar wrote:
> Hi,
> 
> Thank you so much for all your reply so far.
> I have few more doubts to understand the output from ksm sysfs.
> Device: Hikey620 - ARM64 - Linux 4.9.20
> With HUGE page enabled:
> CONFIG_TRANSPARENT_HUGEPAGE=y
> CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS=y
> # CONFIG_TRANSPARENT_HUGEPAGE_MADVISE is not set
> 
> Currently, I get this output, when I run below program with ksm:
> 
> ~ # grep -H '' /sys/kernel/mm/ksm/*
> /sys/kernel/mm/ksm/full_scans:29
> /sys/kernel/mm/ksm/page_comparisons:39584
> /sys/kernel/mm/ksm/pages_hashed:11672
> /sys/kernel/mm/ksm/pages_scanned:21766
> /sys/kernel/mm/ksm/pages_shared:3
> /sys/kernel/mm/ksm/pages_sharing:10097
> /sys/kernel/mm/ksm/pages_to_scan:200
> /sys/kernel/mm/ksm/pages_unshared:53
> /sys/kernel/mm/ksm/pages_volatile:1
> /sys/kernel/mm/ksm/run:0
> /sys/kernel/mm/ksm/sleep_millisecs:1000
> ---------------------------
> 
> int main(int argc, char *argv[])
> {
>         int i, n, size, ret;
>         char *buffer;
>         void *addr;
> 
>         n = 100;
>         size = 100 * getpagesize();
>         for (i = 0; i < n; i++) {
>                 buffer = (char *)malloc(size);
>                 memset(buffer, 0xff, size);
>                 madvise(buffer, size, MADV_MERGEABLE);
>                 if (ret < 0) {
>                         fprintf(stderr, "malloc madvise failed: ret:
> %d, reason: %s\n", ret, strerror(errno));
>                 }
>                 usleep(500);
>         }
>         printf("Done....press ^C\n");
>         pause();
>         return 0;
> }
> Note: madvise() system call is not failing here, as mentioned earlier.
> I guess the page is aligned with getpagesize().
> Then I do this to invoke ksm:
> # echo 1 > /sys/kernel/mm/ksm/run
> # ./malloc-test.out &
> # sleep 5
> # echo 0 > /sys/kernel/mm/ksm/run
> #
> 
> Also, the anon pages in the system shows like this:
> BEFORE:
> -------------
> ~ # cat /proc/meminfo | grep -i anon
> Active(anon):      40740 kB
> Inactive(anon):        0 kB
> AnonPages:         40760 kB
> AnonHugePages:         0 kB
> 
> AFTER MERGING:
> --------------------------
> ~ # cat /proc/meminfo | grep -i anon
> Active(anon):        440 kB
> Inactive(anon):        0 kB
> AnonPages:           188 kB
> AnonHugePages:         0 kB
> 
> I want to understand the KSM output w.r.t to the above program, and
> cross-check if the output is correct.
> Can someone help me to understand it?
> 
> As of now, what I understood is that:
> - I am allocating around 400KB of memory 100 times. That is: 100 * 100
> * 4K = 10000 pages (which are all with similar content).
> - Output says: 10097 page_sharing happened.
> - Pages currently shared is: 3
> - So total pages are: 10097 + 3 = 10100
> 
> I could not understand from where the additional 100 pages came from?
> Also, why some pages are shown as: pages_unshared ?
> What can I interpret from this?
> And, what does it mean by: pages_volatile:1 ?
> 
> Basically, I wanted to understand, is there any problem with the above
> output, or it is fine.
> If it is fine, how to prove it?

The ksm sysfs attributes are described at
Documentation/admin-guide/mm/ksm.rst or online at [1].

The numbers look sane in general. The additional pages may come from malloc
metadata that is created by libc when you allocate memory.

I'd recommend to use mmap() or posix_memalign() with page size alignment to
get exact amount of page aligned memory.

[1] https://www.kernel.org/doc/html/latest/admin-guide/mm/ksm.html
 
 
 
> Thanks,
> Pintu
> 
> On Mon, Sep 17, 2018 at 8:29 PM Mike Rapoport <rppt@linux.vnet.ibm.com> wrote:
> >
> > On Mon, Sep 17, 2018 at 05:25:27PM +0530, Pintu Kumar wrote:
> > > On Mon, Sep 17, 2018 at 11:46 AM Pintu Kumar <pintu.ping@gmail.com> wrote:
> > > > > > But still no effect.
> > > > > > And I checked LTP test cases. It almost doing the same thing.
> > > > > >
> > > > > > I observed that [ksmd] thread is not waking up at all.
> > > > > > I gave some print inside it, but I could never saw that prints coming.
> > > > > > I could not find it running either in top command during the operation.
> > > > > > Is there anything needs to be done, to wakw up ksmd?
> > > > > > I already set: echo 1 > /sys/kernel/mm/ksm.
> > > > >
> > > > > It should be echo 1 > /sys/kernel/mm/ksm/run
> > > > >
> > > >
> > > > Oh yes, sorry for the typo.
> > > > I tried the same, but still ksm is not getting invoked.
> > > > Could someone confirm if KSM was working in 4.9 kernel?
> > > >
> > >
> > > Ok, it's working now. I have to explicitly stop the ksm thread to see
> > > the statistics.
> > > Also there was some internal patch that was setting vm_flags to
> > > VM_MERGABLE thus causing ksm_advise call to return.
> > >
> > > # echo 1 > /sys/kernel/mm/ksm/run
> > > # ./malloc-test.out &
> > > # echo 0 > /sys/kernel/mm/ksm/run
> > >
> > > ~ # grep -H '' /sys/kernel/mm/ksm/*
> > > /sys/kernel/mm/ksm/full_scans:105
> > > /sys/kernel/mm/ksm/pages_shared:1
> > > /sys/kernel/mm/ksm/pages_sharing:999
> > > /sys/kernel/mm/ksm/pages_to_scan:100
> > > /sys/kernel/mm/ksm/pages_unshared:0
> > > /sys/kernel/mm/ksm/pages_volatile:0
> > > /sys/kernel/mm/ksm/run:0
> > > /sys/kernel/mm/ksm/sleep_millisecs:20
> > >
> > >
> > > However, I have one doubt.
> > > Is the above data correct, for the below program?
> >
> > You have 1 shared page and 999 additional references to that page
> >
> > > int main(int argc, char *argv[])
> > > {
> > >         int i, n, size, ret;
> > >         char *buffer;
> > >         void *addr;
> > >
> > >         n = 10;
> > >         size = 100 * getpagesize();
> > >         for (i = 0; i < n; i++) {
> > >                 buffer = (char *)malloc(size);
> > >                 memset(buffer, 0xff, size);
> > >                 madvise(buffer, size, MADV_MERGEABLE);o
> >
> > This madvise() call should fail because buffer won't be page aligned
> >
> > >                 addr =  mmap(NULL, size,
> > >                            PROT_READ | PROT_EXEC | PROT_WRITE,
> > > MAP_PRIVATE | MAP_ANONYMOUS,
> > >                            -1, 0);
> > >                 memset(addr, 0xff, size);
> > >                 ret = madvise(addr, size, MADV_MERGEABLE);
> > >                 if (ret < 0) {
> > >                         fprintf(stderr, "madvise failed: ret: %d,
> > > reason: %s\n", ret, strerror(errno));
> > >                 }
> > >                 usleep(500);
> > >         }
> > >         printf("Done....press ^C\n");
> > >
> > >         pause();
> > >
> > >         return 0;
> > > }
> > >
> > >
> > > Thanks,
> > > Pintu
> > >
> >
> > --
> > Sincerely yours,
> > Mike.
> >
> 

-- 
Sincerely yours,
Mike.