Re: [LTP] [PATCH] Set tunable value of min_free_kbytes lower

[Zhouping Liu <zliu@redhat.com>]

----- Original Message -----
> From: "Zhouping Liu" <zliu@redhat.com>
> To: "shuang qiu" <shuang.qiu@oracle.com>
> Cc: ltp-list@lists.sourceforge.net
> Sent: Monday, August 27, 2012 1:16:45 PM
> Subject: Re: [LTP] [PATCH] Set tunable value of min_free_kbytes lower
> 
> 
> 
> ----- Original Message -----
> > From: "Zhouping Liu" <zliu@redhat.com>
> > To: "shuang qiu" <shuang.qiu@oracle.com>
> > Cc: ltp-list@lists.sourceforge.net
> > Sent: Friday, August 24, 2012 4:11:41 PM
> > Subject: Re: [LTP] [PATCH] Set tunable value of min_free_kbytes
> > lower
> > 
> > 
> > 
> > ----- Original Message -----
> > > From: "shuang qiu" <shuang.qiu@oracle.com>
> > > To: ltp-list@lists.sourceforge.net
> > > Sent: Thursday, August 23, 2012 2:43:01 PM
> > > Subject: [LTP] [PATCH] Set tunable value of min_free_kbytes lower
> > > 
> > > From: Shuang Qiu <shuang.qiu@oracle.com>
> > > 
> > > The value of min_free_kbytes is set too high(half of mem_free)
> > > during
> > > testing min_free_kbytes tunable.It often cause the system to
> > > become
> > > out-of-memory.Using 20% of mem_free to avoid oom and system hang.
> > 
> > Hi, shuang
> > 
> > I met the issue that min_free_kbytes caused system hang before, and
> > what you said made sense.
> 
> For the issue that min_free_kbytes caused system hang, I prepared a
> patch for it,
> at the same time, in order to enlarge the case's coverage, I add a
> new case(2x default_tune)
> I have tested it in my box, it's good.
> 
> Shuang, can you review and test the patch?
> 
> diff --git a/testcases/kernel/mem/tunable/min_free_kbytes.c
> b/testcases/kernel/mem/tunable/min_free_kbytes.c
> index 00ead04..ded0e45 100644
> --- a/testcases/kernel/mem/tunable/min_free_kbytes.c
> +++ b/testcases/kernel/mem/tunable/min_free_kbytes.c
> @@ -10,7 +10,8 @@
>   * the current free memory with the tunable value repeatedly.
>   *
>   * a) default min_free_kbytes with all overcommit memory policy
> - * b) half of mem_free with all overcommit memory policy
> + * b) 2x default value with all overcommit memory policy
> + * c) 10% of MemFree or %5 MemTotal with all overcommit memory

Hi, Shuang

after setting 10% of MemFree or 5% MemTotal, it still cause a system
hang, which has 16Gb memory. so I adjusted the value, reduced the value
to 5% of MemFree or 2% MemTotal, which I think is more reasonable.

Thanks,
Zhouping

> policy
>   *
>   ********************************************************************
>   * Copyright (C) 2012 Red Hat, Inc.
> @@ -115,20 +116,27 @@ int main(int argc, char *argv[])
>  static void test_tune(unsigned long overcommit_policy)
>  {
>         int status;
> -       int pid[2];
> +       int pid[3];
>         int ret, i;
> -       unsigned long tune, memfree;
> +       unsigned long tune, memfree, memtotal;
>  
>         set_sys_tune("overcommit_memory", overcommit_policy, 1);
>  
> -       for (i = 0; i < 2; i++) {
> +       for (i = 0; i < 3; i++) {
>                 /* case1 */
>                 if (i == 0)
>                         set_sys_tune("min_free_kbytes", default_tune,
>                         1);
>                 /* case2 */
> -               else {
> +               else if (i == 1) {
> +                       set_sys_tune("min_free_kbytes", 2 *
> default_tune, 1);
> +               /* case3 */
> +               } else {
>                         memfree = read_meminfo("MemFree:");
> -                       tune = memfree / 2;
> +                       memtotal = read_meminfo("MemTotal:");
> +                       tune = memfree / 10;
> +                       if (tune > (memtotal / 20))
> +                               tune = memtotal / 20;
> +
>                         set_sys_tune("min_free_kbytes", tune, 1);
>                 }
>  
> 
> 
> > 
> > but after tested the patch, I found it still make the system hang
> > with the patch, so I don't think
> > this patch can fix the issue completely, maybe there are other
> > factors, or need lower tune value.
> > always suppose it was because of the high tune value, it's more
> > better to add an optional to control it.
> > also I will investigate it deeper to look after the real reason.
> > please comment if you have other ideas.
> > 
> > Thanks,
> > Zhouping
> > 
> > > ---
> > >  testcases/kernel/mem/tunable/min_free_kbytes.c |    2 +-
> > >  1 files changed, 1 insertions(+), 1 deletions(-)
> > > 
> > > diff --git a/testcases/kernel/mem/tunable/min_free_kbytes.c
> > > b/testcases/kernel/mem/tunable/min_free_kbytes.c
> > > index 00ead04..8a03f85 100644
> > > --- a/testcases/kernel/mem/tunable/min_free_kbytes.c
> > > +++ b/testcases/kernel/mem/tunable/min_free_kbytes.c
> > > @@ -128,7 +128,7 @@ static void test_tune(unsigned long
> > > overcommit_policy)
> > >  		/* case2 */
> > >  		else {
> > >  			memfree = read_meminfo("MemFree:");
> > > -			tune = memfree / 2;
> > > +			tune = memfree / 5;
> > >  			set_sys_tune("min_free_kbytes", tune, 1);
> > >  		}
> > >  
> > > --
> > > 1.7.7
> > > 
> > > 
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> 
> --
> Thanks,
> Zhouping
> 

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