[LTP] [PATCH] mem/oom: remove non-existent case OVERCOMMIT from oom()

[Han Pingtian <hanpt@linux.vnet.ibm.com>]

On Fri, Jan 08, 2016 at 02:42:18AM -0500, Jan Stancek wrote:
> 
> 
> 
> 
> ----- Original Message -----
> > From: "Han Pingtian" <hanpt@linux.vnet.ibm.com>
> > To: "Jan Stancek" <jstancek@redhat.com>
> > Cc: ltp@lists.linux.it
> > Sent: Friday, 8 January, 2016 7:59:41 AM
> > Subject: Re: [LTP] [PATCH] mem/oom: remove non-existent case OVERCOMMIT from oom()
> > 
> > On Thu, Jan 07, 2016 at 06:57:20AM -0500, Jan Stancek wrote:
> > > 
> > > 
> > > ----- Original Message -----
> > > > From: "Han Pingtian" <hanpt@linux.vnet.ibm.com>
> > > > To: ltp@lists.linux.it
> > > > Sent: Monday, 28 December, 2015 8:49:19 AM
> > > > Subject: [LTP] [PATCH] mem/oom: remove non-existent case OVERCOMMIT from
> > > > 	oom()
> > > > 
> > > > Looks like there is no such a case "OVERCOMMIT" in oom(), so we can just
> > > > remove it.
> > > > 
> > > > Signed-off-by: Han Pingtian <hanpt@linux.vnet.ibm.com>
> > > 
> > > Reviewed-by: Jan Stancek <jstancek@redhat.com>
> > > 
> > > Looks good to me, regards,
> > > Jan
> > > 
> > Hi Jan,
> > 
> > Thanks for reviewing! I have another question: I think when
> > "overcommit_memory" being set to 1, mmap() will always succeed. It's
> > that correct? I read the code of kernel, looks like in
> > __vm_enough_memory(), if sysctl_overcommit_memory == OVERCOMMIT_ALWAYS,
> > it will always return 0. So I think in oom01.c, we should call the
> > testoom() as testoom(0, 0, 0, 1).
> 
> It can also fail if you reach max_map_count (or if map size is too big, but
> that shouldn't be the case in this test).
> 
> This is current call in oom01:
>   testoom(0, 0, ENOMEM, 1);
> 
> Third parameter (retcode) does not apply only to mmap().
> If you look at testoom(), it makes 3 tests:
>   oom(NORMAL, lite, retcode, allow_sigkill);
>   oom(MLOCK, lite, retcode, allow_sigkill);
>   oom(KSM, lite, retcode, allow_sigkill);
> 
> oom() compares that retcode to exit code of alloc_mem(),
> which will exit when either of these 3 fails: mmap, mlock or madvise.
> 
Got it and thanks! I didn't know there is a vm.max_map_count.