[LTP] [PATCH 1/2] syscalls/ioctl: ioctl_sg01.c: ioctl_sg01 invoked oom-killer

[liuxp11@chinatelecom.cn <liuxp11@chinatelecom.cn>]

Hi Li Wang,
I think your patch is good.
1.CommitLimit is the memory that can be allocated by application.
2.ioctl_sg01 in serveral machines with your patch,the result is passed.

Thanks!
    
From: Li Wang
Date: 2021-03-05 17:02
To: liuxp11@chinatelecom.cn
CC: Cyril Hrubis; ltp; mdoucha
Subject: Re: Re: [LTP] [PATCH 1/2] syscalls/ioctl: ioctl_sg01.c: ioctl_sg01 invoked oom-killer
Hi Xinpeng,

On Fri, Mar 5, 2021 at 1:52 PM liuxp11@chinatelecom.cn <liuxp11@chinatelecom.cn> wrote:
--- a/lib/tst_memutils.c
+++ b/lib/tst_memutils.c
@@ -36,6 +36,13 @@ void tst_pollute_memory(size_t maxsize, int fillchar)
        if (info.freeram - safety < maxsize / info.mem_unit)
                maxsize = (info.freeram - safety) * info.mem_unit;

 ==>Thanks,but the maxsize original code need to be deleted,Right?

No, the maxsize code is also useful, it needs to define the value in
most common situations(i.e. CommitLimit > MemAvailable).

But I'm still hesitating to use ComitLimit as the threshold for 'maxsize'.
Because according to the Linux document, it says that only take effort
when overcommit_memory is setting to 2. But our test system all set 0
by default.

   "This limit is only adhered to if strict overcommit accounting is enabled
    (mode 2 in 'vm.overcommit_memory')."
    see: https://github.com/torvalds/linux/blob/master/Documentation/filesystems/proc.rst

Seems to use CommitLimit looks a bit strict and strange to test.

And I even think the way to use MemAvailable is acceptable if
MemFree > MemAvailable, just like what you did in your last patch.

I'm still not very sure so far~
(But one thing I can confirm that MemAvailable < MemFree is correct behavior sometimes)

 

+       /*
+        * To respect CommitLimit to prevent test invoking OOM killer,
+        * this may appear on system with a smaller swap-disk (or disabled).
+        */
+       if (SAFE_READ_MEMINFO("CommitLimit:") < SAFE_READ_MEMINFO("MemAvailable:"))
+               maxsize = SAFE_READ_MEMINFO("CommitLimit:") * 1024 - (safety * info.mem_unit);
+
        blocksize = MIN(maxsize, blocksize);
        map_count = maxsize / blocksize;
        map_blocks = SAFE_MALLOC(map_count * sizeof(void *));
 

-- 
Regards,
Li Wang
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