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

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

Hi Li, 
Have a question about using macro SAFE_READ_MEMINFO get MemAvailable value,
Some old kernels maybe not privode "MemAvailable" field, which will broken.

 
From: Li Wang
Date: 2021-01-27 12:27
To: Xinpeng Liu
CC: LTP List
Subject: Re: [LTP] [PATCH 1/2] syscalls/ioctl: ioctl_sg01.c: ioctl_sg01 invoked oom-killer
Hi Xinpeng,

On Wed, Jan 27, 2021 at 11:28 AM Xinpeng Liu <liuxp11@chinatelecom.cn> wrote:
Kernel version is 5.4.81+,the available RAM is less than free,as follow:
[root@liuxp mywork]# head /proc/meminfo
MemTotal:       198101744 kB
MemFree:        189303148 kB
MemAvailable:   188566732 kB

So use available RAM to avoid OOM killer.

Signed-off-by: Xinpeng Liu <liuxp11@chinatelecom.cn>
---
 lib/tst_memutils.c | 29 ++++++++++++++++++++++++++---
 1 file changed, 26 insertions(+), 3 deletions(-)

diff --git a/lib/tst_memutils.c b/lib/tst_memutils.c
index dd09db4..21df9a8 100644
--- a/lib/tst_memutils.c
+++ b/lib/tst_memutils.c
@@ -10,14 +10,33 @@

 #define TST_NO_DEFAULT_MAIN
 #include "tst_test.h"
+#include "tst_safe_stdio.h"

 #define BLOCKSIZE (16 * 1024 * 1024)

+static unsigned long get_available_ram(void)
+{
+       char buf[60]; /* actual lines we expect are ~30 chars or less */
+       unsigned long available_kb = 0;
+       FILE *fp;
+
+       fp = SAFE_FOPEN("/proc/meminfo","r");
+       while (fgets(buf, sizeof(buf), fp)) {
+               if (sscanf(buf, "MemAvailable: %lu %*s\n", &available_kb) == 1){
+                       break;
+               }
+       }
+       SAFE_FCLOSE(fp);
+
+       return 1024 * available_kb;
+}
+
 void tst_pollute_memory(size_t maxsize, int fillchar)
 {
        size_t i, map_count = 0, safety = 0, blocksize = BLOCKSIZE;
        void **map_blocks;
        struct sysinfo info;
+       unsigned long available_ram = get_available_ram();

LTP provides SAFE_READ_MEMINFO() macro to be used in /proc/meminfo reading.
See: https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/mem/swapping/swapping01.c#L85

 

        SAFE_SYSINFO(&info);
        safety = MAX(4096 * SAFE_SYSCONF(_SC_PAGESIZE), 128 * 1024 * 1024);
@@ -26,15 +45,19 @@ void tst_pollute_memory(size_t maxsize, int fillchar)
        if (info.freeswap > safety)
                safety = 0;

+       /*"MemAvailable" field maybe not exist, or freeram less than available_ram*/
+       if(available_ram == 0 || info.freeram < available_ram)
+               available_ram = info.freeram;
+
        /* Not enough free memory to avoid invoking OOM killer */
-       if (info.freeram <= safety)
+       if (available_ram <= safety)
                return;

        if (!maxsize)
                maxsize = SIZE_MAX;

-       if (info.freeram - safety < maxsize / info.mem_unit)
-               maxsize = (info.freeram - safety) * info.mem_unit;
+       if (available_ram - safety < maxsize / info.mem_unit)
+               maxsize = (available_ram - safety) * info.mem_unit;

        blocksize = MIN(maxsize, blocksize);
        map_count = maxsize / blocksize;
-- 
1.8.3.1


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-- 
Regards,
Li Wang
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