[LTP] [PATCH v4] mm: rewrite mtest01 with new API

[Li Wang]

Hi Jan,

On Wed, Mar 13, 2019 at 7:48 PM Jan Stancek <jstancek@redhat.com> wrote:

> From: Li Wang <liwang@redhat.com>
>
>  Test issue:
>    mtest01 start many children to alloc chunck of memory and do write
>    page(with -w option), but occasionally some children were killed by
>    oom-killer and exit with SIGCHLD signal sending. After the parent
>    reciving this SIGCHLD signal it will report FAIL as a test result.
>
>    It seems not a real kernel bug if something just like that, it's
>    trying to use 80% of memory and swap. Once it uses most of memory,
>    system starts swapping, but the test is likely consuming memory at
>    greater rate than kswapd can provide, which eventually triggers OOM.
>
>    ---- FAIL LOG ----
>    mtest01     0  TINFO  :  Total memory already used on system = 1027392
> kbytes
>    mtest01     0  TINFO  :  Total memory used needed to reach maximum =
> 12715520 kbytes
>    mtest01     0  TINFO  :  Filling up 80% of ram which is 11688128 kbytes
>    mtest01     1  TFAIL  :  mtest01.c:314: child process exited
> unexpectedly
>    -------------------
>
>  Rewrite changes:
>    To make mtest01 more easier to understand, I just rewrite it into
>    LTP new API and make a little changes in children behavior.
>
>    * decrease the pressure to 80% of free memory for testing
>    * drop the signal SIGCHLD action becasue new API help to
> check_child_status
>    * make child pause itself after finishing their memory
> allocating/writing
>    * parent sends SIGCONT to make children continue and exit
>    * use TST_PROCESS_STATE_WAIT to wait child changes to 'T' state
>    * involve ALLOC_THRESHOLD to rework same code in defines
>    * to make mtest01 support running with -i N > 1
>
> Signed-off-by: Li Wang <liwang@redhat.com>
> Signed-off-by: Jan Stancek <jstancek@redhat.com>
> ---
> Li,
>
> I'm posting v4 because I'm proposing also couple other small changes.
> Changes in v4:
> - fix -b parameter, it was ignored, because maxpercent is always non-zero
>   Now, if -b is set, then maxpercent is ignored.
> - remove casts to unsigned long long, use literal with ULL suffix
> - pid_count renamed to children_done, because pid_count vs. pid_cntr was
> confusing
> - original_maxbytes dropped, instead alloc_maxbytes remains unchanged in
> mem_test()
> - do_write_page renamed to do_write_mem, since we write more than single
> page
> - do_write_mem loop now increases offset by page size to make it slightly
> faster
> - bytecount initialized to 0 in child_loop_alloc()
> - info messages expanded to show some timestamp (remaining time)
> - PASS/FAIL messages for do_write=0 and do_write=1 consolidated to single
> one
> - child creation loop in mem_test() tweaked:
>   - child_loop_alloc() called directly from loop
>   - pid_cntr incremented and used as index to pid_list array, 'i' variable
> not used
>   - while condition "((pid != 0)" removed, it's always true
> - sleep reduced to 100ms
> - "while (pid_list[i] > 0)" replaced with for loop, since we know exactly
> how many
>   children we spawned. memset in setup dropped.
>

I'm OK with these improvements, patch v4 looks quite good to me:).

-- 
Regards,
Li Wang
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