Re: [LTP] [PATCH]KSM: full_scans will stop increasing after stopping ksm

[Bian Naimeng <biannm@cn.fujitsu.com>]

Han Pingtian wrote:
> On Thu, Apr 07, 2011 at 01:52:40PM +0800, Bian Naimeng wrote:
>>
>> CAI Qian wrote:
>>> ----- Original Message -----
>>>> Qian Cai wrote:
>>>>> On 2011-4-4, at 0:47, Bian Naimeng <biannm@cn.fujitsu.com> wrote:
>>>>>
>>>>>> There are some problem in ksm tests.
>>>>>>
>>>>>> 1. We should break the test when checking is failure.
>>>>> No, this is not the intention. The design here is to run all tests
>>>>> to check for all stats to give a full picture even if the a single
>>>>> failure has been observed. This type of the failures do not prevent
>>>>> the rest of the tests from running, so there is no need to stop the
>>>>> tests now which also give more insight to track down root causes.
>>>> Various reason can make checking failure, someone can make the test
>>>> hangup.
>>>> I did this test on RHEL5, i found ksmd stopped before doing "echo 2 >
>>>> /sys/kernel/mm/ksm/run",
>>>> so group_check will be hanged on "new_num < old_num * 3".
>>>>
>>>> So, i think we should break the test if "run" is not expecting.
>>> What happened if you run the tests for a recent upstream kernel? There
>>> are some patches for ksm recently merged upstream. If the problem still
>>> persistent, please paste the EXACT OUTPUT from the ksm01 test. If it is
>>> hung, please upload sysrq-t output somewhere.
>>>
>> Maybe there are some bugs in the RHEL6's kernel, but the purpose of this patch
>> is not to workround these bugs, i want to fix the test's bug.
>>
>> Would you explain to me why we do this loop "while (new_num < old_num * 3)" in
>> group_check, i think "while (new_num < old_num + 3)" is better.
>>
>> Some time ago, the following patch insert this loop.
>> http://sourceforge.net/mailarchive/forum.php?thread_name=AANLkTi%3Dg%3DojJu0m%2B556rnekYenRTXtX%2BVBOj%3DrPmnjSw%40mail.gmail.com&forum_name=ltp-list
>>
>> The changelog of this patch said "we should wait 3~5 increments of the
>> /sys/kernel/mm/ksm/full_scans before checking ksm* testcases's results", but
>> it do "while (new_num < old_num * 3)" actually.
> I made a mistake. The code is what I wanted to do, but the changelog was
> wrong. When testing the new ksm patch, the developer told us we must
> wait 3~5 times increments of the number before checking testing
> results. So I coded to wait til new_num >= old_num * 3 before checking
> the results. 
> 

The bigger old_new is, the longer time test takes, it's strange.

> About 'echo 2 > /sys/kernel/mm/ksm/run' problem, I have tested it with
> ksm01.
> If I run the 'echo 2 > /sys/kernel/mm/ksm/run' before issue ksm test,
> the content of /sys/kernel/mm/ksm/run will be changed to 1 and the test
> can finished successfully. 

I think we shoud not care this.

> Only if I echo the 2 between the testing process,
> ksm01 will hang up. On that time, new_num will be zero, so your plus 3
> method won't work either. So what should we do in this circumstance?
> 

Please look at my patch, after stopping ksmd in the testing(echo 2 > /sys/kernel/mm/ksm/run or
echo 0 > /sys/kernel/mm/ksm/run), group_check will skip waiting at the loop "new_num >= old_num * 3".

Regards
 Bian

> Thanks.
> 
> Han Pingtian
>> Regards
>>  Bian
>>
>>> CAI Qian
>>>  
>>>>>> 2. The condition "new_num < old_num * 3" seems uncomfortable, i
>>>>>> think
>>>>>>   it should be "new_num < old_num + 3"
>>>>> I don't understand. What error did you see from the testing output?
>>>> Sometimes, the old_num is a big number, so it takes long time in this
>>>> loop,
>>>> i don't understand the purpose.
>>>> Would you explain to me why we expect this condition "new_num <
>>>> old_num * 3".
>>>>
>>>>>> 3. After stopping ksm(echo 2 > /sys/kernel/mm/ksm/run), the ksmd
>>>>>>   will stop scaning pages, so looping in "new_num < old_num * 3"
>>>>>>   is wrong.
>>>>> Ditto.
>>>>>
>>>> After stopping ksm, looping in "new_num < old_num * 3" will make the
>>>> process hang up,
>>>> because new_num does not be increased.
>>>>
>>>> Regards
>>>> Bian
>>>>
>>>>
>>>>> CAI Qian
>>>>>> Signed-off-by: Bian Naimeng <biannm@cn.fujitsu.com>
>>>>>>
>>>>>> ---
>>>>>> testcases/kernel/mem/include/mem.h | 2 +-
>>>>>> testcases/kernel/mem/lib/mem.c | 19 ++++++++++---------
>>>>>> 2 files changed, 11 insertions(+), 10 deletions(-)
>>>>>>
>>>>>> diff --git a/testcases/kernel/mem/include/mem.h
>>>>>> b/testcases/kernel/mem/include/mem.h
>>>>>> index 778d403..b640a63 100644
>>>>>> --- a/testcases/kernel/mem/include/mem.h
>>>>>> +++ b/testcases/kernel/mem/include/mem.h
>>>>>> @@ -42,7 +42,7 @@ void check(char *path, long int value);
>>>>>> void verify(char value, int proc, int start, int end, int start2,
>>>>>> int end2);
>>>>>> void group_check(int run, int pages_shared, int pages_sharing,
>>>>>>        int pages_volatile, int pages_unshared, int sleep_millisecs,
>>>>>> - int pages_to_scan);
>>>>>> + int pages_to_scan, int scans);
>>>>>> void create_same_memory(int size, int num, int unit);
>>>>>> void check_ksm_options(int *size, int *num, int *unit);
>>>>>> void write_cpusets(void);
>>>>>> diff --git a/testcases/kernel/mem/lib/mem.c
>>>>>> b/testcases/kernel/mem/lib/mem.c
>>>>>> index 12e61e9..db1a7dd 100644
>>>>>> --- a/testcases/kernel/mem/lib/mem.c
>>>>>> +++ b/testcases/kernel/mem/lib/mem.c
>>>>>> @@ -284,7 +284,7 @@ void check(char *path, long int value)
>>>>>>
>>>>>>    tst_resm(TINFO, "%s is %ld.", path, atol(buf));
>>>>>>    if (atol(buf) != value)
>>>>>> - tst_resm(TFAIL, "%s is not %ld.", path, value);
>>>>>> + tst_brkm(TFAIL, tst_exit, "%s is not %ld.", path, value);
>>>>>> }
>>>>>>
>>>>>> void verify(char value, int proc, int start, int end, int start2,
>>>>>> int end2)
>>>>>> @@ -312,7 +312,8 @@ void verify(char value, int proc, int start,
>>>>>> int end, int start2, int end2)
>>>>>>
>>>>>> void group_check(int run, int pages_shared, int pages_sharing,
>>>>>>        int pages_volatile, int pages_unshared,
>>>>>> - int sleep_millisecs, int pages_to_scan)
>>>>>> + int sleep_millisecs, int pages_to_scan,
>>>>>> + int scans)
>>>>>> {
>>>>>>    int fd;
>>>>>>    char buf[BUFSIZ];
>>>>>> @@ -332,7 +333,7 @@ void group_check(int run, int pages_shared, int
>>>>>> pages_sharing,
>>>>>>    old_num = new_num = atoi(buf);
>>>>>>    if (lseek(fd, 0, SEEK_SET) == -1)
>>>>>>        tst_brkm(TBROK|TERRNO, cleanup, "lseek");
>>>>>> - while (new_num < old_num * 3) {
>>>>>> + while (new_num < old_num + scans) {
>>>>>>        sleep(1);
>>>>>>        if (read(fd, buf, BUFSIZ) < 0)
>>>>>>            tst_brkm(TBROK|TERRNO, cleanup, "read");
>>>>>> @@ -587,7 +588,7 @@ void create_same_memory(int size, int num, int
>>>>>> unit)
>>>>>>        if (kill(child[k], SIGCONT) == -1)
>>>>>>            tst_brkm(TBROK|TERRNO, cleanup, "kill child[%d]", k);
>>>>>>    }
>>>>>> - group_check(1, 2, size * num * 256 - 2, 0, 0, 0, size * 256 *
>>>>>> num);
>>>>>> + group_check(1, 2, size * num * 256 - 2, 0, 0, 0, size * 256 *
>>>>>> num, 3);
>>>>>>
>>>>>>    tst_resm(TINFO, "wait for child 1 to stop.");
>>>>>>    if (waitpid(child[1], &status, WUNTRACED) == -1)
>>>>>> @@ -599,7 +600,7 @@ void create_same_memory(int size, int num, int
>>>>>> unit)
>>>>>>    tst_resm(TINFO, "resume child 1.");
>>>>>>    if (kill(child[1], SIGCONT) == -1)
>>>>>>        tst_brkm(TBROK|TERRNO, cleanup, "kill");
>>>>>> - group_check(1, 3, size * num * 256 - 3, 0, 0, 0, size * 256 *
>>>>>> num);
>>>>>> + group_check(1, 3, size * num * 256 - 3, 0, 0, 0, size * 256 *
>>>>>> num, 3);
>>>>>>
>>>>>>    tst_resm(TINFO, "wait for child 1 to stop.");
>>>>>>    if (waitpid(child[1], &status, WUNTRACED) == -1)
>>>>>> @@ -613,7 +614,7 @@ void create_same_memory(int size, int num, int
>>>>>> unit)
>>>>>>        if (kill(child[k], SIGCONT) == -1)
>>>>>>            tst_brkm(TBROK|TERRNO, cleanup, "kill child[%d]", k);
>>>>>>    }
>>>>>> - group_check(1, 1, size * num * 256 - 1, 0, 0, 0, size * 256 *
>>>>>> num);
>>>>>> + group_check(1, 1, size * num * 256 - 1, 0, 0, 0, size * 256 *
>>>>>> num, 3);
>>>>>>
>>>>>>    tst_resm(TINFO, "wait for all children to stop.");
>>>>>>    for (k = 0; k < num; k++) {
>>>>>> @@ -627,7 +628,7 @@ void create_same_memory(int size, int num, int
>>>>>> unit)
>>>>>>    tst_resm(TINFO, "resume child 1.");
>>>>>>    if (kill(child[1], SIGCONT) == -1)
>>>>>>        tst_brkm(TBROK|TERRNO, cleanup, "kill");
>>>>>> - group_check(1, 1, size * num * 256 - 2, 0, 1, 0, size * 256 *
>>>>>> num);
>>>>>> + group_check(1, 1, size * num * 256 - 2, 0, 1, 0, size * 256 *
>>>>>> num, 3);
>>>>>>
>>>>>>    tst_resm(TINFO, "wait for child 1 to stop.");
>>>>>>    if (waitpid(child[1], &status, WUNTRACED) == -1)
>>>>>> @@ -647,7 +648,7 @@ void create_same_memory(int size, int num, int
>>>>>> unit)
>>>>>>        tst_brkm(TBROK|TERRNO, cleanup, "open");
>>>>>>    if (write(fd, "2", 1) != 1)
>>>>>>        tst_brkm(TBROK|TERRNO, cleanup, "write");
>>>>>> - group_check(2, 0, 0, 0, 0, 0, size * 256 * num);
>>>>>> + group_check(2, 0, 0, 0, 0, 0, size * 256 * num, 0);
>>>>>>
>>>>>>    tst_resm(TINFO, "wait for all children to stop.");
>>>>>>    for (k = 0; k < num; k++) {
>>>>>> @@ -668,7 +669,7 @@ void create_same_memory(int size, int num, int
>>>>>> unit)
>>>>>>    if (write(fd, "0", 1) != 1)
>>>>>>        tst_brkm(TBROK|TERRNO, cleanup, "write");
>>>>>>    close(fd);
>>>>>> - group_check(0, 0, 0, 0, 0, 0, size * 256 * num);
>>>>>> + group_check(0, 0, 0, 0, 0, 0, size * 256 * num, 0);
>>>>>>    while (waitpid(-1, &status, WUNTRACED | WCONTINUED) > 0)
>>>>>>        if (WEXITSTATUS(status) != 0)
>>>>>>            tst_resm(TFAIL, "child exit status is %d",
>>>>>> --
>>>>>> 1.7.1
>>>>>>
>>>>>>
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>>
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> 


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