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Mon, 25 Mar 2024 10:24:26 +0800 Message-ID: Date: Mon, 25 Mar 2024 10:24:26 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.11.2 Subject: Re: [PATCH v2 2/2] selftest/mm: ksm_functional_tests: extend test case for ksm fork/exec To: David Hildenbrand , , , , , , , References: <20240322060947.3254967-1-tujinjiang@huawei.com> <20240322060947.3254967-3-tujinjiang@huawei.com> From: Jinjiang Tu In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.179.13] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To dggpeml500011.china.huawei.com (7.185.36.84) X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 39F38100005 X-Stat-Signature: s9emhku88ay6abp1usre93txso8hx638 X-HE-Tag: 1711333470-645955 X-HE-Meta: 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 Hr/ACIiE M6wHQrKJTae1uL8SFinIEWiv3vWPd8sfqp7mEE2qFmWb/+75y7KAedCNy1o+Y2U79si4N5Ln9iHJl5WZe1gAwAp+ZhS/cR/N/dbP9wATrtkClS3zs8En2xQbpRZbcs4wKpyuMqNMMoDsMN/0K0/Y9MdHUWo6RXOSSkGnm8Z8prJ1+x5yc3MCjqnm4FEohig+yh1qhughZc2dgOnI= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 在 2024/3/22 19:43, David Hildenbrand 写道: > On 22.03.24 07:09, Jinjiang Tu wrote: >> This extends test_prctl_fork() and test_prctl_fork_exec() to make sure >> that deduplication really happens, instead of only test the >> MMF_VM_MERGE_ANY flag is set. >> >> Signed-off-by: Jinjiang Tu >> --- >>   .../selftests/mm/ksm_functional_tests.c       | 79 +++++++++++++++++-- >>   1 file changed, 73 insertions(+), 6 deletions(-) >> >> diff --git a/tools/testing/selftests/mm/ksm_functional_tests.c >> b/tools/testing/selftests/mm/ksm_functional_tests.c >> index d615767e396b..01999aab2e37 100644 >> --- a/tools/testing/selftests/mm/ksm_functional_tests.c >> +++ b/tools/testing/selftests/mm/ksm_functional_tests.c >> @@ -146,6 +146,54 @@ static int ksm_unmerge(void) >>       return 0; >>   } >>   +static int child_test_merge(void) >> +{ >> +    const unsigned int size = 2 * MiB; >> +    char *map; >> +    int ret = -1; >> + >> +    /* Stabilize accounting by disabling KSM completely. */ >> +    if (ksm_unmerge()) { >> +        ksft_print_msg("Disabling (unmerging) KSM failed\n"); >> +        return ret; >> +    } >> + >> +    if (get_my_merging_pages() > 0) { >> +        ksft_print_msg("Still pages merged\n"); >> +        return ret; >> +    } >> + >> +    map = mmap(NULL, size, PROT_READ|PROT_WRITE, >> +           MAP_PRIVATE|MAP_ANON, -1, 0); >> +    if (map == MAP_FAILED) { >> +        ksft_print_msg("mmap() failed\n"); >> +        return ret; >> +    } >> + >> +    /* Don't use THP. Ignore if THP are not around on a kernel. */ >> +    if (madvise(map, size, MADV_NOHUGEPAGE) && errno != EINVAL) { >> +        ksft_print_msg("MADV_NOHUGEPAGE failed\n"); >> +        goto unmap; >> +    } >> + >> +    memset(map, 0x1c, size); >> + >> +    if (ksm_merge()) { >> +        ksft_print_msg("Running KSM failed\n"); >> +        goto unmap; >> +    } >> + >> +    if (get_my_merging_pages() <= 0) { >> +        ksft_print_msg("Fail to merge\n"); >> +        goto unmap; >> +    } > > Looks like all you want is use mmap_and_merge_range(), but neither > setting the prctl nor madvise(). > > Two alternatives: > > 1) switching from "bool use_prctl" to an enum like > > enum ksm_merge_mode { >     KSM_MERGE_PRCTL >     KSM_MERGE_MADVISE, >     KSM_MERGE_NONE, /* PRCTL already set */ > }; > > Then, you can simply use mmap_and_merge_range(0x1c, 2 * MiB, > PROT_READ|PROT_WRITE, KSM_MERGE_NONE); I have considered this before. But, mmap_and_merge_range() calls ksft_test_result_fail() when error occurs, ksft_test_result_fail() prints prefixed with ksft_fail count. When mmap_and_merge_range() is called in the child process, the ksft_fail isn't consisent with the parent process due to the global variable ksft_fail is CoWed. As a result, ksft_print_msg() is intended to be called in child process. Maybe, We could introduce a macro ksm_print() to control which function is called according to ksm_merge_mode : #define ksm_print(mode, fmt, ...) do {    \     if ((mode) == KSM_MERGE_NONE)                \         ksft_print_msg(fmt, ##__VA_ARGS__);\     else                        \         ksft_test_result_fail(fmt, ##__VA_ARGS__);\     } while (0) > > 2) With "bool use_prctl", before doing the prctl(PR_SET_MEMORY_MERGE, > ...), check if it is already enabled. > > As we do that already in ksm_fork_exec_child(), and fail if it isn't > set, that should work. > > Then, you can simply use mmap_and_merge_range(0x1c, 2 * MiB, > PROT_READ|PROT_WRITE, true); > > here. > >> + >> +    ret = 0; >> +unmap: >> +    munmap(map, size); >> +    return ret; >> +} >> + >>   static char *mmap_and_merge_range(char val, unsigned long size, int >> prot, >>                     bool use_prctl) >>   { >> @@ -458,7 +506,11 @@ static void test_prctl_fork(void) >>         child_pid = fork(); >>       if (!child_pid) { >> -        exit(prctl(PR_GET_MEMORY_MERGE, 0, 0, 0, 0)); >> +        if (prctl(PR_GET_MEMORY_MERGE, 0, 0, 0, 0) != 1) >> +            exit(-1); >> +        if (child_test_merge() != 0) >> +            exit(-2); >> +        exit(0); >>       } else if (child_pid < 0) { >>           ksft_test_result_fail("fork() failed\n"); >>           return; >> @@ -467,8 +519,14 @@ static void test_prctl_fork(void) >>       if (waitpid(child_pid, &status, 0) < 0) { >>           ksft_test_result_fail("waitpid() failed\n"); >>           return; >> -    } else if (WEXITSTATUS(status) != 1) { >> -        ksft_test_result_fail("unexpected PR_GET_MEMORY_MERGE result >> in child\n"); >> +    } >> + >> +    status = WEXITSTATUS(status); >> +    if (status != 0) { >> +        if (status == -1) >> +            ksft_test_result_fail("unexpected PR_GET_MEMORY_MERGE >> result in child\n"); >> +        else >> +            ksft_test_result_fail("fail to merge in child\n"); >>           return; >>       } >>   @@ -483,7 +541,13 @@ static void test_prctl_fork(void) >>   static int ksm_fork_exec_child(void) >>   { >>       /* Test if KSM is enabled for the process. */ >> -    return prctl(PR_GET_MEMORY_MERGE, 0, 0, 0, 0) == 1; >> +    if (prctl(PR_GET_MEMORY_MERGE, 0, 0, 0, 0) != 1) >> +        return -1; >> + >> +    if (child_test_merge() != 0) > > You can drop the "!=0". But maybe, you can just inline the call to > mmap_and_merge_range() here. > >> +        return -2; >> + >> +    return 0; > >