From patchwork Fri Aug 30 05:16:09 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dev Jain X-Patchwork-Id: 13784281 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 1505FEEB7; Fri, 30 Aug 2024 05:16:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724994993; cv=none; b=tRQGqkxm4cpm6fkf8sSSeaxQOEgECmDJHIkQHJzwTCaSxHS3as9bul59F+ysJjCebJv0/oibAqWJpKCmTQiIXH09bw11ZCQyD+2dybZpbuylTFIRjWfaZ6dOD+mKl/ZZH5qHHWLND9a/vLmLi/xw28m76t1kcy89aWAJGrhu4qY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724994993; c=relaxed/simple; bh=KijCHr4lbm49o3SgoZp2sxJkChsaExW/zVUnh4L+WmQ=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=uowQbw/QVq7M+1oBcBG+pQFrqPam2mKlQDNG8iXk0W71/Qq4xz3QynXUrr0DwJvrWMspwkhJSXhdAgtkNEx/CEnrKFqx02FQ4LzJsjBurZnlPC4k1Cwt4MNt9maWtWrrS+eCf3TTCUPqa9xm7pCic4Cn96OymPOQ13/yqMbSV2o= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 270A51063; Thu, 29 Aug 2024 22:16:56 -0700 (PDT) Received: from e116581.blr.arm.com (e116581.arm.com [10.162.40.24]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 855F83F66E; Thu, 29 Aug 2024 22:16:19 -0700 (PDT) From: Dev Jain To: akpm@linux-foundation.org, shuah@kernel.org, david@redhat.com, willy@infradead.org Cc: ryan.roberts@arm.com, anshuman.khandual@arm.com, catalin.marinas@arm.com, cl@gentwo.org, vbabka@suse.cz, mhocko@suse.com, apopple@nvidia.com, osalvador@suse.de, baolin.wang@linux.alibaba.com, dave.hansen@linux.intel.com, will@kernel.org, baohua@kernel.org, ioworker0@gmail.com, gshan@redhat.com, mark.rutland@arm.com, kirill.shutemov@linux.intel.com, hughd@google.com, aneesh.kumar@kernel.org, yang@os.amperecomputing.com, peterx@redhat.com, broonie@kernel.org, mgorman@techsingularity.net, ying.huang@intel.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, Dev Jain Subject: [PATCH] selftests/mm: Relax test to fail after 100 migration failures Date: Fri, 30 Aug 2024 10:46:09 +0530 Message-Id: <20240830051609.4037834-1-dev.jain@arm.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 It was recently observed at [1] that during the folio unmapping stage of migration, when the PTEs are cleared, a racing thread faulting on that folio may increase the refcount of the folio, sleep on the folio lock (the migration path has the lock), and migration ultimately fails when asserting the actual refcount against the expected. Thereby, the migration selftest fails on shared-anon mappings. The above enforces the fact that migration is a best-effort service, therefore, it is wrong to fail the test for just a single failure; hence, fail the test after 100 consecutive failures (where 100 is still a subjective choice). Note that, this has no effect on the execution time of the test since that is controlled by a timeout. [1] https://lore.kernel.org/all/20240801081657.1386743-1-dev.jain@arm.com/ Signed-off-by: Dev Jain Suggested-by: David Hildenbrand Reviewed-by: Ryan Roberts Tested-by: Ryan Roberts --- The above patch was part of the following: https://lore.kernel.org/all/20240809103129.365029-1-dev.jain@arm.com/ I decided to send it separately since it should be applied nevertheless. tools/testing/selftests/mm/migration.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) diff --git a/tools/testing/selftests/mm/migration.c b/tools/testing/selftests/mm/migration.c index 6908569ef406..64bcbb7151cf 100644 --- a/tools/testing/selftests/mm/migration.c +++ b/tools/testing/selftests/mm/migration.c @@ -15,10 +15,10 @@ #include #include -#define TWOMEG (2<<20) -#define RUNTIME (20) - -#define ALIGN(x, a) (((x) + (a - 1)) & (~((a) - 1))) +#define TWOMEG (2<<20) +#define RUNTIME (20) +#define MAX_RETRIES 100 +#define ALIGN(x, a) (((x) + (a - 1)) & (~((a) - 1))) FIXTURE(migration) { @@ -65,6 +65,7 @@ int migrate(uint64_t *ptr, int n1, int n2) int ret, tmp; int status = 0; struct timespec ts1, ts2; + int failures = 0; if (clock_gettime(CLOCK_MONOTONIC, &ts1)) return -1; @@ -79,13 +80,17 @@ int migrate(uint64_t *ptr, int n1, int n2) ret = move_pages(0, 1, (void **) &ptr, &n2, &status, MPOL_MF_MOVE_ALL); if (ret) { - if (ret > 0) + if (ret > 0) { + /* Migration is best effort; try again */ + if (++failures < MAX_RETRIES) + continue; printf("Didn't migrate %d pages\n", ret); + } else perror("Couldn't migrate pages"); return -2; } - + failures = 0; tmp = n2; n2 = n1; n1 = tmp;