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Tue, 28 Oct 2025 14:18:19 +0800 (CST) Received: from dggpemf200018.china.huawei.com (unknown [7.185.36.31]) by mail.maildlp.com (Postfix) with ESMTPS id 9087F14027A; Tue, 28 Oct 2025 14:18:47 +0800 (CST) Received: from huawei.com (10.50.85.135) by dggpemf200018.china.huawei.com (7.185.36.31) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Tue, 28 Oct 2025 14:18:46 +0800 From: Quanmin Yan To: CC: , , , , , , Subject: [PATCH] mm/damon/stat: set last_refresh_jiffies to jiffies at startup Date: Tue, 28 Oct 2025 14:19:27 +0800 Message-ID: <20251028061927.1378746-1-yanquanmin1@huawei.com> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.50.85.135] X-ClientProxiedBy: kwepems200001.china.huawei.com (7.221.188.67) To dggpemf200018.china.huawei.com (7.185.36.31) X-Rspam-User: X-Stat-Signature: om47n8s5bpriaf4merqmtyi63uiwkda1 X-Rspamd-Queue-Id: 32256140002 X-Rspamd-Server: rspam09 X-HE-Tag: 1761632334-719066 X-HE-Meta: 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 dCHB5PRK yqSHxKUkWkUSBrwZ4/35k7yH6sQgugJ9dm3H9zu2IduDOyUpN4X6F+LOXhGnhWVfBNgEQffczn+Hjdtg+ymzlI493S7889tQYNI1rwc3/krAB+sTBZNnKqJTApxqdBZAG8JryruZq87Je1KAjYIxNm2X5N+NogObP7SZLWRq4ou5XVwOEwQ3zE/oQ0m1i4y6WFhOYrvvj+jGWIGXoZWh5bgw2Vh/BQAuXiExI8vbkaZqsM4M+USHFyOTceEP4tI/iWomDiH/Cw1HRPZgvES+uMtzdJxwafj0cikbuow+16e5kGwUQ8H0qSWk1JQ5sw5boa9srAFokBGGoMWateQ2qpkCS20hnWK8z7C2GtVdAnfyFcpVvyy+hmrQJ4LTg8mX3dBNK 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: In DAMON_STAT's damon_stat_damon_call_fn(), time_before_eq() is used to avoid unnecessarily frequent stat update. On 32-bit systems, the kernel initializes jiffies to "-5 minutes" to make jiffies wrap bugs appear earlier. However, this causes time_before_eq() in DAMON_STAT to unexpectedly return true during the first 5 minutes after boot on 32-bit systems (see [1] for more explanation, which fixes another jiffies-related issue in DAMON). As a result, DAMON_STAT does not update any monitoring results during that period, which can be more confusing when DAMON_STAT_ENABLED_DEFAULT is enabled. Fix it by setting last_refresh_jiffies to jiffies at startup. [1] https://lkml.kernel.org/r/20250822025057.1740854-1-ekffu200098@gmail.com Fixes: fabdd1e911da ("mm/damon/stat: calculate and expose estimated memory bandwidth") Signed-off-by: Quanmin Yan --- mm/damon/stat.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/damon/stat.c b/mm/damon/stat.c index 6c4503d2aee3..6dc3e18de910 100644 --- a/mm/damon/stat.c +++ b/mm/damon/stat.c @@ -132,6 +132,9 @@ static int damon_stat_damon_call_fn(void *data) struct damon_ctx *c = data; static unsigned long last_refresh_jiffies; + if (unlikely(!last_refresh_jiffies)) + last_refresh_jiffies = jiffies; + /* avoid unnecessarily frequent stat update */ if (time_before_eq(jiffies, last_refresh_jiffies + msecs_to_jiffies(5 * MSEC_PER_SEC))) -- 2.43.0