From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794764030; b=DVOfcEfViuvMWzS/RLo+nVYB/rKTUY3/rDsD1p9rU93ikp5l8sK72JK6W/yK6e1eVAJg V/LxDcfisnw8bg2MC3NVpqLhsaXTw7PvnCNzLl01AeCS9dUKpXgf5g8TPXYPELh6rCvNk F3TyznUCunebrK61KbzsOdHtD4+YDJX3P9CqbLkGKjQ3zU4MYEcwjHRO5jx9JbUEBIeaa kdRrxlufc3OPNfMA4tV++/7N6KKRaG1wL5hSLjxiZUoSvg6HNdwdrCSmuapjn0Ct3mFb0 2Kk39gX1PY5sMUhiPs5Br9eu+Rge18UQx7JC97JfY5UPInx4lYZbQJc9ThzYwotgvSg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794764030; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=oGZSQK36dQO1d5WmaeXJ05lPFIpl1QQYBwK+/5+t2vQ=; b=sdUj8DeZWhqE5aUxmpbqhEp6KSBo/EkH5h92f91JtZLkqVTJhnzqeNzfj61o2BwUdWmi yetbTw8DUgjXm+57ZM/nb5Gi4OU7qi/4x/F901n6TXrqjcqpdu077Ua7iv/+Rx2EvY2EQ 95RE8aQB/XQUjtBPNPdj63rEtvimCO9X1hI7rEq4sUnBwdYCGWb/byQjTmGQuDHCGOmbL dwQ7+0mmA64YKJWHnidPfWxwEwOTx1XeEeRcuiMbgzr+ZXH76s9HnGtxonixQYrhwFVzH SvHYs+GSXvGF1AcmU4KakAgvhMdTklzRl8YQwG04Iq1rmHhySv1bhHeMX+UlC/H40Nw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=A1EuXLLm; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C4FFE606A31A; Sun, 15 Nov 2026 17:33:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=A1EuXLLm Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1DAB91F000C4; Sun, 15 Nov 2026 17:33:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794764030; bh=oGZSQK36dQO1d5WmaeXJ05lPFIpl1QQYBwK+/5+t2vQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=A1EuXLLmgt9jXZn2tSu3WzLjEbZru4Lcta2QCZYFNqTUj0Zah/bIhU5rNG6q5iby2 S5JWxRB6HxLhaBMdF/px4nMxQXtcwZmvommDDJGFYcbroMNZgakb7tWLKL5t6Bcnuq LnezLGbUFkNd2L2hqZ54EjeGEqQ/g057yYHc3kdPemIyCqAmfU/gBnyBmOdYwpnkP7 q8J4CJtNZdQMoYaArjtUHNmyOSWwRUIgxFVrHfK6WPGNlk00If5pDJS3nqpnv4yv2P DYKvJ1jQ9DHtk3hArDac4OYuyiQmoddZSjfBoAS0WPNT+aiV8DfAuGpBPBCNVTFrdQ Hy6XkPeBAQLpQ== From: SJ Park To: David Carlier Cc: SJ Park , Aveline Noir , Andrew Morton , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 4/9] mm/damon/stat: avoid 32-bit overflow in idle percentiles Date: Sun, 15 Nov 2026 09:33:42 -0800 Message-ID: <20261115173343.82437-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261114181034.2665113-1-devnexen@gmail.com> References: X-Mailing-List: damon@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hello David, On Sat, 14 Nov 2026 18:10:34 +0000 David Carlier wrote: > Hi SJ, Aveline, > > The value stored a few lines below has the same problem on 32-bit: > > damon_stat_idletime(region) * > (long)c->attrs.aggr_interval / USEC_PER_MSEC; > > The product is the region's idle time in microseconds, held in a 32-bit > long, so it wraps once a region has been idle for more than about 36 > minutes, whatever the intervals are. The cold-end percentiles then come > out negative or wrong. Doing the multiply in s64 with div_s64() would > keep the sign and avoid it. > > Hope it helps ! Yes, this is helpful. Thank you for sharing. Would you like to send a patch for this issue? Thanks, SJ [...]