From nobody Sun Feb 8 08:48:27 2026 Received: from invmail4.hynix.com (exvmail4.skhynix.com [166.125.252.92]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 859B71CA98 for ; Wed, 28 Feb 2024 01:55:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=166.125.252.92 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709085327; cv=none; b=ndk0LNRv84ShH03nIxEMdPZJKtqqWxKIgLjaNlRXUxRbWXWmVEpIxLCLhELK42obJ+LMVLVUO/XLr36LsZa/MrlhbmVec0vUII5Sf3wEhgeKAAo647Q/Xy4sOzchtz5syscQw0wM6UqfIsl/xCP8Npeyc2lRViosKJOuCXnG8vQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709085327; c=relaxed/simple; bh=gWX6eid25B21mSNcHkDXJMfEPHC+VA3OlleXqUIRNtk=; h=From:To:Cc:Subject:Date:Message-Id; b=cjCkDIQzqZ1Lb51ys9J5ucqlOROlPn+iR20Zwc+hQMgUBtemHDBhqnql3K/WmUD+R4j6BGpgqFpjvnzFn1ni/yYnvVlbRPoRSk+F1XCxkTXfRpMPnpZ3WmLPKz1Eju/hmcBHtbVU8x52ywSH8hEDl9OPosHmoJPrUGFxvjENew8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=sk.com; spf=pass smtp.mailfrom=sk.com; arc=none smtp.client-ip=166.125.252.92 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=sk.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=sk.com X-AuditID: a67dfc5b-d6dff70000001748-61-65de927f07d1 From: Byungchul Park To: akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel_team@skhynix.com, hannes@cmpxchg.org Subject: [PATCH] mm/vmscan: simplify the calculation of fractions for SCAN_FRACT Date: Wed, 28 Feb 2024 10:55:00 +0900 Message-Id: <20240228015500.52452-1-byungchul@sk.com> X-Mailer: git-send-email 2.17.1 X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFnrEJMWRmVeSWpSXmKPExsXC9ZZnoW79pHupBo9OCljMWb+GzWL1Jl+L y7vmsFncW/Of1YHF4/Cb98wemz5NYvc4MeM3i8fnTXIBLFFcNimpOZllqUX6dglcGfPXdzMX zOCvOPu1m72BcRJPFyMnh4SAicTP1UfYYOzmvjnMIDabgLrEjRs/wWwRAVmJqX/Ps4DYzALp EpcbloPFhQUCJE6sucUOYrMIqErsudTMCGLzCphKHF35mAViprzE6g0HmCHsvawSk7+qQNiS EgdX3GCZwMi9gJFhFaNQZl5ZbmJmjoleRmVeZoVecn7uJkagz5fV/onewfjpQvAhRgEORiUe 3gt37qYKsSaWFVfmHmKU4GBWEuGVEQQK8aYkVlalFuXHF5XmpBYfYpTmYFES5zX6Vp4iJJCe WJKanZpakFoEk2Xi4JRqYAwu5Z/65Hzo/jydvg3RClPvKz1/13JlbWnkFCkxGeWs8NUl8086 V2Xc3qnNqFF8aso9z1dpFpoXdWVm+5gvjDFXL+E1vZ4rZ/sxX9AkT2Cq3PSjogq71wqHN9Ws 2ND5a529ceDhk5WTA/66Z77MU1r2Z3PC+5d9urHm/I91m1r7TrTGmCzIV2Ipzkg01GIuKk4E AAi0dVH1AQAA X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFjrFJMWRmVeSWpSXmKPExsXC5WfdrFs/6V6qwaOrnBZz1q9hs1i9ydfi 8NyTrBaXd81hs7i35j+rA6vH4TfvmT02fZrE7nFixm8Wj8UvPjB5fN4kF8AaxWWTkpqTWZZa pG+XwJUxf303c8EM/oqzX7vZGxgn8XQxcnJICJhINPfNYQax2QTUJW7c+AlmiwjISkz9e54F xGYWSJe43LAcLC4sECBxYs0tdhCbRUBVYs+lZkYQm1fAVOLoyscsEDPlJVZvOMA8gZFjASPD KkaRzLyy3MTMHFO94uyMyrzMCr3k/NxNjEAfLqv9M3EH45fL7ocYBTgYlXh4L965myrEmlhW XJl7iFGCg1lJhFdGECjEm5JYWZValB9fVJqTWnyIUZqDRUmc1ys8NUFIID2xJDU7NbUgtQgm y8TBKdXAmLP43r6tf7Nj5J5XzVj3ds9chYrNaZkuUiUNcUdWnpt1vqz72c6zr99/UNhYdodl ihT3tO9Xrha8UkldwROir5z3YM+Js0dD+Liuiu0/0fM+uun3O9MtVw3+m587mHv927Rfy7l2 1q9Kq7QXSa0/c8TVwuWZ/43DxgdWhFVuPDLVSuADs/CR9UeVWIozEg21mIuKEwHr9n3w3QEA AA== X-CFilter-Loop: Reflected Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" The current way to calculate fractions for SACN_FRACT is little readable and more complicated than it should be. It also performs unnecessary division and adjustment to avoid zero operands. Prune away by multiplying the fractions by 'anon_cost * file_cost / (3 * total_cost)': where: total_cost =3D sc->anon_cost + sc->file_cost anon_cost =3D total_cost + sc->anon_cost file_cost =3D total_cost + sc->file_cost before: fraction[0] =3D swappiness * 3 * total_cost / anon_cost fraction[1] =3D (200 - swappiness) * 3 * total_cost / file_cost after: fraction[0] =3D swappiness * file_cost fraction[1] =3D (200 - swappiness) * anon_cost Worth noting that this patch doesn't change the formula. Signed-off-by: Byungchul Park --- mm/vmscan.c | 14 +++----------- 1 file changed, 3 insertions(+), 11 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 4657440854db..7b33fcc1cbdc 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2339,7 +2339,6 @@ static void get_scan_count(struct lruvec *lruvec, str= uct scan_control *sc, u64 fraction[ANON_AND_FILE]; u64 denominator =3D 0; /* gcc */ enum scan_balance scan_balance; - unsigned long ap, fp; enum lru_list lru; =20 /* @@ -2416,17 +2415,10 @@ static void get_scan_count(struct lruvec *lruvec, s= truct scan_control *sc, total_cost =3D sc->anon_cost + sc->file_cost; anon_cost =3D total_cost + sc->anon_cost; file_cost =3D total_cost + sc->file_cost; - total_cost =3D anon_cost + file_cost; =20 - ap =3D swappiness * (total_cost + 1); - ap /=3D anon_cost + 1; - - fp =3D (200 - swappiness) * (total_cost + 1); - fp /=3D file_cost + 1; - - fraction[0] =3D ap; - fraction[1] =3D fp; - denominator =3D ap + fp; + fraction[0] =3D swappiness * file_cost; + fraction[1] =3D (200 - swappiness) * anon_cost; + denominator =3D fraction[0] + fraction[1]; out: for_each_evictable_lru(lru) { int file =3D is_file_lru(lru); --=20 2.17.1