From nobody Wed Dec 17 23:51:11 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A64DFC0015E for ; Wed, 16 Aug 2023 00:00:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240643AbjHOX7s (ORCPT ); Tue, 15 Aug 2023 19:59:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46204 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240653AbjHOX7l (ORCPT ); Tue, 15 Aug 2023 19:59:41 -0400 Received: from mail-pl1-x631.google.com (mail-pl1-x631.google.com [IPv6:2607:f8b0:4864:20::631]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2E271E74 for ; Tue, 15 Aug 2023 16:59:40 -0700 (PDT) Received: by mail-pl1-x631.google.com with SMTP id d9443c01a7336-1bdfb11ea2aso7818025ad.2 for ; Tue, 15 Aug 2023 16:59:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1692143979; x=1692748779; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=s7QZhIQhqfURcDNGbTpEX292MPIPS8rTDA+vu0krQus=; b=db2eOjTwlfITl50lWezRcdIpSLh84vwQQgQd750THy3liQ4SiKMChAfNpVedcXikRX X3zwDLdgns/fouYuEuqhbrC7A/G1dy/7btzlrPBlS1m0JFhUZ2FlGNLgnZeQhs3GcbLN iH9XMRWLoOUmNB9RS1+wfP/ri2YgWlrdruo4tfieyWVNZY3/i4RM4JYw4KjfDFvCHo2a giuqmz+6Q8wzR2IjW01L+4b6j6s8ACGSyj2+IaTaQy7q1ZSl7BSy3vCsOx7GWMX1dd5h 8sSwddTf/tGlbOLBE48nWxfaJ87p5BXXgDZge47ttBvP4dWHyckrwcmCTLFeUDBb6IS9 8fdw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1692143979; x=1692748779; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=s7QZhIQhqfURcDNGbTpEX292MPIPS8rTDA+vu0krQus=; b=SDM+xmEOuE5T5g8nN/M1hS6QpBw/EbqfMLy9za5bslxIGWBv7Nci8pYudfOo3FHbOH ZQtIOvXUa6ii49DHB51I1rZinAQrdQJUrda9DAphhmtaSyZvq7XTHrAz/Av8Xywg3Lqd 6Nf5WlvJp81iv0bA2uOQQqZezLZo441waHzWYgbZDQ12qb89cdhRiefeTB+ZlO57s2M7 5fp85sU7QvpRx1laaK06/qHz3tK6HKyRUtr6hmKcFol/FmxjIogP+DogCDvGNxQBAGxX a8w7GXIvisr92wCyxO97mFmTZger1ju8zZ6iEkNdT5q1vOzbW9/tLJl4RbOIii9qPaBQ pOzw== X-Gm-Message-State: AOJu0YzS9W8VP03WSBvJehGMejYXtDfX12d7pfLduB7P//d+0sRG6r3t hmSiH84Bhk/Z/qAMZPT2IBKOr0w358g= X-Google-Smtp-Source: AGHT+IFSqkhxeuCDdUM+8BNJp+P/b9ulNK3USHDy1k/GQGfVHUT180/M6k5NU3rzXyzb8Z9ZIqQVYA== X-Received: by 2002:a17:903:2444:b0:1bb:a7bc:37a4 with SMTP id l4-20020a170903244400b001bba7bc37a4mr481076pls.24.1692143979044; Tue, 15 Aug 2023 16:59:39 -0700 (PDT) Received: from localhost ([216.228.127.130]) by smtp.gmail.com with ESMTPSA id j7-20020a170902758700b001b9e9edbf43sm11683856pll.171.2023.08.15.16.59.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Aug 2023 16:59:38 -0700 (PDT) From: Yury Norov To: linux-kernel@vger.kernel.org Cc: Yury Norov , Andy Shevchenko , Rasmus Villemoes Subject: [PATCH] bitmap: optimize bitmap_remap() Date: Tue, 15 Aug 2023 16:59:34 -0700 Message-Id: <20230815235934.47782-1-yury.norov@gmail.com> X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" When 'new' map is empty, i.e. identity mapping, we can simply copy src to dst, which is significantly faster than setting bits one by one in a for-loop. While here, replace set_bit() with non-atomic __set_bit(). Signed-off-by: Yury Norov --- lib/bitmap.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) diff --git a/lib/bitmap.c b/lib/bitmap.c index 24284caadbcc..bf6b0eea1af8 100644 --- a/lib/bitmap.c +++ b/lib/bitmap.c @@ -1004,20 +1004,24 @@ void bitmap_remap(unsigned long *dst, const unsigne= d long *src, const unsigned long *old, const unsigned long *new, unsigned int nbits) { - unsigned int oldbit, w; + unsigned int bit, oldbit, w; =20 if (dst =3D=3D src) /* following doesn't handle inplace remaps */ return; - bitmap_zero(dst, nbits); =20 w =3D bitmap_weight(new, nbits); + if (w =3D=3D 0) { + bitmap_copy(dst, src, nbits); + return; + } + + bitmap_zero(dst, nbits); for_each_set_bit(oldbit, src, nbits) { int n =3D bitmap_pos_to_ord(old, oldbit, nbits); =20 - if (n < 0 || w =3D=3D 0) - set_bit(oldbit, dst); /* identity map */ - else - set_bit(find_nth_bit(new, nbits, n % w), dst); + bit =3D (n < 0) ? oldbit : /* identity map */ + find_nth_bit(new, nbits, n % w); + __set_bit(bit, dst); } } EXPORT_SYMBOL(bitmap_remap); --=20 2.39.2