From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 71ECC37D113; Thu, 25 Jun 2026 14:24:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782397491; cv=none; b=cfjP7/1r/5mFtKuLRwApz3HK519Q+WQvS4frpT5K2ty2ugVt0dokORPGPkegktW7yXdSF7Q3tG3WamTV7JqCC0uMlNn2q3pJwDXJ95CvFjJ/+sczW7kStSwvu3RJzWdG6fZlzd6H0hpZvdAdSw9GpiiClPrQtOB0cMRwflaVp3w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782397491; c=relaxed/simple; bh=3kFNcksddTMoPl6d1RNPtllzhSXlxi+x+OM5EDF9YpY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Su0jsr5qD++Iv7C35OZiCV5rgKCqWW4UU5wpfTQjtdL2qCdvK6fXW8jaYw9i67sXzKBEC9R0KTW/OsYVtoVNCrGWKObeQLE9sioWWx+TaP1yXJLeZ/OOcl0uaNx2BgY33iHZGXeQx1DdWvgGyAY9PIQJHbVG12migFibT55Vijc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=kdAoFumM; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="kdAoFumM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A8C441F00A3E; Thu, 25 Jun 2026 14:24:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782397490; bh=HI/zoVaSGKDNLoA6cct9QoJPib3MnUiHJc9KJcrjGCA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=kdAoFumMFmi8lT19UnVawdo/dF2kT1jrR8Zpwb1bBDvnk5ceyRoTQhg8gVQjibl0d lIPsINw6UFSNllBr8tHQs4ab+lrffozZWkxzXV35ueEto6mG27HfvKwuDg0W+ZjIoE xnVqQY03+pDWmkQef7urPe5XGKmBDsnhH09Uahn+MI1CiC1FH+/jI8Y4rf5hZHPj+e TYnyYPdax/RtAbWo+IZ2uOWYL6cacsu3n/Cnn3SqprbSP5phS6I7TulDGAUIDsy8fB rrX/QxRE/1Dr0V3zLrJfOuZ/DEM8M1aKecVwQAVDPB31xD/VAp1DrgNBhoPAVk1wu0 2RUGOhCnRndoA== From: SeongJae Park To: Cc: SeongJae Park , Andrew Morton , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [RFC PATCH v1.2 08/11] mm/damon/core: reduce range setup in damon_commit_target_regions() Date: Thu, 25 Jun 2026 07:23:53 -0700 Message-ID: <20260625142357.103500-9-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260625142357.103500-1-sj@kernel.org> References: <20260625142357.103500-1-sj@kernel.org> Precedence: bulk X-Mailing-List: damon@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit damon_commit_target_regions() calls damon_set_regions() for updating the destination target's monitoring target region boundaries. It sets the boundaries same to source target's monitoring regions, even if they are adjacent. Meanwhile, damon_set_region() sets the destination target regions exactly the same to the source, only when the target regions are empty. When there are existing target regions, only a few regions are expanded or shrunk to fit on only the boundaries for disjoint regions in the source. Hence the adjacent source ranges mean nothing in common cases. When there are many regions, such adjacent range setup is only a waste of time and space. We recently found [1] it is actually causing memory overhead. Setup the ranges for only distinct ranges. [1] https://lore.kernel.org/20260603112306.58490-1-akinobu.mita@gmail.com Signed-off-by: SeongJae Park --- mm/damon/core.c | 22 +++++++++++++++++----- 1 file changed, 17 insertions(+), 5 deletions(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index 7e4b9affc5b06..ce5294cb1b4f3 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -1349,21 +1349,33 @@ static struct damon_target *damon_nth_target(int n, struct damon_ctx *ctx) static int damon_commit_target_regions(struct damon_target *dst, struct damon_target *src, unsigned long src_min_region_sz) { - struct damon_region *src_region; + struct damon_region *src_region, *prev = NULL; struct damon_addr_range *ranges; int i = 0, err; - damon_for_each_region(src_region, src) - i++; + damon_for_each_region(src_region, src) { + if (!prev || prev->ar.end != src_region->ar.start) + i++; + prev = src_region; + } if (!i) return 0; ranges = kmalloc_objs(*ranges, i, GFP_KERNEL | __GFP_NOWARN); if (!ranges) return -ENOMEM; + prev = NULL; i = 0; - damon_for_each_region(src_region, src) - ranges[i++] = src_region->ar; + damon_for_each_region(src_region, src) { + if (!prev) { + ranges[i].start = src_region->ar.start; + } else if (prev->ar.end != src_region->ar.start) { + ranges[i++].end = prev->ar.end; + ranges[i].start = src_region->ar.start; + } + prev = src_region; + } + ranges[i++].end = damon_last_region(src)->ar.end; err = damon_set_regions(dst, ranges, i, src_min_region_sz); kfree(ranges); return err; -- 2.47.3