From mboxrd@z Thu Jan 1 00:00:00 1970 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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9F540E74915 for ; Wed, 24 Dec 2025 11:51:53 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D3FE36B0005; Wed, 24 Dec 2025 06:51:52 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id CEE276B0088; Wed, 24 Dec 2025 06:51:52 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BF9336B008A; Wed, 24 Dec 2025 06:51:52 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id AA2496B0005 for ; Wed, 24 Dec 2025 06:51:52 -0500 (EST) Received: from smtpin13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 50C9113902C for ; Wed, 24 Dec 2025 11:51:52 +0000 (UTC) X-FDA: 84254200464.13.7FB7930 Received: from out-189.mta1.migadu.com (out-189.mta1.migadu.com [95.215.58.189]) by imf12.hostedemail.com (Postfix) with ESMTP id 5AF4C4000F for ; Wed, 24 Dec 2025 11:51:50 +0000 (UTC) Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=bj9MAiPn; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf12.hostedemail.com: domain of lance.yang@linux.dev designates 95.215.58.189 as permitted sender) smtp.mailfrom=lance.yang@linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1766577110; a=rsa-sha256; cv=none; b=pcC/z96iK1d8IWWUg3zvahQ7rAIlfeXvuT2OEecb4QVzcW2enwNO6hC9JLIoRPBC9h/OJi YsIfFe/CA2Hy0JFwVbh937PNAtbQg8yCVE1HzAybTgO8oIGB0Zeyb5ss/wQFkc41M8C26m UCydVj7gpb9XAdu+l/1SnvjmUWkW/vg= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=bj9MAiPn; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf12.hostedemail.com: domain of lance.yang@linux.dev designates 95.215.58.189 as permitted sender) smtp.mailfrom=lance.yang@linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1766577110; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=dlj+qYNSD9ArUgWjMNVWYsSJk26ac0eHZulc973xx+A=; b=5ewMz14x/taKS0YUDzYLvAC5O0GIsaOR18dqaxu2u9nCy8q1YHqpmJP8lUN7e5saY7l203 ivZ9jTEONIZDiNhtGItn6JLe1fXBgBq2iqa3phAvBICnImodQoFpy+E6K30g7ySyeOnZjY hYsrZhPn5ItuayHTJWr1WZpCKRE8KrY= Message-ID: <6b408736-978a-4d40-adfc-97819951c3a6@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1766577108; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=dlj+qYNSD9ArUgWjMNVWYsSJk26ac0eHZulc973xx+A=; b=bj9MAiPnFohtWISNZ7PPoZ7tjLLSaTi0K1CtXYtDt3lvFPDrc6zfS39xupyWiDikLXkSuD k9yJeZSAuLxWBgul5JkeFePrADnjvQAE9q2e43ONFoemonNfka+mQpDGSE10pWT1OgKcih SzzVjy5zSySzckFTYl1o6Tfkz2SCeQo= Date: Wed, 24 Dec 2025 19:51:36 +0800 MIME-Version: 1.0 Subject: Re: [PATCH V2 2/5] mm/khugepaged: count small VMAs towards scan limit Content-Language: en-US To: Shivank Garg Cc: Zi Yan , Andrew Morton , Baolin Wang , "Liam R . Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Lorenzo Stoakes , David Hildenbrand , Barry Song , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Wei Yang References: <20251224111351.41042-4-shivankg@amd.com> <20251224111351.41042-8-shivankg@amd.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Lance Yang In-Reply-To: <20251224111351.41042-8-shivankg@amd.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: 5AF4C4000F X-Stat-Signature: qohchi1zdxiq8r4tt4hcxtbu8zs6hkdo X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1766577110-395733 X-HE-Meta: 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 DXr4h5SJ IGoysXIHnv8dc60GWRu7mT2UK42geQ5pSJptuxjmWceY+V0+xxWuBkH7+v4zcatJqeB8BrXS6Dwdx28dPv1wQGISSF5EjLeMmmx1TYtRWFHnK3lscKLagseStBhcXZ4Tqiu0QQTNKdNdXhbx0i9KfAhaS5xHpQVXWzvsFri0e9+/v3z0I6dU7vgWitMz/4bkSeQubNp3QCLrBdbxyCzZiZhN1Z0+1EGgVReLdqA/JW03/byosqaMfuWemA4XvGal6PT41UEnXOJYHzG+ShbbBwVTFtzvdiim1XzbzmsT/MALhIbJtAIwOojRvNRplhwYh5FVU9wtFluLWyAs= 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: On 2025/12/24 19:13, Shivank Garg wrote: > The khugepaged_scan_mm_slot() uses a 'progress' counter to limit the > amount of work performed and consists of three components: > 1. Transitioning to a new mm (+1). > 2. Skipping an unsuitable VMA (+1). > 3. Scanning a PMD-sized range (+HPAGE_PMD_NR). > > Consider a 1MB VMA sitting between two 2MB alignment boundaries: > > vma1 vma2 vma3 > +----------+------+----------+ > |2M |1M |2M | > +----------+------+----------+ > ^ ^ > start end > ^ > hstart,hend > > In this case, for vma2: > hstart = round_up(start, HPAGE_PMD_SIZE) -> Next 2MB alignment > hend = round_down(end, HPAGE_PMD_SIZE) -> Prev 2MB alignment > > Currently, since `hend <= hstart`, VMAs that are too small or unaligned > to contain a hugepage are skipped without incrementing 'progress'. > A process containing a large number of such small VMAs will unfairly > consume more CPU cycles before yielding compared to a process with > fewer, larger, or aligned VMAs. > > Fix this by incrementing progress when the `hend <= hstart` condition > is met. > > Additionally, change 'progress' type to `unsigned int` to match both > the 'pages' type and the function return value. > > Suggested-by: Wei Yang > Signed-off-by: Shivank Garg > --- > mm/khugepaged.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 107146f012b1..0b549c3250f9 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -2403,7 +2403,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result, > struct mm_slot *slot; > struct mm_struct *mm; > struct vm_area_struct *vma; > - int progress = 0; > + unsigned int progress = 0; > > VM_BUG_ON(!pages); > lockdep_assert_held(&khugepaged_mm_lock); > @@ -2447,7 +2447,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result, > } > hstart = round_up(vma->vm_start, HPAGE_PMD_SIZE); > hend = round_down(vma->vm_end, HPAGE_PMD_SIZE); > - if (khugepaged_scan.address > hend) { Maybe add a short comment explaining why we increment progress for small VMAs ;) Something like this: /* Count small VMAs that can't hold a hugepage towards scan limit */ > + if (khugepaged_scan.address > hend || hend <= hstart) { > progress++; > continue; > } Otherwise, looks good to me. Reviewed-by: Lance Yang