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 0AE53CAC5B0 for ; Sat, 4 Oct 2025 03:08:54 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2788A8E000A; Fri, 3 Oct 2025 23:08:54 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 24F328E0002; Fri, 3 Oct 2025 23:08:54 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 18BF98E000A; Fri, 3 Oct 2025 23:08:54 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 0894B8E0002 for ; Fri, 3 Oct 2025 23:08:54 -0400 (EDT) Received: from smtpin20.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id A173C1DFF16 for ; Sat, 4 Oct 2025 03:08:53 +0000 (UTC) X-FDA: 83958949746.20.F8B89B9 Received: from out-187.mta1.migadu.com (out-187.mta1.migadu.com [95.215.58.187]) by imf10.hostedemail.com (Postfix) with ESMTP id CB9F5C000D for ; Sat, 4 Oct 2025 03:08:51 +0000 (UTC) Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=bi1E45ly; spf=pass (imf10.hostedemail.com: domain of lance.yang@linux.dev designates 95.215.58.187 as permitted sender) smtp.mailfrom=lance.yang@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1759547332; 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=VH7Jum0STCRvqZ+0XX5TR3xWpnSLpgoUkMhO7MpcgEk=; b=W9UuF6jSxksBxU5RcQxEBAq0B7iJl12gyn5J2bCdmYaikzqke38p5FGiQz/gcFT+9ue9rQ 32lWVJB+YJhLHq2YpTalgHvlA4Ip4dSaQc28pGEhyIV8NtWerUMp92jD/5f6btY27G44oa zrGEs35eQYyoQevIgUT6nMvtpi8iZOk= ARC-Authentication-Results: i=1; imf10.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=bi1E45ly; spf=pass (imf10.hostedemail.com: domain of lance.yang@linux.dev designates 95.215.58.187 as permitted sender) smtp.mailfrom=lance.yang@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1759547332; a=rsa-sha256; cv=none; b=J/0F+NchNrBcXQ2i6JGGajkK87Ydg5UyboC/Z5M2BTv2abe+The3Miim84UNjFxmQpjOt/ G0Y7Pe9is5VQg3X3ASzLWBNfoa5kSwTTNevIuQQhrsr7qDUN6OZFpuCLjOsGORR9IiOf/m ZsbJVgRlnSIFSvi1KJiNcrlUuOtYiRk= Message-ID: <2ecb9ba1-8801-42b8-9575-5add856d0441@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1759547330; 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=VH7Jum0STCRvqZ+0XX5TR3xWpnSLpgoUkMhO7MpcgEk=; b=bi1E45lyAmGuMPAX85dpy4bq2sam/tjVCrywn8Xl6Pg/gGO8PIxt6apUejVSKZsxuBpjiZ mAj0a/Kzw92YoPRyG5UjziWIYipIzm3E51orNfMiAGSHg2n5jVYNim5yfMpTdqResIZwbS hgHF7dRMDgQ5SWRuOwfS0yjN33kK+Ck= Date: Sat, 4 Oct 2025 11:08:40 +0800 MIME-Version: 1.0 Subject: Re: [PATCH mm-new 1/2] mm/khugepaged: optimize PTE scanning with if-else-if-else-if chain Content-Language: en-US To: Dev Jain Cc: ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, baohua@kernel.org, lorenzo.stoakes@oracle.com, david@redhat.com, ioworker0@gmail.com, richard.weiyang@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org References: <20251002073255.14867-1-lance.yang@linux.dev> <20251002073255.14867-2-lance.yang@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Lance Yang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: CB9F5C000D X-Stat-Signature: fq57tabjz8cxt6hsew5dk9zftyxqmh4d X-HE-Tag: 1759547331-713023 X-HE-Meta: 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 IeMvf7pc khJNsSa5wVpq39ou7m1C+S8NGQ9B3UbhqrYNvJF1wBHXc9Mog4ykOv40wveo41r60/EF15ZU2EW25o4jcZ6mLADRP2YsvlXAVImyngJXyvGY3SU1bpoXwWqin8nYh75koI59qODua92ZM65bPBYokZCk79YsIaXtQQJzE8qy2uFnOLmAvBgr5CRYssLya9aSBRA7eot5JB+yeDif6ZaNjBu5TXjIGhHTMDH1NrnzMwBLTL6Yf5+4I+lkyAJAtv/9qVBqw6rRgut/Hs3utAGwg2sxgK6ebnJCHGue4YWo1EpDp2jE7Chm7KY09HSQgcIHIfIZXnwREXGumIXepTgCnDyNm7Ql5PjNOmj9O 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 2025/10/4 00:33, Dev Jain wrote: > > On 02/10/25 1:02 pm, Lance Yang wrote: >> From: Lance Yang >> >> As pointed out by Dev, the PTE checks for disjoint conditions in the >> scanning loops can be optimized. is_swap_pte, (pte_none && is_zero_pfn), >> and pte_uffd_wp are mutually exclusive. >> >> This patch refactors the loops in both __collapse_huge_page_isolate() and >> hpage_collapse_scan_pmd() to use a continuous if-else-if-else-if chain >> instead of separate if blocks. >> >> Also, this is a preparatory step to make it easier to merge the >> almost-duplicated scanning logic in these two functions, as suggested >> by David. >> >> Suggested-by: Dev Jain >> Suggested-by: David Hildenbrand >> Signed-off-by: Lance Yang >> --- >>   mm/khugepaged.c | 12 ++++-------- >>   1 file changed, 4 insertions(+), 8 deletions(-) >> >> diff --git a/mm/khugepaged.c b/mm/khugepaged.c >> index f4f57ba69d72..808523f92c7b 100644 >> --- a/mm/khugepaged.c >> +++ b/mm/khugepaged.c >> @@ -548,8 +548,7 @@ static int __collapse_huge_page_isolate(struct >> vm_area_struct *vma, >>       for (_pte = pte; _pte < pte + HPAGE_PMD_NR; >>            _pte++, addr += PAGE_SIZE) { >>           pte_t pteval = ptep_get(_pte); >> -        if (pte_none(pteval) || (pte_present(pteval) && >> -                is_zero_pfn(pte_pfn(pteval)))) { >> +        if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { > > Should have mentioned in the description that pte_present() is not required > here, so removing it. Yep, got it. > > Reviewed-by: Dev Jain Cheers, Lance > >>               ++none_or_zero; >>               if (!userfaultfd_armed(vma) && >>                   (!cc->is_khugepaged || >> @@ -560,12 +559,10 @@ static int __collapse_huge_page_isolate(struct >> vm_area_struct *vma, >>                   count_vm_event(THP_SCAN_EXCEED_NONE_PTE); >>                   goto out; >>               } >> -        } >> -        if (!pte_present(pteval)) { >> +        } else if (!pte_present(pteval)) { >>               result = SCAN_PTE_NON_PRESENT; >>               goto out; >> -        } >> -        if (pte_uffd_wp(pteval)) { >> +        } else if (pte_uffd_wp(pteval)) { >>               result = SCAN_PTE_UFFD_WP; >>               goto out; >>           } >> @@ -1316,8 +1313,7 @@ static int hpage_collapse_scan_pmd(struct >> mm_struct *mm, >>                   count_vm_event(THP_SCAN_EXCEED_SWAP_PTE); >>                   goto out_unmap; >>               } >> -        } >> -        if (pte_uffd_wp(pteval)) { >> +        } else if (pte_uffd_wp(pteval)) { >>               /* >>                * Don't collapse the page if any of the small >>                * PTEs are armed with uffd write protection.