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 F1ED6E6E807 for ; Tue, 3 Feb 2026 11:23:56 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 098D66B0088; Tue, 3 Feb 2026 06:23:56 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 070F76B0089; Tue, 3 Feb 2026 06:23:56 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F0A276B008C; Tue, 3 Feb 2026 06:23:55 -0500 (EST) 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 DD2F66B0088 for ; Tue, 3 Feb 2026 06:23:55 -0500 (EST) Received: from smtpin04.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 905F114042F for ; Tue, 3 Feb 2026 11:23:55 +0000 (UTC) X-FDA: 84402910830.04.B2B7821 Received: from out-183.mta1.migadu.com (out-183.mta1.migadu.com [95.215.58.183]) by imf25.hostedemail.com (Postfix) with ESMTP id 8D6BDA000C for ; Tue, 3 Feb 2026 11:23:53 +0000 (UTC) Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=wYNSiW0k; spf=pass (imf25.hostedemail.com: domain of lance.yang@linux.dev designates 95.215.58.183 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=1770117833; 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=Z9CK+57gyxylgnXvGgZfYQ4gb8NRQ2Dah27jPVjSsr8=; b=OibSJe8Mot7L/F430jEzjzooer0a8CQD1Y0M1brdNhFJqn/bUr5bmf55HWWgJcreFGtPKy 9EFza7esxcwajnLTdETmzi2xpRgVlAwwwBBFyllpxFT/sYNtPctA9UXke0ezpOAuatbYhy Vi0LSxzyXlpS8mCY/mL4ZfKM/dDRxlw= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=wYNSiW0k; spf=pass (imf25.hostedemail.com: domain of lance.yang@linux.dev designates 95.215.58.183 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=1770117833; a=rsa-sha256; cv=none; b=Kzy6aKGKLgXmH/JkrA4wx+eUGG0yh8fZDdPnqPG7vT9UuURXVS/kPzX42Qt+4ONd2bKp3m hfMh1g9AccOANRF+R/udPyzn1ECcWvIGl2bez4DYeXYcJdRRcbwLdw2r7KQPdJ28hxGiQG uOMjR8HZvMpT1MFeTZpbIJSDBrMEMss= Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1770117831; 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=Z9CK+57gyxylgnXvGgZfYQ4gb8NRQ2Dah27jPVjSsr8=; b=wYNSiW0kBXQX8yk5biXw6LHBuV/0KwMr2Pj06sAg+HuMQvrtu/cKznpSKwYWvOk/1d+dQd fUqmP+DskKb1Zhw+z6hqs8omWok74WNmVXbOpJpdQqGNY22pTyyJO9iASp2CdGsfTyd7I3 Ack+v+N3Y0KJP+xDcQk5jxPwd5LXlts= Date: Tue, 3 Feb 2026 19:23:39 +0800 MIME-Version: 1.0 Subject: Re: [PATCH mm-new v6 4/5] mm: khugepaged: skip lazy-free folios Content-Language: en-US To: Vernon Yang Cc: lorenzo.stoakes@oracle.com, ziy@nvidia.com, dev.jain@arm.com, baohua@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Vernon Yang , david@kernel.org, akpm@linux-foundation.org References: <20260201122554.1470071-1-vernon2gm@gmail.com> <20260201122554.1470071-5-vernon2gm@gmail.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Lance Yang In-Reply-To: <20260201122554.1470071-5-vernon2gm@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 8D6BDA000C X-Stat-Signature: tnkuxyyhqt5kr1ho1zpdyxyz4soj8a7o X-Rspam-User: X-HE-Tag: 1770117833-882657 X-HE-Meta: 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 ziQCG9BG dLxrjHWf7Ai3jKWgX9WP+A1JjjzV4sxroBh3rgpQxIdQGNLu28aUOydoto+DN8xN+j/9dQdMWTNKi6AhRWlNb0iCVK50Km5gfSqkxTkjjA9x3YfCIy8vA+afC39q02XvLF671rrgvL4maj4GQGJZwPvgvoHb/IVp//FlCp0aStjiHMUE= 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 2026/2/1 20:25, Vernon Yang wrote: > From: Vernon Yang > > For example, create three task: hot1 -> cold -> hot2. After all three > task are created, each allocate memory 128MB. the hot1/hot2 task > continuously access 128 MB memory, while the cold task only accesses > its memory briefly andthen call madvise(MADV_FREE). However, khugepaged s/andthen/and then/ > still prioritizes scanning the cold task and only scans the hot2 task > after completing the scan of the cold task. > > And if we collapse with a lazyfree page, that content will never be none > and the deferred shrinker cannot reclaim them. > > So if the user has explicitly informed us via MADV_FREE that this memory > will be freed, it is appropriate for khugepaged to skip it only, thereby > avoiding unnecessary scan and collapse operations to reducing CPU > wastage. > > Here are the performance test results: > (Throughput bigger is better, other smaller is better) > > Testing on x86_64 machine: > > | task hot2 | without patch | with patch | delta | > |---------------------|---------------|---------------|---------| > | total accesses time | 3.14 sec | 2.93 sec | -6.69% | > | cycles per access | 4.96 | 2.21 | -55.44% | > | Throughput | 104.38 M/sec | 111.89 M/sec | +7.19% | > | dTLB-load-misses | 284814532 | 69597236 | -75.56% | > > Testing on qemu-system-x86_64 -enable-kvm: > > | task hot2 | without patch | with patch | delta | > |---------------------|---------------|---------------|---------| > | total accesses time | 3.35 sec | 2.96 sec | -11.64% | > | cycles per access | 7.29 | 2.07 | -71.60% | > | Throughput | 97.67 M/sec | 110.77 M/sec | +13.41% | > | dTLB-load-misses | 241600871 | 3216108 | -98.67% | > > Signed-off-by: Vernon Yang > --- > include/trace/events/huge_memory.h | 1 + > mm/khugepaged.c | 13 +++++++++++++ > 2 files changed, 14 insertions(+) > > diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h > index 384e29f6bef0..bcdc57eea270 100644 > --- a/include/trace/events/huge_memory.h > +++ b/include/trace/events/huge_memory.h > @@ -25,6 +25,7 @@ > EM( SCAN_PAGE_LRU, "page_not_in_lru") \ > EM( SCAN_PAGE_LOCK, "page_locked") \ > EM( SCAN_PAGE_ANON, "page_not_anon") \ > + EM( SCAN_PAGE_LAZYFREE, "page_lazyfree") \ > EM( SCAN_PAGE_COMPOUND, "page_compound") \ > EM( SCAN_ANY_PROCESS, "no_process_for_page") \ > EM( SCAN_VMA_NULL, "vma_null") \ > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index df22b2274d92..b4def001ccd0 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -46,6 +46,7 @@ enum scan_result { > SCAN_PAGE_LRU, > SCAN_PAGE_LOCK, > SCAN_PAGE_ANON, > + SCAN_PAGE_LAZYFREE, > SCAN_PAGE_COMPOUND, > SCAN_ANY_PROCESS, > SCAN_VMA_NULL, > @@ -583,6 +584,12 @@ static enum scan_result __collapse_huge_page_isolate(struct vm_area_struct *vma, > folio = page_folio(page); > VM_BUG_ON_FOLIO(!folio_test_anon(folio), folio); > > + if (cc->is_khugepaged && !pte_dirty(pteval) && > + folio_test_lazyfree(folio)) { > + result = SCAN_PAGE_LAZYFREE; > + goto out; > + } > + > /* See hpage_collapse_scan_pmd(). */ > if (folio_maybe_mapped_shared(folio)) { > ++shared; > @@ -1332,6 +1339,12 @@ static enum scan_result hpage_collapse_scan_pmd(struct mm_struct *mm, > } > folio = page_folio(page); > > + if (cc->is_khugepaged && !pte_dirty(pteval) && > + folio_test_lazyfree(folio)) { > + result = SCAN_PAGE_LAZYFREE; > + goto out_unmap; > + } > + > if (!folio_test_anon(folio)) { > result = SCAN_PAGE_ANON; > goto out_unmap; Nothing else jumped at me, LGTM. Reviewed-by: Lance Yang