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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 41659CF6BE3 for ; Wed, 7 Jan 2026 01:46:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Reply-To:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To: Content-Transfer-Encoding:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=IeLz8B+FFA+xmUGLHkiMAf9w6+beNxbYkBoeeKfR+nQ=; b=yYzRmQvHHfT29lu4yUcKP9iH9g Ua3PPB2h5RL+qVaVgklULdTMLfvZkYJM1vwkUXSRlNSVYK5YZ2guRzFVVlShk8Yh4geAcRtptWr4T eH99sXU5vHvKYgablDwcUkESgqcgfx497zadrNOUQcUg8+b3G7gE2xjx4Ug/xm8twhVnsVrFmO7gf dMGtzGhmPeetionrqZDc6PtawPB8cKf4EK4PSAkH+GhwCtDIZiQkTbisOMFoVcOCKGEXIjFOqFGHH NsqPNE7Ly/1fQYTkbHnqLQO2UpYkhAfMIlfHvW9IuUZYC7FfzOi4cy+miKQ/D1yMTk7ZCXC9xE3KE 1/mTTN9g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vdIch-0000000E1Wv-1n2j; Wed, 07 Jan 2026 01:46:07 +0000 Received: from mail-ej1-x643.google.com ([2a00:1450:4864:20::643]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vdIce-0000000E1WY-3hFy for linux-arm-kernel@lists.infradead.org; Wed, 07 Jan 2026 01:46:06 +0000 Received: by mail-ej1-x643.google.com with SMTP id a640c23a62f3a-b7cf4a975d2so267268366b.2 for ; Tue, 06 Jan 2026 17:46:04 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1767750363; x=1768355163; darn=lists.infradead.org; h=user-agent:in-reply-to:content-transfer-encoding :content-disposition:mime-version:references:reply-to:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=IeLz8B+FFA+xmUGLHkiMAf9w6+beNxbYkBoeeKfR+nQ=; b=Iqc+GJ604uerg93RGRoKuKW8HvrulnvLaSt/ps8EP+MImsXokewUQ5k9UX6G2qhOB1 F5MaRLT9Wdwpia1ChtrYHzOBznHrCPE6aSJiJax0bqglfo+Ie4+UCzrvZ5yYNEM85WRJ 1Ev97SeZDygbIppfooLwzHxuglPeHk862F2s0WI0p2+kd1z5M75C8Xf3C4TQnE0yBu4x B8nZF09ZKjMpbGmqw4iszlrqG64S+zVguTzE5bxMprzzO0MFGZTfdALqnoqO/v29F+NT OxOHKx6c0rW9VqsaA6gEjbCoFXIawbjCMCRBzBljmCA76o+AFt/dbG1hZPvFaSzgt/ld B3YA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1767750363; x=1768355163; h=user-agent:in-reply-to:content-transfer-encoding :content-disposition:mime-version:references:reply-to:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=IeLz8B+FFA+xmUGLHkiMAf9w6+beNxbYkBoeeKfR+nQ=; b=such0SRb1xHTVR9vaHwk06S6iv2eWYXjbSGyMEDevn2QjWjveo6t4TU4EP00PQLUnp VV3LjJou5OKBXQeQ06BFQEKqsPVE8H4Ti/VTmrMDQzGRQPVtKQzBm0khX8st1Add+6to BfpaOgiEvrxp5P5LAepvw0v2CuiaVF6q1jGcSjz3N/rdJTPtv96gfanOncWN72n+0Q38 1HdHlyNpTH5cvlJK75jzW/Q0kJd+PJhKsHtKJf3QB9qVXuPA78yBsb8Ccso0zfRmfRZX eCdY58L35K0Hqyjdv760G47rcNh7Yjky46HfvkFuYTTRBisemcvsjfxC/4p6kcEg2DjE a4TQ== X-Forwarded-Encrypted: i=1; AJvYcCW9Hol5C0ZQ5XDNuzRScbfHwOIFE2fWWXoKYdV1rw6m9GTw9DZMcJOALi4nfv9imzejm0/xju3GA2ca0PCPOZOF@lists.infradead.org X-Gm-Message-State: AOJu0YzJdzWv+OXPg1A8tWVqIE7AK5+K0N0Xbk/Jf1InQrSkTr/r252e ovlY7g+6rzG5cOWFsQ7flGxXJw/U4QJ62kuX7HgwdEto5TvBiHxVg8Ck X-Gm-Gg: AY/fxX4jFnfyV9fYaci6NdYQwd6nqqilCi7EyR4JvdBm/YEzMbn05+62ykxjmEfP2y5 pW2K3klbXrNe1UEhraJ9uhka0zEus8/dJwS6H7NVSNHNI4hNlhV8cJmKWKMIDAi8/my4nEF/YYg tIBnMnevEdegJlVPz8d9A2Nonh0AfrF+IczfDgx9GxGtOFhkrqGVywrGkBADzlvlIZB/sgBpiMV kMTBb3nOvGA3nmyoS1FF9ZCsBDwNblqBaKVawK5Yv9ORnYQtnlvrsldqRGax1LxqO7QMX/DFzak 3cAYtWQnH1QGVR7FWJPh5Uddhbok2YL5fr9giGNRme7w7LoTioaDfPpOxRqr1zonvaRL+TH8JY2 koZhAEGiFfc0wkURvcDO2MFpQgFks/HLbN5UwGTNp+/7CPx7BrDnMfFE4ag13Lww3nDcle7Ifk0 BL/j+R/zZK6csD9qXDqKB5 X-Google-Smtp-Source: AGHT+IFeA6mkv79CriXKt6qQAcQGV8CynmdXfqBxQvsbb+Aj2IP7Z2BA07re20HuxUP8m4dAAyg8xw== X-Received: by 2002:a17:906:ef02:b0:b80:751:ee62 with SMTP id a640c23a62f3a-b8444c8e95bmr98318966b.14.1767750362536; Tue, 06 Jan 2026 17:46:02 -0800 (PST) Received: from localhost ([185.92.221.13]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b842a230db0sm375951066b.2.2026.01.06.17.46.01 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Tue, 06 Jan 2026 17:46:02 -0800 (PST) Date: Wed, 7 Jan 2026 01:46:01 +0000 From: Wei Yang To: Barry Song <21cnbao@gmail.com> Cc: Wei Yang , Baolin Wang , akpm@linux-foundation.org, david@kernel.org, catalin.marinas@arm.com, will@kernel.org, lorenzo.stoakes@oracle.com, ryan.roberts@arm.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, riel@surriel.com, harry.yoo@oracle.com, jannh@google.com, willy@infradead.org, dev.jain@arm.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 5/5] mm: rmap: support batched unmapping for file large folios Message-ID: <20260107014601.dxvq6b7ljgxwg7iu@master> References: <142919ac14d3cf70cba370808d85debe089df7b4.1766631066.git.baolin.wang@linux.alibaba.com> <20260106132203.kdxfvootlkxzex2l@master> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: NeoMutt/20170113 (1.7.2) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260106_174605_070579_EE8F0867 X-CRM114-Status: GOOD ( 27.41 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Wei Yang Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Jan 07, 2026 at 10:29:25AM +1300, Barry Song wrote: >On Wed, Jan 7, 2026 at 2:22 AM Wei Yang wrote: >> >> On Fri, Dec 26, 2025 at 02:07:59PM +0800, Baolin Wang wrote: >> >Similar to folio_referenced_one(), we can apply batched unmapping for file >> >large folios to optimize the performance of file folios reclamation. >> > >> >Barry previously implemented batched unmapping for lazyfree anonymous large >> >folios[1] and did not further optimize anonymous large folios or file-backed >> >large folios at that stage. As for file-backed large folios, the batched >> >unmapping support is relatively straightforward, as we only need to clear >> >the consecutive (present) PTE entries for file-backed large folios. >> > >> >Performance testing: >> >Allocate 10G clean file-backed folios by mmap() in a memory cgroup, and try to >> >reclaim 8G file-backed folios via the memory.reclaim interface. I can observe >> >75% performance improvement on my Arm64 32-core server (and 50%+ improvement >> >on my X86 machine) with this patch. >> > >> >W/o patch: >> >real 0m1.018s >> >user 0m0.000s >> >sys 0m1.018s >> > >> >W/ patch: >> >real 0m0.249s >> >user 0m0.000s >> >sys 0m0.249s >> > >> >[1] https://lore.kernel.org/all/20250214093015.51024-4-21cnbao@gmail.com/T/#u >> >Reviewed-by: Ryan Roberts >> >Acked-by: Barry Song >> >Signed-off-by: Baolin Wang >> >--- >> > mm/rmap.c | 7 ++++--- >> > 1 file changed, 4 insertions(+), 3 deletions(-) >> > >> >diff --git a/mm/rmap.c b/mm/rmap.c >> >index 985ab0b085ba..e1d16003c514 100644 >> >--- a/mm/rmap.c >> >+++ b/mm/rmap.c >> >@@ -1863,9 +1863,10 @@ static inline unsigned int folio_unmap_pte_batch(struct folio *folio, >> > end_addr = pmd_addr_end(addr, vma->vm_end); >> > max_nr = (end_addr - addr) >> PAGE_SHIFT; >> > >> >- /* We only support lazyfree batching for now ... */ >> >- if (!folio_test_anon(folio) || folio_test_swapbacked(folio)) >> >+ /* We only support lazyfree or file folios batching for now ... */ >> >+ if (folio_test_anon(folio) && folio_test_swapbacked(folio)) >> > return 1; >> >+ >> > if (pte_unused(pte)) >> > return 1; >> > >> >@@ -2231,7 +2232,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, >> > * >> > * See Documentation/mm/mmu_notifier.rst >> > */ >> >- dec_mm_counter(mm, mm_counter_file(folio)); >> >+ add_mm_counter(mm, mm_counter_file(folio), -nr_pages); >> > } >> > discard: >> > if (unlikely(folio_test_hugetlb(folio))) { >> >-- >> >2.47.3 >> > >> >> Hi, Baolin >> >> When reading your patch, I come up one small question. >> >> Current try_to_unmap_one() has following structure: >> >> try_to_unmap_one() >> while (page_vma_mapped_walk(&pvmw)) { >> nr_pages = folio_unmap_pte_batch() >> >> if (nr_pages = folio_nr_pages(folio)) >> goto walk_done; >> } >> >> I am thinking what if nr_pages > 1 but nr_pages != folio_nr_pages(). >> >> If my understanding is correct, page_vma_mapped_walk() would start from >> (pvmw->address + PAGE_SIZE) in next iteration, but we have already cleared to >> (pvmw->address + nr_pages * PAGE_SIZE), right? >> >> Not sure my understanding is correct, if so do we have some reason not to >> skip the cleared range? > >I don’t quite understand your question. For nr_pages > 1 but not equal >to nr_pages, page_vma_mapped_walk will skip the nr_pages - 1 PTEs inside. > >take a look: > >next_pte: > do { > pvmw->address += PAGE_SIZE; > if (pvmw->address >= end) > return not_found(pvmw); > /* Did we cross page table boundary? */ > if ((pvmw->address & (PMD_SIZE - PAGE_SIZE)) == 0) { > if (pvmw->ptl) { > spin_unlock(pvmw->ptl); > pvmw->ptl = NULL; > } > pte_unmap(pvmw->pte); > pvmw->pte = NULL; > pvmw->flags |= PVMW_PGTABLE_CROSSED; > goto restart; > } > pvmw->pte++; > } while (pte_none(ptep_get(pvmw->pte))); > Yes, we do it in page_vma_mapped_walk() now. Since they are pte_none(), they will be skipped. I mean maybe we can skip it in try_to_unmap_one(), for example: diff --git a/mm/rmap.c b/mm/rmap.c index 9e5bd4834481..ea1afec7c802 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -2250,6 +2250,10 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, */ if (nr_pages == folio_nr_pages(folio)) goto walk_done; + else { + pvmw.address += PAGE_SIZE * (nr_pages - 1); + pvmw.pte += nr_pages - 1; + } continue; walk_abort: ret = false; Not sure this is reasonable. -- Wei Yang Help you, Help me