From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 4C74F1CFA9 for ; Mon, 26 Feb 2024 13:00:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708952461; cv=none; b=C/0M6OrxYsdRgH8PaXp71Hb6O6eerIiV/CoU6tA/ikzQTq8mESfKn+pX2d5l0Y0bx/4yUVO0Q+6dLc2d+ffVx0p2CK5A+CJ+uvJyfyUGVaFSVq7ka/Zp5ZX4zzY6EoqnysJQX+hjuimILuiCvS3TzlQ1a7P2e/KMp9DmJZ2PZ0Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708952461; c=relaxed/simple; bh=gU02AqookQ/IsCX5PRVEZ+njILfZLiVpjGq7vt3Hgjc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ub4WtayR0PumMz7jBY5qjzXO+MtVuSwgXxih80kNU3VRNN+aSnqzAq+/AqFH0gcFGumtfGjyivu8hK6X9duf4sZ/Xou/aToOImXGiM/T6n/5hnbGwtJjWV/Izaxtey3wOWBXDmhMmzsZ4/BM5ICqG/ZngVnEtyKMkp5DFZkVwpk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 2A033DA7; Mon, 26 Feb 2024 05:01:37 -0800 (PST) Received: from [10.57.67.4] (unknown [10.57.67.4]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8574B3F762; Mon, 26 Feb 2024 05:00:56 -0800 (PST) Message-ID: Date: Mon, 26 Feb 2024 13:00:54 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/1] mm/madvise: enhance lazyfreeing with mTHP in madvise_free Content-Language: en-GB To: Lance Yang , akpm@linux-foundation.org Cc: zokeefe@google.com, shy828301@gmail.com, david@redhat.com, mhocko@suse.com, wangkefeng.wang@huawei.com, songmuchun@bytedance.com, peterx@redhat.com, minchan@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20240225123215.86503-1-ioworker0@gmail.com> From: Ryan Roberts In-Reply-To: <20240225123215.86503-1-ioworker0@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Lance, Thanks for working on this! On 25/02/2024 12:32, Lance Yang wrote: > This patch improves madvise_free_pte_range() to correctly > handle large folio that is smaller than PMD-size When you say "correctly handle" are you implying there is a bug with the current implementation or are you just saying you can optimize this to improve performance? I'm not convinced there is a bug, but I agree there is certainly room for performance improvement. Thanks, Ryan > (for example, 16KiB to 1024KiB[1]). It’s probably part of > the preparation to support anonymous multi-size THP. > > Additionally, when the consecutive PTEs are mapped to > consecutive pages of the same large folio (mTHP), if the > folio is locked before madvise(MADV_FREE) or cannot be > split, then all subsequent PTEs within the same PMD will > be skipped. However, they should have been MADV_FREEed. > > Moreover, this patch also optimizes lazyfreeing with > PTE-mapped mTHP (Inspired by David Hildenbrand[2]). We > aim to avoid unnecessary folio splitting if the large > folio is entirely within the given range. > > On an Intel I5 CPU, lazyfreeing a 1GiB VMA backed by > PTE-mapped folios of the same size results in the following > runtimes for madvise(MADV_FREE) in seconds (shorter is better): > > Folio Size | Old | New | Change > ---------------------------------------------- > 4KiB | 0.590251 | 0.590264 | 0% > 16KiB | 2.990447 | 0.182167 | -94% > 32KiB | 2.547831 | 0.101622 | -96% > 64KiB | 2.457796 | 0.049726 | -98% > 128KiB | 2.281034 | 0.030109 | -99% > 256KiB | 2.230387 | 0.015838 | -99% > 512KiB | 2.189106 | 0.009149 | -99% > 1024KiB | 2.183949 | 0.006620 | -99% > 2048KiB | 0.002799 | 0.002795 | 0% > > [1] https://lkml.kernel.org/r/20231207161211.2374093-5-ryan.roberts@arm.com > [2] https://lore.kernel.org/linux-mm/20240214204435.167852-1-david@redhat.com/ > > Signed-off-by: Lance Yang > --- > mm/madvise.c | 69 +++++++++++++++++++++++++++++++++++++++++++--------- > 1 file changed, 58 insertions(+), 11 deletions(-) > > diff --git a/mm/madvise.c b/mm/madvise.c > index cfa5e7288261..bcbf56595a2e 100644 > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -676,11 +676,43 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr, > */ > if (folio_test_large(folio)) { > int err; > + unsigned long next_addr, align; > > - if (folio_estimated_sharers(folio) != 1) > - break; > - if (!folio_trylock(folio)) > - break; > + if (folio_estimated_sharers(folio) != 1 || > + !folio_trylock(folio)) > + goto skip_large_folio; > + > + align = folio_nr_pages(folio) * PAGE_SIZE; > + next_addr = ALIGN_DOWN(addr + align, align); > + > + /* > + * If we mark only the subpages as lazyfree, > + * split the large folio. > + */ > + if (next_addr > end || next_addr - addr != align) > + goto split_large_folio; > + > + /* > + * Avoid unnecessary folio splitting if the large > + * folio is entirely within the given range. > + */ > + folio_test_clear_dirty(folio); > + folio_unlock(folio); > + for (; addr != next_addr; pte++, addr += PAGE_SIZE) { > + ptent = ptep_get(pte); > + if (pte_young(ptent) || pte_dirty(ptent)) { > + ptent = ptep_get_and_clear_full( > + mm, addr, pte, tlb->fullmm); > + ptent = pte_mkold(ptent); > + ptent = pte_mkclean(ptent); > + set_pte_at(mm, addr, pte, ptent); > + tlb_remove_tlb_entry(tlb, pte, addr); > + } > + } > + folio_mark_lazyfree(folio); > + goto next_folio; > + > +split_large_folio: > folio_get(folio); > arch_leave_lazy_mmu_mode(); > pte_unmap_unlock(start_pte, ptl); > @@ -688,13 +720,28 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr, > err = split_folio(folio); > folio_unlock(folio); > folio_put(folio); > - if (err) > - break; > - start_pte = pte = > - pte_offset_map_lock(mm, pmd, addr, &ptl); > - if (!start_pte) > - break; > - arch_enter_lazy_mmu_mode(); > + > + /* > + * If the large folio is locked before madvise(MADV_FREE) > + * or cannot be split, we just skip it. > + */ > + if (err) { > +skip_large_folio: > + if (next_addr >= end) > + break; > + pte += (next_addr - addr) / PAGE_SIZE; > + addr = next_addr; > + } > + > + if (!start_pte) { > + start_pte = pte = pte_offset_map_lock( > + mm, pmd, addr, &ptl); > + if (!start_pte) > + break; > + arch_enter_lazy_mmu_mode(); > + } > + > +next_folio: > pte--; > addr -= PAGE_SIZE; > continue;