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[2003:cb:c724:4300:430f:1c83:1abc:1d66]) by smtp.gmail.com with ESMTPSA id z17-20020a05600c0a1100b00416b8da335esm2010126wmp.48.2024.04.11.04.20.11 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 11 Apr 2024 04:20:12 -0700 (PDT) Message-ID: <013334d5-62d2-4256-8045-168893a0a0cf@redhat.com> Date: Thu, 11 Apr 2024 13:20:11 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 1/2] mm/madvise: optimize lazyfreeing with mTHP in madvise_free To: Ryan Roberts , Lance Yang , akpm@linux-foundation.org Cc: 21cnbao@gmail.com, mhocko@suse.com, fengwei.yin@intel.com, zokeefe@google.com, shy828301@gmail.com, xiehuan09@gmail.com, wangkefeng.wang@huawei.com, songmuchun@bytedance.com, peterx@redhat.com, minchan@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20240408042437.10951-1-ioworker0@gmail.com> <20240408042437.10951-2-ioworker0@gmail.com> <38c4add8-53a2-49ca-9f1b-f62c2ee3e764@arm.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 07873C0015 X-Stat-Signature: kscuc41r4mimf8n8wu68tjr1n7qwxtdk X-HE-Tag: 1712834416-821868 X-HE-Meta: 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 x7edH4Jp 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 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 11.04.24 13:11, Ryan Roberts wrote: > On 08/04/2024 05:24, Lance Yang wrote: >> This patch optimizes lazyfreeing with PTE-mapped mTHP[1] >> (Inspired by David Hildenbrand[2]). We aim to avoid unnecessary folio >> splitting if the large folio is fully mapped within the target range. >> >> If a large folio is locked or shared, or if we fail to split it, we just >> leave it in place and advance to the next PTE in the range. But note that >> the behavior is changed; previously, any failure of this sort would cause >> the entire operation to give up. As large folios become more common, >> sticking to the old way could result in wasted opportunities. >> >> 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 | 0.590259 | 0% >> 16KiB | 2.990447 | 0.185655 | -94% >> 32KiB | 2.547831 | 0.104870 | -95% >> 64KiB | 2.457796 | 0.052812 | -97% >> 128KiB | 2.281034 | 0.032777 | -99% >> 256KiB | 2.230387 | 0.017496 | -99% >> 512KiB | 2.189106 | 0.010781 | -99% >> 1024KiB | 2.183949 | 0.007753 | -99% >> 2048KiB | 0.002799 | 0.002804 | 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 >> --- >> include/linux/pgtable.h | 34 +++++++++ >> mm/internal.h | 12 +++- >> mm/madvise.c | 149 ++++++++++++++++++++++------------------ >> mm/memory.c | 4 +- >> 4 files changed, 129 insertions(+), 70 deletions(-) >> >> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h >> index 0f4b2faa1d71..4dd442787420 100644 >> --- a/include/linux/pgtable.h >> +++ b/include/linux/pgtable.h >> @@ -489,6 +489,40 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm, >> } >> #endif >> >> +#ifndef mkold_clean_ptes >> +/** >> + * mkold_clean_ptes - Mark PTEs that map consecutive pages of the same folio >> + * as old and clean. >> + * @mm: Address space the pages are mapped into. >> + * @addr: Address the first page is mapped at. >> + * @ptep: Page table pointer for the first entry. >> + * @nr: Number of entries to mark old and clean. >> + * >> + * May be overridden by the architecture; otherwise, implemented by >> + * get_and_clear/modify/set for each pte in the range. >> + * >> + * Note that PTE bits in the PTE range besides the PFN can differ. For example, >> + * some PTEs might be write-protected. >> + * >> + * Context: The caller holds the page table lock. The PTEs map consecutive >> + * pages that belong to the same folio. The PTEs are all in the same PMD. >> + */ >> +static inline void mkold_clean_ptes(struct mm_struct *mm, unsigned long addr, >> + pte_t *ptep, unsigned int nr) > > Just thinking out loud, I wonder if it would be cleaner to convert mkold_ptes() > (which I added as part of swap-out) to something like: > > clear_young_dirty_ptes(struct mm_struct *mm, unsigned long addr, > pte_t *ptep, unsigned int nr, > bool clear_young, bool clear_dirty); > > Then we can use the same function for both use cases and also have the ability > to only clear dirty in future if we ever need it. The other advantage is that we > only need to plumb a single function down the arm64 arch code. As it currently > stands, those 2 functions would be duplicating most of their code. Yes. Maybe better use proper __bitwise flags, the compiler should be smart enough to optimize either way. -- Cheers, David / dhildenb