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Mon, 26 Feb 2024 00:35:41 -0800 (PST) Received: from LancedeMBP.lan ([112.10.225.117]) by smtp.gmail.com with ESMTPSA id h14-20020a63df4e000000b005dc4806ad7dsm3508416pgj.40.2024.02.26.00.35.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Feb 2024 00:35:41 -0800 (PST) From: Lance Yang To: fengwei.yin@intel.com Cc: akpm@linux-foundation.org, david@redhat.com, ioworker0@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.com, minchan@kernel.org, peterx@redhat.com, ryan.roberts@arm.com, shy828301@gmail.com, songmuchun@bytedance.com, wangkefeng.wang@huawei.com, zokeefe@google.com, 21cnbao@gmail.com Subject: Re: [PATCH 1/1] mm/madvise: enhance lazyfreeing with mTHP in madvise_free Date: Mon, 26 Feb 2024 16:35:26 +0800 Message-Id: <20240226083526.26002-1-ioworker0@gmail.com> X-Mailer: git-send-email 2.33.1 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 949521A0014 X-Stat-Signature: y7si3uktb5w7cb4dj14daw5633cxwniz X-HE-Tag: 1708936542-121425 X-HE-Meta: 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 eAPGmnv0 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000017, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hey Fengwei, Thanks for taking time to review! > On Mon, Feb 26, 2024 at 10:38 AM Yin Fengwei wrote: > > On Sun, Feb 25, 2024 at 8:32 PM Lance Yang wrote: [...] > > --- 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); > There is a possible corner case: > If there is a cow folio associated with this folio and the cow folio > has smaller size than this folio for whatever reason, this change can't > handle it correctly. Thanks for pointing that out; it's very helpful to me! I made some changes. Could you please check if this corner case is now resolved? As a diff against this patch. diff --git a/mm/madvise.c b/mm/madvise.c index bcbf56595a2e..c7aacc9f9536 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -686,10 +686,12 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr, next_addr = ALIGN_DOWN(addr + align, align); /* - * If we mark only the subpages as lazyfree, - * split the large folio. + * If we mark only the subpages as lazyfree, or + * if there is a cow folio associated with this folio, + * then split the large folio. */ - if (next_addr > end || next_addr - addr != align) + if (next_addr > end || next_addr - addr != align || + folio_total_mapcount(folio) != folio_nr_pages(folio)) goto split_large_folio; /* --- Thanks again for your time! Best, Lance