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imf21.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf21.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1712917270; a=rsa-sha256; cv=none; b=lVKWDaMD15TrfcuyMhyombQn/dkvl7O3k4ajSHFDgHrogkDl7RszuIxjzFE9g3VERucChk bjLQzcYdCIq5cCE7pwXEnkmtb1xj4i6otFbVSJsOCNEcGX85uqL8bljE/fBztcpC27YTdd 7ipgX/pZztomOWOPC87odYC2qwULtVs= 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 697C4339; Fri, 12 Apr 2024 03:21:39 -0700 (PDT) Received: from [10.57.73.208] (unknown [10.57.73.208]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 173113F64C; Fri, 12 Apr 2024 03:21:07 -0700 (PDT) Message-ID: <2eae1247-02dc-47e1-b9b2-317a73937651@arm.com> Date: Fri, 12 Apr 2024 11:21:06 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 4/4] mm: correct the docs for thp_fault_alloc and thp_fault_fallback Content-Language: en-GB To: Barry Song <21cnbao@gmail.com>, akpm@linux-foundation.org, linux-mm@kvack.org Cc: cerasuolodomenico@gmail.com, chrisl@kernel.org, david@redhat.com, kasong@tencent.com, linux-kernel@vger.kernel.org, peterx@redhat.com, surenb@google.com, v-songbaohua@oppo.com, willy@infradead.org, yosryahmed@google.com, yuzhao@google.com, corbet@lwn.net References: <20240412073740.294272-1-21cnbao@gmail.com> <20240412073740.294272-5-21cnbao@gmail.com> From: Ryan Roberts In-Reply-To: <20240412073740.294272-5-21cnbao@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: D0AD91C000C X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: uqsy1czmzyrkozh4opja54rmxzj4tx4c X-HE-Tag: 1712917270-575325 X-HE-Meta: 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 +pWyHezE 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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 12/04/2024 08:37, Barry Song wrote: > From: Barry Song > > The documentation does not align with the code. In > __do_huge_pmd_anonymous_page(), THP_FAULT_FALLBACK is incremented when > mem_cgroup_charge() fails, despite the allocation succeeding, whereas > THP_FAULT_ALLOC is only incremented after a successful charge. > > Signed-off-by: Barry Song > Cc: Chris Li > Cc: David Hildenbrand > Cc: Domenico Cerasuolo > Cc: Kairui Song > Cc: Matthew Wilcox (Oracle) > Cc: Peter Xu > Cc: Ryan Roberts > Cc: Suren Baghdasaryan > Cc: Yosry Ahmed > Cc: Yu Zhao > Cc: Jonathan Corbet Reviewed-by: Ryan Roberts > --- > Documentation/admin-guide/mm/transhuge.rst | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst > index f436ff982f22..98e3a99ea780 100644 > --- a/Documentation/admin-guide/mm/transhuge.rst > +++ b/Documentation/admin-guide/mm/transhuge.rst > @@ -369,7 +369,7 @@ monitor how successfully the system is providing huge pages for use. > > thp_fault_alloc > is incremented every time a huge page is successfully > - allocated to handle a page fault. > + allocated and charged to handle a page fault. > > thp_collapse_alloc > is incremented by khugepaged when it has found > @@ -377,7 +377,7 @@ thp_collapse_alloc > successfully allocated a new huge page to store the data. > > thp_fault_fallback > - is incremented if a page fault fails to allocate > + is incremented if a page fault fails to allocate or charge > a huge page and instead falls back to using small pages. > > thp_fault_fallback_charge