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 4F84330F938 for ; Tue, 23 Jun 2026 10:05:28 +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=1782209130; cv=none; b=cJIurlcLVBRvg5X9Tq9UKgkk5DXrJERAEcRI/FsHuVEacqEAYOPMfQDgDIDUarcXOlPHS1Qz1ZeTuCVM7M0bZI701lfAbIX3j92g3xwQuCrHqbvRA1rUHkHnSjse2g4zxTwzpM3xp/zGTsfXJrUWQs7g08vj0Vz9dELoTyhmfz8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782209130; c=relaxed/simple; bh=iCAi4kghzK4zKgQDV+QmVx1z4g6L/JSiiDzsaIfIioA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=OtujQMkHsJczfddMpl+olIKNIWOGL6Jh37KvzPps8uTDrWNL8fuRiOl1mqJfm7mJtHnA8zmwie6R5ad5umJiTPBDDfVrNvvB4ySpe4mG/QrRABKazWpX7pA52Zqva8KH6Y/egqW5QLgYBTcoXcPnd7gdES+iU8sQZQWmzi4X3GY= 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; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=iXq0M+bk; 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 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="iXq0M+bk" 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 85E0A1A25; Tue, 23 Jun 2026 03:05:22 -0700 (PDT) Received: from [10.164.19.14] (unknown [10.164.19.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id AFEAA3F632; Tue, 23 Jun 2026 03:05:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1782209127; bh=iCAi4kghzK4zKgQDV+QmVx1z4g6L/JSiiDzsaIfIioA=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=iXq0M+bkRbXaLZQCmiCkj8WpNZ/Usqvwrkt6+n/60955gaN/J4rHZ0YTEueZa2S0b 01YBisTnjFIJm7PScsGEomxLX4Qgk7odBt/1E9Q809URtPSf8oTt8gVaPCKGw093BZ W6+vDV1IdhKpFm6hx25sUQxsoSYjOKbXOkUfcsxc= Message-ID: Date: Tue, 23 Jun 2026 15:35:16 +0530 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 v4 09/12] mm/rmap: Add batched version of folio_try_share_anon_rmap_pte To: "David Hildenbrand (Arm)" , akpm@linux-foundation.org, ljs@kernel.org, chrisl@kernel.org, kasong@tencent.com, hughd@google.com, liam@infradead.org Cc: riel@surriel.com, vbabka@kernel.org, harry@kernel.org, jannh@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, qi.zheng@linux.dev, shakeel.butt@linux.dev, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, bhe@redhat.com, youngjun.park@lge.com, baolin.wang@linux.alibaba.com, pfalcato@suse.de, ryan.roberts@arm.com, anshuman.khandual@arm.com References: <20260526063635.61721-1-dev.jain@arm.com> <20260526063635.61721-10-dev.jain@arm.com> <2a1781f3-741b-4073-b23f-f5cb3f0d98e2@kernel.org> Content-Language: en-US From: Dev Jain In-Reply-To: <2a1781f3-741b-4073-b23f-f5cb3f0d98e2@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 16/06/26 7:34 pm, David Hildenbrand (Arm) wrote: > On 5/26/26 08:36, Dev Jain wrote: >> To enable batched unmapping of anonymous folios, we need to handle the >> sharing of exclusive pages. Hence, a batched version of >> folio_try_share_anon_rmap_pte is required. >> >> Currently, the sole purpose of nr_pages in __folio_try_share_anon_rmap is >> to do some rmap sanity checks. Now, clear the PageAnonExclusive bit on a >> batch of nr_pages. Refactor the function such that the clearing of the bit >> can be done at one place without duplication. >> >> Note that __folio_try_share_anon_rmap can receive nr_pages == HPAGE_PMD_NR >> from the PMD path, but currently we only clear the bit on the head page. >> Retain this behaviour by setting nr_pages = 1 in case the caller is >> folio_try_share_anon_rmap_pmd. >> >> While at it, convert nr_pages to unsigned long to future-proof from >> overflow in case P4D-huge mappings etc get supported down the road. >> I haven't made such a change in each function receiving nr_pages in >> try_to_unmap_one - perhaps this can be done incrementally. >> >> Signed-off-by: Dev Jain >> --- >> include/linux/rmap.h | 52 +++++++++++++++++++++++++++++--------------- >> 1 file changed, 35 insertions(+), 17 deletions(-) >> >> diff --git a/include/linux/rmap.h b/include/linux/rmap.h >> index 8dc0871e5f001..64929490a7cfc 100644 >> --- a/include/linux/rmap.h >> +++ b/include/linux/rmap.h >> @@ -706,17 +706,18 @@ static inline int folio_try_dup_anon_rmap_pmd(struct folio *folio, >> } >> >> static __always_inline int __folio_try_share_anon_rmap(struct folio *folio, >> - struct page *page, int nr_pages, enum pgtable_level level) >> + struct page *page, unsigned long nr_pages, enum pgtable_level level) >> { >> + /* device private folios cannot get pinned via GUP. */ >> + const bool pinnable = likely(!folio_is_device_private(folio)); > > We don't seem to have a lot of users of likely/unlikely when assigning > variables, so I wonder if the compiler really uses that information then. > > git grep " = " | grep "likely(" | grep ";$" | wc -l > 32 > > > Maybe clearer to just push the "likely" into the actual two condition below. Ok. > > [...] > >> /** >> - * folio_try_share_anon_rmap_pte - try marking an exclusive anonymous page >> - * mapped by a PTE possibly shared to prepare >> + * folio_try_share_anon_rmap_ptes - try marking exclusive anonymous pages >> + * mapped by PTEs possibly shared to prepare >> * for KSM or temporary unmapping >> * @folio: The folio to share a mapping of >> - * @page: The mapped exclusive page >> + * @page: The first mapped exclusive page of the batch in the folio >> + * @nr_pages: The number of pages to share in the folio (batch size) >> * >> * The caller needs to hold the page table lock and has to have the page table >> * entries cleared/invalidated. >> @@ -797,11 +807,19 @@ static __always_inline int __folio_try_share_anon_rmap(struct folio *folio, >> * >> * Returns 0 if marking the mapped page possibly shared succeeded. Returns >> * -EBUSY otherwise. >> + * >> + * The caller needs to hold the page table lock. > > Isn't that stated further above? I'll drop it. > >> */ >> +static inline int folio_try_share_anon_rmap_ptes(struct folio *folio, >> + struct page *page, unsigned long nr_pages) >> +{ >> + return __folio_try_share_anon_rmap(folio, page, nr_pages, PGTABLE_LEVEL_PTE); >> +} >> + >> static inline int folio_try_share_anon_rmap_pte(struct folio *folio, >> struct page *page) >> { >> - return __folio_try_share_anon_rmap(folio, page, 1, PGTABLE_LEVEL_PTE); >> + return folio_try_share_anon_rmap_ptes(folio, page, 1); >> } >> >> /** > > In general, LGTM. >