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 5216E7E1 for ; Tue, 7 May 2024 12:36:49 +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=1715085411; cv=none; b=KBvFcjFKd7EwXOaLp553KQlbQ/iH2g0GP79aFNHB0xq6vbgkzFBqDOd67zzGOdsWudkuDPrP5bxr9wmVY0I15qaDKRcjNN9QdNehsLY2QOBJsl9wOFhwUlrbAKCceHZ8hUlZD8qo98P3RSN3xOUgxLW5gxV3DlPVnZkAh/D8S9o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715085411; c=relaxed/simple; bh=NUFfVBcD6D0ZGUtr0OgcfTxuwVwuy013FrR3Yaj6sN0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=rbxzBEwLLGmvW8sw13iSt+rDufug/Agf8sQ3/92fo5ZSYzSbEKeKlV/e58bOs/JfzQfJESLwKzyNr0IS7CgsYP2r4D2NcjiZuoIYpGw000EIycogLMRTVJusjWxfI3d7GNPfe4hFnyTKH1pjVWr1ZA8BuLQMC/IMafJJacIFiq0= 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 895B01063; Tue, 7 May 2024 05:37:14 -0700 (PDT) Received: from [10.1.34.181] (XHFQ2J9959.cambridge.arm.com [10.1.34.181]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 37A2E3F793; Tue, 7 May 2024 05:36:47 -0700 (PDT) Message-ID: <08de71f6-f049-4c3b-977e-f658f85cd734@arm.com> Date: Tue, 7 May 2024 13:36:45 +0100 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: [RESEND PATCH] mm: align larger anonymous mappings on THP boundaries Content-Language: en-GB To: David Hildenbrand , Kefeng Wang , Yang Shi Cc: Matthew Wilcox , Yang Shi , riel@surriel.com, cl@linux.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Ze Zuo References: <20231214223423.1133074-1-yang@os.amperecomputing.com> <1e8f5ac7-54ce-433a-ae53-81522b2320e1@arm.com> <1dc9a561-55f7-4d65-8b86-8a40fa0e84f9@arm.com> <6016c0e9-b567-4205-8368-1f1c76184a28@huawei.com> <2c14d9ad-c5a3-4f29-a6eb-633cdf3a5e9e@redhat.com> <4e7ce57f-cad1-44d5-a1d8-4cd47683a358@arm.com> <9ce8a0f4-d1af-44ea-87b5-57ebdb3d2910@arm.com> From: Ryan Roberts In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 07/05/2024 12:42, David Hildenbrand wrote: > On 07.05.24 13:34, David Hildenbrand wrote: >> On 07.05.24 13:26, Ryan Roberts wrote: >>> On 07/05/2024 12:14, Ryan Roberts wrote: >>>> On 07/05/2024 12:13, David Hildenbrand wrote: >>>>> >>>>>> https://github.com/intel/lmbench/blob/master/src/lat_mem_rd.c#L95 >>>>>> >>>>>>> suggest. If you want to try something semi-randomly; it might be useful >>>>>>> to rule >>>>>>> out the arm64 contpte feature. I don't see how that would be interacting >>>>>>> here if >>>>>>> mTHP is disabled (is it?). But its new for 6.9 and arm64 only. Disable with >>>>>>> ARM64_CONTPTE (needs EXPERT) at compile time. >>>>>> I don't enabled mTHP, so it should be not related about ARM64_CONTPTE, >>>>>> but will have a try. >>>>> >>>>> cont-pte can get active if we're just lucky when allocating pages in the right >>>>> order, correct Ryan? >>>> >>>> No it shouldn't do; it requires the pages to be in the same folio. >> >> Ah, my memory comes back. That's also important for folio_pte_batch() to >> currently work as expected I think. We could change that, though, and >> let cont-pte batch across folios. > > Thinking about it (and trying to refresh my memories), access/dirty bits might > be why we don't want to do that. Yes correct; we only get a single access/dirty bit for the whole contpte block. So can't honour the core kernel's tracking requirements when the pages are not part of a single folio.