From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 061E9C4167D for ; Tue, 14 Nov 2023 12:00:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To: Subject:MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=4a9qNVsZkOzdE5iCgXGprdyamN6DFn0dWl63yPc0u/k=; b=uFjjxXVvSowdnc DYqtltJEMGay/xDTBB/jIOdbwuU3yoUOOenSdrCM9hGqHgRICRtIhPCwAq0Pr70qeTWD5UATP+zGo 9LBYYlX0INGlIPrVpD7gLHgJNZjlOdkPZrCIwqVoNI2IpDmwAtlNqMB6YrIUEnxaiU9lYmnZyTIIU ynKmsSM2OCTOJYa+O0wTnPhIGOYck8rX9ozrmhA64Nb6fk8cbcds4Le10MyzvOBKx4djAZhcVBCuZ lVNNH1bRXwjosgKXj5dPFQqrgTRb7K5lpG++arFD9xpkQ7VL6JhhyrqLbdr03tIU7WJtYVSP4j53z 5jGLQuhHWEXFAFUiTU+w==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1r2s5n-00Frav-2M; Tue, 14 Nov 2023 12:00:31 +0000 Received: from desiato.infradead.org ([2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1r2r6d-00FcpE-2Y for linux-arm-kernel@bombadil.infradead.org; Tue, 14 Nov 2023 10:57:19 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Content-Transfer-Encoding:Content-Type :In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date:Message-ID: Sender:Reply-To:Content-ID:Content-Description; bh=HPWsF2ER4+Rk27FqBwRPqbcWtzHCf7Bh+eSJQ0VKn54=; b=GMEsmrPCSMyJ0K6QaMVaXot3E+ Qdh1a7/V1Lo27tlGalKAdk8vu0sQc1zGRj1m4b+XesHA/+bWjGK4q7batRcouujbgSpVJH210l+NY RJ7Tv2ArTNjAFFlw7DsWBMmqwjPetgz1ZnPC622TQI5IGILoy8EH4A0HzR4i0PxkhjItdD9t1MAtK Sp8VzuXtP/dhJeMM6wl2XMiESYpWtnitsPN5riw93GXJu71gq2RrOBety4TxeJlZf06kTKnAKoGa6 ZHwknGB+9anOCCOOolnR0rgu9eB8xaCQcrqgL6JQQVbiLnU5UMlsbakJu+15j8w7aF2GXaCUqLosH 3a9RcIyA==; Received: from foss.arm.com ([217.140.110.172]) by desiato.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1r2r6Z-002NLM-1n for linux-arm-kernel@lists.infradead.org; Tue, 14 Nov 2023 10:57:18 +0000 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 C9D0CC15; Tue, 14 Nov 2023 02:57:56 -0800 (PST) Received: from [10.1.27.144] (XHFQ2J9959.cambridge.arm.com [10.1.27.144]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1DA963F641; Tue, 14 Nov 2023 02:57:09 -0800 (PST) Message-ID: <181a25c2-219e-4af9-9f8e-e5f514bbc4b6@arm.com> Date: Tue, 14 Nov 2023 10:57:07 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 0/9] variable-order, large folios for anonymous memory Content-Language: en-GB To: Matthew Wilcox Cc: John Hubbard , Andrew Morton , Yin Fengwei , David Hildenbrand , Yu Zhao , Catalin Marinas , Anshuman Khandual , Yang Shi , "Huang, Ying" , Zi Yan , Luis Chamberlain , Itaru Kitayama , "Kirill A. Shutemov" , David Rientjes , Vlastimil Babka , Hugh Dickins , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org References: <20230929114421.3761121-1-ryan.roberts@arm.com> From: Ryan Roberts In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231114_105715_787192_22585946 X-CRM114-Status: GOOD ( 15.99 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 13/11/2023 15:04, Matthew Wilcox wrote: > On Mon, Nov 13, 2023 at 10:19:48AM +0000, Ryan Roberts wrote: >> On 13/11/2023 05:18, Matthew Wilcox wrote: >>> My hope is to abolish the 64kB page size configuration. ie instead of >>> using the mixture of page sizes that you currently are -- 64k and >>> 1M (right? Order-0, and order-4) >> >> Not quite; the contpte-size for a 64K page size is 2M/order-5. (and yes, it is >> 64K/order-4 for a 4K page size, and 2M/order-7 for a 16K page size. I agree that >> intuitively you would expect the order to remain constant, but it doesn't). >> >> The "recommend" setting above will actually enable order-3 as well even though >> there is no HW benefit to this. So the full set of available memory sizes here is: >> >> 64K/order-0, 512K/order-3, 2M/order-5, 512M/order-13 >> >>> , that 4k, 64k and 2MB (order-0, >>> order-4 and order-9) will provide better performance. >>> >>> Have you run any experiements with a 4kB page size? >> >> Agree that would be interesting with 64K small-sized THP enabled. And I'd love >> to get to a world were we universally deal in variable sized chunks of memory, >> aligned on 4K boundaries. >> >> In my experience though, there are still some performance benefits to 64K base >> page vs 4K+contpte; the page tables are more cache efficient for the former case >> - 64K of memory is described by 8 bytes in the former vs 8x16=128 bytes in the >> latter. In practice the HW will still only read 8 bytes in the latter but that's >> taking up a full cache line vs the former where a single cache line stores 8x >> 64K entries. > > This is going to depend on your workload though -- if you're using more > 2MB than 64kB, you get to elide a layer of page table with 4k base, > rather than taking up 4 cache lines with a 64k base. True, but again depending on workload/config, you may have few levels of lookup for the 64K native case in the first place because you consume more VA bits at each level. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel