From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f72.google.com (mail-pg0-f72.google.com [74.125.83.72]) by kanga.kvack.org (Postfix) with ESMTP id AEEB66B000D for ; Mon, 5 Mar 2018 16:04:12 -0500 (EST) Received: by mail-pg0-f72.google.com with SMTP id v8so7806449pgs.9 for ; Mon, 05 Mar 2018 13:04:12 -0800 (PST) Received: from mga07.intel.com (mga07.intel.com. [134.134.136.100]) by mx.google.com with ESMTPS id d16si8820444pgv.331.2018.03.05.13.04.11 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 05 Mar 2018 13:04:11 -0800 (PST) Subject: Re: [PATCH v12 02/11] mm, swap: Add infrastructure for saving page metadata on swap References: <0d77dc3c-1454-a689-a0fb-f07e8973c29e@linux.intel.com> <4a766f6d-ba96-7963-b367-7214eab7e307@oracle.com> <66c8ab93-f491-ad2e-5313-d03e23f73006@oracle.com> From: Dave Hansen Message-ID: <0709b55b-3b77-ba43-efbc-6f767714a0b7@linux.intel.com> Date: Mon, 5 Mar 2018 13:04:10 -0800 MIME-Version: 1.0 In-Reply-To: <66c8ab93-f491-ad2e-5313-d03e23f73006@oracle.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Khalid Aziz , akpm@linux-foundation.org, davem@davemloft.net, arnd@arndb.de Cc: kirill.shutemov@linux.intel.com, mhocko@suse.com, ross.zwisler@linux.intel.com, dave.jiang@intel.com, mgorman@techsingularity.net, willy@infradead.org, hughd@google.com, minchan@kernel.org, hannes@cmpxchg.org, shli@fb.com, mingo@kernel.org, jglisse@redhat.com, me@tobin.cc, anthony.yznaga@oracle.com, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, sparclinux@vger.kernel.org, Khalid Aziz On 03/05/2018 12:28 PM, Khalid Aziz wrote: >> Do you have a way to tell that data is not being thrown away?A Like if >> the ADI metadata is different for two different cachelines within a >> single page? > > Yes, since access to tagged data is made using pointers with ADI tag > embedded in the top bits, any mismatch between what app thinks the ADI > tags should be and what is stored in the RAM for corresponding page will > result in exception. If ADI data gets thrown away, we will get an ADI > tag mismatch exception. If ADI tags for two different ADI blocks on a > page are different when app expected them to be the same, we will see an > exception on access to the block with wrong ADI data. So, when an app has two different ADI tags on two parts of a page, the page gets swapped, and the ADI block size is under PAGE_SIZE, the app will get an ADI exception after swap-in through no fault of its own? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org