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a="161966644" X-IronPort-AV: E=Sophos;i="5.77,323,1596524400"; d="scan'208";a="161966644" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Oct 2020 06:49:38 -0700 IronPort-SDR: cHB0WEBqqp5eBTGgPzubMfNdMfAt8k2/QNp6m4asfXZQ/yz5fES3NImI90HEj2fmDGwbgOc1a8 6QUXhkkc1M8g== X-IronPort-AV: E=Sophos;i="5.77,323,1596524400"; d="scan'208";a="308636996" Received: from kignaci-mobl1.amr.corp.intel.com (HELO [10.251.133.95]) ([10.251.133.95]) by orsmga003-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Oct 2020 06:49:36 -0700 Subject: Re: [PATCH V8 1/4] perf/core: Add PERF_SAMPLE_DATA_PAGE_SIZE To: Peter Zijlstra Cc: "Liang, Kan" , Stephane Eranian , Ingo Molnar , Arnaldo Carvalho de Melo , LKML , Mark Rutland , Alexander Shishkin , Jiri Olsa , Andi Kleen , kirill.shutemov@linux.intel.com, Michael Ellerman , benh@kernel.crashing.org, Paul Mackerras References: <20200921152653.3924-1-kan.liang@linux.intel.com> <20200921152653.3924-2-kan.liang@linux.intel.com> <4e974520-6d0f-68af-7eb8-fa52d95ba77b@linux.intel.com> <35e875ba-2c04-8452-5105-ccacf72840d8@intel.com> <20200930173042.GD2628@hirez.programming.kicks-ass.net> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200930173042.GD2628@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/30/20 10:30 AM, Peter Zijlstra wrote: > In general though; I think using ->active_mm is a mistake though. That > code should be doing something like: > > > mm = current->mm; > if (!mm) > mm = &init_mm; > I was hoping that using ->active_mm would give us the *actual* copy of the page tables that's loaded in CR3 for kernel thraeds. But, there are few if any practical advantages of doing that at the moment. Using that ^ is fine with me.