Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH] mm: Add new vma flag VM_LOCAL_CPU
To:     Peter Zijlstra <peterz@infradead.org>,
        Boaz Harrosh <boazh@netapp.com>
References: <0efb5547-9250-6b6c-fe8e-cf4f44aaa5eb@netapp.com>
 <20180514144901.0fe99d240ff8a53047dd512e@linux-foundation.org>
 <20180515004406.GB5168@bombadil.infradead.org>
 <cff721c3-65e8-c1e8-9f6d-c37ce6e56416@netapp.com>
 <20180515141721.GF12217@hirez.programming.kicks-ass.net>
CC:     Matthew Wilcox <willy@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Jeff Moyer <jmoyer@redhat.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, <x86@kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Rik van Riel <riel@redhat.com>, Jan Kara <jack@suse.cz>,
        Matthew Wilcox <mawilcox@microsoft.com>,
        Amit Golander <Amit.Golander@netapp.com>
From:   Boaz Harrosh <boazh@netapp.com>
Message-ID: <99bd469f-5cec-c537-ba3e-738956070a8f@netapp.com>
Date:   Tue, 15 May 2018 17:36:44 +0300
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101
 Thunderbird/45.4.0
MIME-Version: 1.0
In-Reply-To: <20180515141721.GF12217@hirez.programming.kicks-ass.net>
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
Received-SPF: None (protection.outlook.com: netapp.com does not designate
 permitted sender hosts)
SpamDiagnosticOutput: 1:99
SpamDiagnosticMetadata: NSPM
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 May 2018 14:36:56.2371 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: 7e6788a2-d726-4d23-ed27-08d5ba715131
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 4b0911a0-929b-4715-944b-c03745165b3a
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN6PR06MB3076
X-OriginatorOrg: netapp.com
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 15/05/18 17:17, Peter Zijlstra wrote:
<>
>>
>> So I would love some mm guy to explain where are those bits collected?
> 
> Depends on the architecture, some architectures only ever set bits,
> some, like x86, clear bits again. You want to look at switch_mm().
> 
> Basically x86 clears the bit again when we switch away from the mm and
> have/will invalidate TLBs for it in doing so.
> 

Ha, OK I am starting to get a picture.

>> Which brings me to another question. How can I find from
>> within a thread Say at the file_operations->mmap() call that the thread
>> is indeed core-pinned. What mm_cpumask should I inspect?
> 
> is_percpu_thread().

Right thank you a lot Peter. this helps.

Boaz
> .
>