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Subject: Re: [PATCH] mm: Add new vma flag VM_LOCAL_CPU
References: <0efb5547-9250-6b6c-fe8e-cf4f44aaa5eb@netapp.com>
 <20180514144901.0fe99d240ff8a53047dd512e@linux-foundation.org>
 <20180515004406.GB5168@bombadil.infradead.org>
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 <20180515141721.GF12217@hirez.programming.kicks-ass.net>
From: Boaz Harrosh <boazh@netapp.com>
Message-ID: <99bd469f-5cec-c537-ba3e-738956070a8f@netapp.com>
Date: Tue, 15 May 2018 17:36:44 +0300
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To: Peter Zijlstra <peterz@infradead.org>, Boaz Harrosh <boazh@netapp.com>
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>

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
> .
>