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Message-ID: <1496101992.29205.77.camel@redhat.com>
Subject: Re: [PATCH v4 3/8] x86/mm: Refactor flush_tlb_mm_range() to merge
 local and remote cases
From: Rik van Riel <riel@redhat.com>
Date: Mon, 29 May 2017 19:53:12 -0400
In-Reply-To: <1496101762.29205.75.camel@redhat.com>
References: <cover.1495990440.git.luto@kernel.org>
	 <bcaf9dbdd1216b7fc03ad4870477e9772edecfc9.1495990440.git.luto@kernel.org>
	 <1496101762.29205.75.camel@redhat.com>
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To: Andy Lutomirski <luto@kernel.org>, X86 ML <x86@kernel.org>
Cc: Borislav Petkov <bpetkov@suse.de>, Linus Torvalds <torvalds@linux-foundation.org>, Andrew Morton <akpm@linux-foundation.org>, Mel Gorman <mgorman@suse.de>, "linux-mm@kvack.org" <linux-mm@kvack.org>, Nadav Amit <nadav.amit@gmail.com>, Dave Hansen <dave.hansen@intel.com>, Nadav Amit <namit@vmware.com>, Michal Hocko <mhocko@suse.com>, Arjan van de Ven <arjan@linux.intel.com>

On Mon, 2017-05-29 at 19:49 -0400, Rik van Riel wrote:
> On Sun, 2017-05-28 at 10:00 -0700, Andy Lutomirski wrote:
> 
> > +
> > +	if (mm == current->active_mm)
> > +		flush_tlb_func_local(&info,
> > TLB_LOCAL_MM_SHOOTDOWN);
> > +	if (cpumask_any_but(mm_cpumask(mm), cpu) < nr_cpu_ids)
> > A 		flush_tlb_others(mm_cpumask(mm), &info);
> 
> What excludes "cpu" from the cpumask before calling
> (native_)flush_tlb_others?
> 
> Otherwise smp_call_function_many will simply call
> flush_tbl_func_remote for the local CPU as well, and
> you get local CPU TLB flushing overhead twice.
> 
> What am I missing?

Never mind, I just re-read smp_call_function_many
for the third time, and spotted what I missed.

That function will not execute flush_tlb_func_remote
on the local cpu, and I should stop looking at code
for the day.

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