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From: Rik van Riel <riel@surriel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
	mingo@kernel.org, luto@kernel.org, x86@kernel.org, efault@gmx.de,
	dave.hansen@intel.com
Subject: Re: [PATCH 11/11] mm,sched: conditionally skip lazy TLB mm refcounting
Date: Fri, 03 Aug 2018 13:39:52 -0400	[thread overview]
Message-ID: <1533317992.28585.103.camel@surriel.com> (raw)
In-Reply-To: <20180803172516.GM2458@hirez.programming.kicks-ass.net>

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On Fri, 2018-08-03 at 19:25 +0200, Peter Zijlstra wrote:
> On Fri, Aug 03, 2018 at 12:40:48PM -0400, Rik van Riel wrote:
> > On Fri, 2018-08-03 at 17:56 +0200, Peter Zijlstra wrote:
> > > 
> > > Why can't we skip the ->active_mm swizzle and keep ->active_mm ==
> > > ->mm.
> > > 
> > > Doing the swizzle but not the refcount just makes me itch.
> > 
> > I am working on that now, it adds another 7-8
> > patches on top of this series.
> 
> I thought those were taking ->active_mm out entirely, not avoiding
> the
> swizzle, but I might have missed something in the middle :-)

At this point, only the fact that ->active_mm is still
being used by a few places in the code :)

> > The big question is, do we want this optimization
> > to wait for further cleanups, or should we run with
> > code that seems to be stable right now, and put
> > additional cleanups and enhancements on top of it
> > later?
> 
> At the very least the Changelog needs to explain why we cannot do
> away
> with the swizzle now and how doing the swizzle without the
> refcounting
> is not completely broken (I think I see, but urgh).

The changelog for patches 9 & 10 explains, I think.

What is missing from my explanation?

How would you like to see it explained?

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All Rights Reversed.

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  reply	other threads:[~2018-08-03 17:39 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-01 10:02 [PATCH v2 0/11] x86,tlb,mm: more lazy TLB cleanups & optimizations Rik van Riel
2018-08-01 10:02 ` [PATCH 01/11] x86,tlb: clarify memory barrier in switch_mm_irqs_off Rik van Riel
2018-08-01 10:02 ` [PATCH 02/11] smp: use __cpumask_set_cpu in on_each_cpu_cond Rik van Riel
2018-08-01 10:02 ` [PATCH 03/11] smp,cpumask: introduce on_each_cpu_cond_mask Rik van Riel
2018-08-01 10:02 ` [PATCH 04/11] x86,mm: use on_each_cpu_cond for TLB flushes Rik van Riel
2018-08-01 10:02 ` [PATCH 05/11] mm,tlb: turn dummy defines into inline functions Rik van Riel
2018-08-01 10:02 ` [PATCH 06/11] mm,x86: skip cr4 and ldt reload when mm stays the same Rik van Riel
2018-08-01 10:02 ` [PATCH 07/11] x86,mm: remove leave_mm cpu argument Rik van Riel
2018-08-01 10:02 ` [PATCH 08/11] arch,mm: add config variable to skip lazy TLB mm refcounting Rik van Riel
2018-08-01 10:02 ` [PATCH 09/11] mm,x86: shoot down lazy TLB references at exit_mmap time Rik van Riel
2018-08-01 10:02 ` [PATCH 10/11] x86,tlb: really leave mm on shootdown Rik van Riel
2018-08-01 10:02 ` [PATCH 11/11] mm,sched: conditionally skip lazy TLB mm refcounting Rik van Riel
2018-08-03 15:56   ` Peter Zijlstra
2018-08-03 16:40     ` Rik van Riel
2018-08-03 17:25       ` Peter Zijlstra
2018-08-03 17:39         ` Rik van Riel [this message]
2018-08-06 17:50           ` Peter Zijlstra

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