linux-kernel - Re: [PATCH 0/7] x86/mm/tlb: make lazy TLB mode even lazier

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Message-ID: <3faac660df4f52a0a4e140cd51715f0efede56d1.camel@surriel.com>
Date:   Wed, 24 Oct 2018 08:52:08 -0400
From:   Rik van Riel <riel@...riel.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        kernel-team@...com, songliubraving@...com, will.deacon@....com,
        hpa@...or.com, luto@...nel.org, npiggin@...il.com,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH 0/7] x86/mm/tlb: make lazy TLB mode even lazier

On Wed, 2018-10-24 at 07:53 +0200, Ingo Molnar wrote:
> * Rik van Riel <riel@...riel.com> wrote:
> 
> > The big thing remaining is the reference count overhead of
> > the lazy TLB mm_struct, but getting rid of that is rather a
> > lot of code for a small performance gain. Not quite what
> > Linus asked for :)
> 
> BTW., what would be the plan to improve scalability there,
> is it even possible?

One thing I looked at was shooting down the lazy TLB
MM from the exit code path, that way the MM would no
longer be referenced from any CPU by the time the
memory gets freed.

Once we do that, we no longer need to do any refcounting
for the lazy TLB MM.

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