From: Peter Zijlstra <peterz@infradead.org>
To: Rik van Riel <riel@surriel.com>
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: Mon, 6 Aug 2018 19:50:13 +0200 [thread overview]
Message-ID: <20180806175013.GB2476@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <1533317992.28585.103.camel@surriel.com>
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On Fri, Aug 03, 2018 at 01:39:52PM -0400, Rik van Riel wrote:
> > 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.
They hint at it :-)
> What is missing from my explanation?
> How would you like to see it explained?
Maybe a few words like:
"Since ->active_mm is still used in a few sites, we must keep the
current tracking, such that we will not hit a kthread's NULL mm. Note
that lazy_tlb_exit_mmap() switches ->active_mm to &init_mm before taking
out the lazy mm."
That said; I'm not entirely sure we'll actually touch active_mm if we're
not a user task. The perf thing for example will only touch active_mm
when user_mode(regs).
But whatever, this was the only hickup.
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
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prev parent reply other threads:[~2018-08-06 17:50 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
2018-08-06 17:50 ` Peter Zijlstra [this message]
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