linux-kernel - Re: [PATCH 4/7] x86,tlb: make lazy TLB mode lazier

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Date:   Fri, 20 Jul 2018 13:04:24 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Andy Lutomirski <luto@...capital.net>
Cc:     Rik van Riel <riel@...riel.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Mike Galbraith <efault@....de>,
        kernel-team <kernel-team@...com>, Ingo Molnar <mingo@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>
Subject: Re: [PATCH 4/7] x86,tlb: make lazy TLB mode lazier

On Fri, Jul 20, 2018 at 11:32:39AM +0200, Peter Zijlstra wrote:

> +	if (!next->mm) {				// to kernel
> +		enter_lazy_tlb(prev->active_mm, next);
> +
> +#ifdef ARCH_NO_ACTIVE_MM
> +		next->active_mm = prev->active_mm;
> +		if (prev->mm)				// from user
> +			mmgrab(prev->active_mm);
		else
			prev->active_mm = NULL;
> +#endif
> +	} else {					// to user
> +		switch_mm_irqs_off(prev->active_mm, next->mm, next);
> +
> +#ifdef ARCH_NO_ACTIVE_MM
> +		if (!prev->mm) {			// from kernel
> +			/* will mmdrop() in finish_task_switch(). */
> +			rq->prev_mm = prev->active_mm;
> +			prev->active_mm = NULL;
> +		}
> +#endif
>  	}