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Date:   Wed, 7 Apr 2021 16:48:44 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Michel Lespinasse <michel@lespinasse.org>
Cc:     Linux-MM <linux-mm@kvack.org>,
        Laurent Dufour <ldufour@linux.ibm.com>,
        Michal Hocko <mhocko@suse.com>,
        Matthew Wilcox <willy@infradead.org>,
        Rik van Riel <riel@surriel.com>,
        Paul McKenney <paulmck@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Suren Baghdasaryan <surenb@google.com>,
        Joel Fernandes <joelaf@google.com>,
        Rom Lemarchand <romlem@google.com>,
        Linux-Kernel <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH 11/37] x86/mm: attempt speculative mm faults first
Message-ID: <YG3GTI8j1ohk4NhS@hirez.programming.kicks-ass.net>
References: <20210407014502.24091-1-michel@lespinasse.org>
 <20210407014502.24091-12-michel@lespinasse.org>
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On Tue, Apr 06, 2021 at 06:44:36PM -0700, Michel Lespinasse wrote:
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -1219,6 +1219,8 @@ void do_user_addr_fault(struct pt_regs *regs,
>  	struct mm_struct *mm;
>  	vm_fault_t fault;
>  	unsigned int flags = FAULT_FLAG_DEFAULT;
> +	struct vm_area_struct pvma;

That's 200 bytes on-stack... I suppose that's just about acceptible, but
perhaps we need a comment in struct vm_area_struct to make people aware
this things lives on-stack and size really is an issue now.