linux-kernel - Re: [PATCH] x86/mm/tlb: ignore f->new_tlb

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Message-ID: <a486ad3f-8fb6-c37b-9e7e-c6ba1a841b57@intel.com>
Date:   Fri, 8 Jul 2022 10:01:37 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Nadav Amit <namit@...are.com>
Cc:     David Hildenbrand <david@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Hugh Dickins <hughd@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        X86 ML <x86@...nel.org>, Linux MM <linux-mm@...ck.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH] x86/mm/tlb: ignore f->new_tlb_gen when zero

On 7/8/22 09:54, Nadav Amit wrote:
> Since the bug was not during MADV_DONTNEED there is no reason for the
> results to be any different.
> 
> Famous last words?

Considering that your patch broke the kernel a way that surprised us
all, I think caution is warranted.  Re-running a microbenchmark that
takes five minutes and stresses things a bit is the least you can do, I
think.