linux-kernel - Re: [v4 0/3] Reduce TLB flushes under some specific conditions

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Date:   Fri, 10 Nov 2023 10:08:52 +0900
From:   Byungchul Park <byungchul@...com>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        kernel_team@...ynix.com, akpm@...ux-foundation.org,
        ying.huang@...el.com, namit@...are.com, xhao@...ux.alibaba.com,
        mgorman@...hsingularity.net, hughd@...gle.com, willy@...radead.org,
        david@...hat.com, peterz@...radead.org, luto@...nel.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com
Subject: Re: [v4 0/3] Reduce TLB flushes under some specific conditions

On Thu, Nov 09, 2023 at 06:26:08AM -0800, Dave Hansen wrote:
> On 11/8/23 20:59, Byungchul Park wrote:
> > Can you believe it? I saw the number of TLB full flush reduced about
> > 80% and iTLB miss reduced about 50%, and the time wise performance
> > always shows at least 1% stable improvement with the workload I tested
> > with, XSBench. However, I believe that it would help more with other
> > ones or any real ones. It'd be appreciated to let me know if I'm missing
> > something.
> 
> I see that you've moved a substantial amount of code out of arch/x86.
> That's great.
> 
> But there doesn't appear to be any improvement in the justification or
> performance data.  The page flag is also here, which is horribly frowned
> upon.  It's an absolute no-go with this level of justification.
> 
> I'd really suggest not sending any more of these out until those issues
> are rectified.  I know I definitely won't be reviewing them in this state.

Make sense. Lemme think it more and improve it.

	Byungchul