linux-kernel - Re: [tip: x86/cache] x86/resctrl: Fix incorrect local bandwidth when mba

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Date:   Wed, 9 Dec 2020 23:23:28 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Xiaochen Shen <xiaochen.shen@...el.com>
Cc:     linux-tip-commits@...r.kernel.org,
        Xiaochen Shen <xiaochen.shen@...el.com>,
        Borislav Petkov <bp@...e.de>, Tony Luck <tony.luck@...el.com>,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [tip: x86/cache] x86/resctrl: Fix incorrect local bandwidth when
 mba_sc is enabled

On Wed, Dec 09, 2020 at 07:06:58PM -0000, tip-bot2 for Xiaochen Shen wrote:
> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index 622073f..93a33b7 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -320,7 +320,6 @@ static int __mon_event_count(u32 rmid, struct rmid_read *rr)
>  	}
>  
>  	chunks = mbm_overflow_count(m->prev_msr, tval, rr->r->mbm_width);
> -	m->chunks += chunks;
>  	m->prev_msr = tval;
>  
>  	rr->val += get_corrected_mbm_count(rmid, m->chunks);


Hmm, zapping this one. First, there's an unused variable warning:

https://lkml.kernel.org/r/202012100516.H7sTNehL-lkp@intel.com

and you should remove the chunks assignment too.

And then it didn't apply cleanly:

$ test-apply.sh /tmp/xiaochen.01 
checking file arch/x86/kernel/cpu/resctrl/monitor.c
Hunk #1 FAILED at 279.
Hunk #2 succeeded at 514 (offset 64 lines).
1 out of 2 hunks FAILED

I wiggled it in but it ended up removing the wrong chunks inc line -
not the one in mbm_bw_count() but in __mon_event_count() - which I just
realized.

So please redo this patch against:

https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/log/?h=x86/cache

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette