linux-kernel - Re: [PATCH 13/16] perf: Add a speculative page fault sw events

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Message-ID: <87lgmsnalk.fsf@concordia.ellerman.id.au>
Date:   Wed, 09 Aug 2017 23:18:15 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Laurent Dufour <ldufour@...ux.vnet.ibm.com>,
        paulmck@...ux.vnet.ibm.com, peterz@...radead.org,
        akpm@...ux-foundation.org, kirill@...temov.name,
        ak@...ux.intel.com, mhocko@...nel.org, dave@...olabs.net,
        jack@...e.cz, Matthew Wilcox <willy@...radead.org>,
        benh@...nel.crashing.org, paulus@...ba.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, hpa@...or.com,
        Will Deacon <will.deacon@....com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        haren@...ux.vnet.ibm.com, khandual@...ux.vnet.ibm.com,
        npiggin@...il.com, bsingharora@...il.com,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        linuxppc-dev@...ts.ozlabs.org, x86@...nel.org
Subject: Re: [PATCH 13/16] perf: Add a speculative page fault sw events

Laurent Dufour <ldufour@...ux.vnet.ibm.com> writes:

> Add new software events to count succeeded and failed speculative page
> faults.
>
> Signed-off-by: Laurent Dufour <ldufour@...ux.vnet.ibm.com>
> ---
>  include/uapi/linux/perf_event.h | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
> index b1c0b187acfe..fbfb03dff334 100644
> --- a/include/uapi/linux/perf_event.h
> +++ b/include/uapi/linux/perf_event.h
> @@ -111,6 +111,8 @@ enum perf_sw_ids {
>  	PERF_COUNT_SW_EMULATION_FAULTS		= 8,
>  	PERF_COUNT_SW_DUMMY			= 9,
>  	PERF_COUNT_SW_BPF_OUTPUT		= 10,
> +	PERF_COUNT_SW_SPF_DONE			= 11,
> +	PERF_COUNT_SW_SPF_FAILED		= 12,

Can't you calculate:

  PERF_COUNT_SW_SPF_FAILED = PERF_COUNT_SW_PAGE_FAULTS - PERF_COUNT_SW_SPF_DONE

ie. do you need a separate event for it?

cheers