linux-kernel - Re: [PATCH v3 0/5] perf: arm_spe: Add format option for discard mode

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Message-ID: <5ea201e5-6ab7-4935-a8ce-20f67f3193c1@linaro.org>
Date: Mon, 13 Jan 2025 14:33:46 +0000
From: James Clark <james.clark@...aro.org>
To: Will Deacon <will@...nel.org>, namhyung@...nel.org, acme@...nel.org
Cc: catalin.marinas@....com, kernel-team@...roid.com, robh@...nel.org,
 Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Jiri Olsa <jolsa@...nel.org>, Adrian Hunter <adrian.hunter@...el.com>,
 "Liang, Kan" <kan.liang@...ux.intel.com>,
 John Garry <john.g.garry@...cle.com>, Mike Leach <mike.leach@...aro.org>,
 Leo Yan <leo.yan@...ux.dev>, Graham Woodward <graham.woodward@....com>,
 Michael Petlan <mpetlan@...hat.com>, Veronika Molnarova
 <vmolnaro@...hat.com>, Thomas Richter <tmricht@...ux.ibm.com>,
 Athira Rajeev <atrajeev@...ux.vnet.ibm.com>, linux-kernel@...r.kernel.org,
 bpf@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-perf-users@...r.kernel.org, irogers@...gle.com, yeoreum.yun@....com,
 mark.rutland@....com
Subject: Re: [PATCH v3 0/5] perf: arm_spe: Add format option for discard mode



On 10/01/2025 4:22 pm, Will Deacon wrote:
> On Wed, 08 Jan 2025 14:28:55 +0000, James Clark wrote:
>> Discard mode (Armv8.6) is a way to enable SPE related PMU events without
>> the overhead of recording any data. Add a format option, tests and docs
>> for it.
>>
>> In theory we could make the driver drop calls to allocate the aux buffer
>> when discard mode is enabled. This would give a small memory saving,
>> but I think there is potential to interfere with any tools that don't
>> expect this so I left the aux allocation untouched. Even old tools that
>> don't know about discard mode will be able to use it because we publish
>> the format option. Not allocating the aux buffer will have to be added
>> to tools which I've done in Perf.
>>
>> [...]
> 
> Applied driver and docs patches to will (for-next/perf), thanks!
> 
> [1/5] perf: arm_spe: Add format option for discard mode
>        https://git.kernel.org/will/c/d28d95bc63cb
> [2/5] perf docs: arm_spe: Document new discard mode
>        https://git.kernel.org/will/c/ba113ecad81a
> 
> Cheers,

Thanks Will. Arnaldo and Namhyung, are you ok to take the Perf changes now?

Thanks
James