linux-kernel - Re: [Patch v3 10/22] perf/x86/intel: Process arch-PEBS records or record fragments

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Message-ID: <7dae1dbe-02fb-4294-90b8-0c4b2aa7d70a@linux.intel.com>
Date: Tue, 15 Apr 2025 12:09:29 -0400
From: "Liang, Kan" <kan.liang@...ux.intel.com>
To: Peter Zijlstra <peterz@...radead.org>,
 Dapeng Mi <dapeng1.mi@...ux.intel.com>
Cc: Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo
 <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
 Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Andi Kleen <ak@...ux.intel.com>, Eranian Stephane <eranian@...gle.com>,
 linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
 Dapeng Mi <dapeng1.mi@...el.com>
Subject: Re: [Patch v3 10/22] perf/x86/intel: Process arch-PEBS records or
 record fragments



On 2025-04-15 9:57 a.m., Peter Zijlstra wrote:
> On Tue, Apr 15, 2025 at 11:44:16AM +0000, Dapeng Mi wrote:
>> A significant difference with adaptive PEBS is that arch-PEBS record
>> supports fragments which means an arch-PEBS record could be split into
>> several independent fragments which have its own arch-PEBS header in
>> each fragment.
> 
> With the constraint that all fragments for a single event are
> contiguous, right?

Yes. If a record is split into n fragments, the first n-1 fragments will
have the CONTINUED bit set and the last fragment will have its CONTINUED
bit cleared. They are contiguous.

Thanks,
Kan