linux-kernel - [PATCH v7] perf: Add SNOOP_PEER flag to perf mem data struct

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Message-Id: <20220826060556.176681-1-leo.yan@linaro.org>
Date:   Fri, 26 Aug 2022 14:05:56 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Ali Saidi <alisaidi@...zon.com>, Leo Yan <leo.yan@...aro.org>,
        Kajol Jain <kjain@...ux.ibm.com>
Subject: [PATCH v7] perf: Add SNOOP_PEER flag to perf mem data struct

From: Ali Saidi <alisaidi@...zon.com>

Add a flag to the perf mem data struct to signal that a request caused a
cache-to-cache transfer of a line from a peer of the requestor and
wasn't sourced from a lower cache level.  The line being moved from one
peer cache to another has latency and performance implications. On Arm64
Neoverse systems the data source can indicate a cache-to-cache transfer
but not if the line is dirty or clean, so instead of overloading HITM
define a new flag that indicates this type of transfer.

Update notes:

This patch is to sync the headers between kernel and user space, commit
2e21bcf0514a ("perf tools: Sync addition of PERF_MEM_SNOOPX_PEER") for
updating kernel header has been merged in the mainline code.

Signed-off-by: Ali Saidi <alisaidi@...zon.com>
Reviewed-by: Leo Yan <leo.yan@...aro.org>
Reviewed-by: Kajol Jain<kjain@...ux.ibm.com>
Signed-off-by: Leo Yan <leo.yan@...aro.org>
---

Changes from v6:
Added Leo's SoB.

 include/uapi/linux/perf_event.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 03b370062741..581ed4bdc062 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -1313,7 +1313,7 @@ union perf_mem_data_src {
 #define PERF_MEM_SNOOP_SHIFT	19

 #define PERF_MEM_SNOOPX_FWD	0x01 /* forward */
-/* 1 free */
+#define PERF_MEM_SNOOPX_PEER	0x02 /* xfer from peer */
 #define PERF_MEM_SNOOPX_SHIFT  38

 /* locked instruction */
-- 
2.34.1