linux-kernel - [PATCH v6 1/5] perf: Add SNOOP_PEER flag to perf mem data struct

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Date:   Tue, 26 Apr 2022 01:59:22 +0000
From:   Ali Saidi <alisaidi@...zon.com>
To:     <linux-kernel@...r.kernel.org>, <linux-perf-users@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <german.gomez@....com>,
        <leo.yan@...aro.org>, <acme@...nel.org>
CC:     <alisaidi@...zon.com>, <benh@...nel.crashing.org>,
        <Nick.Forrington@....com>, <alexander.shishkin@...ux.intel.com>,
        <andrew.kilroy@....com>, <james.clark@....com>,
        <john.garry@...wei.com>, <jolsa@...nel.org>, <kjain@...ux.ibm.com>,
        <lihuafei1@...wei.com>, <mark.rutland@....com>,
        <mathieu.poirier@...aro.org>, <mingo@...hat.com>,
        <namhyung@...nel.org>, <peterz@...radead.org>, <will@...nel.org>
Subject: [PATCH v6 1/5] perf: Add SNOOP_PEER flag to perf mem data struct

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.

Signed-off-by: Ali Saidi <alisaidi@...zon.com>
Reviewed-by: Leo Yan <leo.yan@...aro.org>
---
 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 d37629dbad72..7b88bfd097dc 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -1310,7 +1310,7 @@ 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 */
-- 
2.32.0