Messages in this thread | | | Date | Wed, 20 Apr 2022 14:43:28 -0400 | Subject | Re: [PATCH v5 2/5] perf: Add SNOOP_PEER flag to perf mem data struct | From | "Liang, Kan" <> |
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On 4/8/2022 3:53 PM, Ali Saidi wrote: > 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.
It sounds similar to the Forward state. Why can't the PERF_MEM_SNOOPX_FWD be reused?
Thanks, Kan
> 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@amazon.com> > --- > 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 82858b697c05..c9e58c79f3e5 100644 > --- a/include/uapi/linux/perf_event.h > +++ b/include/uapi/linux/perf_event.h > @@ -1308,7 +1308,7 @@ 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 */
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