From 1ce19bf90bd55bf54f9ed75d594029db63d395b0 Mon Sep 17 00:00:00 2001 From: Uros Bizjak Date: Mon, 7 Aug 2023 16:51:14 +0200 Subject: [PATCH] perf/x86/rapl: Stop doing cpu_relax() in the local64_cmpxchg() loop in rapl_event_update() According to the following commit: f5fe24ef17b5 ("lockref: stop doing cpu_relax in the cmpxchg loop") "On the x86-64 architecture even a failing cmpxchg grants exclusive access to the cacheline, making it preferable to retry the failed op immediately instead of stalling with the pause instruction." Based on the above observation, remove cpu_relax() from the local64_cmpxchg() loop of rapl_event_update(). Signed-off-by: Uros Bizjak Signed-off-by: Ingo Molnar Cc: Peter Zijlstra Cc: Linus Torvalds Cc: "H. Peter Anvin" Link: https://lore.kernel.org/r/20230807145134.3176-1-ubizjak@gmail.com --- arch/x86/events/rapl.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/arch/x86/events/rapl.c b/arch/x86/events/rapl.c index 1579429846cc..e8f53b2590a5 100644 --- a/arch/x86/events/rapl.c +++ b/arch/x86/events/rapl.c @@ -184,10 +184,8 @@ again: rdmsrl(event->hw.event_base, new_raw_count); if (local64_cmpxchg(&hwc->prev_count, prev_raw_count, - new_raw_count) != prev_raw_count) { - cpu_relax(); + new_raw_count) != prev_raw_count) goto again; - } /* * Now we have the new raw value and have updated the prev