linux-kernel - Re: [PATCH] perf_events: fix and improve x86 event scheduling

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 10 Nov 2011 15:37:40 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	linux-kernel@...r.kernel.org, robert.richter@....com,
	mingo@...e.hu, ming.m.lin@...el.com, ak@...ux.intel.com
Subject: Re: [PATCH] perf_events: fix and improve x86 event scheduling

Just throwing this out there (hasn't event been compiled etc..).

The idea is to try the fixed counters first so that we don't
'accidentally' fill a GP counter with something that could have lived on
the fixed purpose one and then end up under utilizing the PMU that way.

It ought to solve the most common PMU programming fail on Intel
thingies.

---
Index: linux-2.6/arch/x86/kernel/cpu/perf_event.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/cpu/perf_event.c
+++ linux-2.6/arch/x86/kernel/cpu/perf_event.c
@@ -558,14 +558,22 @@ int x86_schedule_events(struct cpu_hw_ev
 			if (c->weight != w)
 				continue;
 
-			for_each_set_bit(j, c->idxmsk, X86_PMC_IDX_MAX) {
+			if (x86_pmu.num_counters_fixed) {
+				j = X86_PMC_IDX_FIXED - 1;
+				for_each_set_bit_cont(j, c->idxmsk, X86_PMC_IDX_MAX) {
+					if (!test_bit(k, used_mask))
+						goto assign;
+				}
+			}
+
+			for_each_set_bit(j, c->idxmsk, X86_PMC_IDX_FIXED) {
 				if (!test_bit(j, used_mask))
-					break;
+					goto assign;
 			}
 
-			if (j == X86_PMC_IDX_MAX)
-				break;
+			break;
 
+assign:
 			__set_bit(j, used_mask);
 
 			if (assign)
Index: linux-2.6/include/linux/bitops.h
===================================================================
--- linux-2.6.orig/include/linux/bitops.h
+++ linux-2.6/include/linux/bitops.h
@@ -26,6 +26,12 @@ extern unsigned long __sw_hweight64(__u6
 	     (bit) < (size); \
 	     (bit) = find_next_bit((addr), (size), (bit) + 1))
 
+#define for_each_set_bit_cont(bit, addr, size) \
+	for ((bit) = find_next_bit((addr), (size), (bit) + 1); \
+	     (bit) < (size); \
+	     (bit) = find_next_bit((addr), (size), (bit) + 1))
+
+
 static __inline__ int get_bitmask_order(unsigned int count)
 {
 	int order;

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/