From 339ce1a4dc2ca26444c4f65c31b71a5056f3bb0b Mon Sep 17 00:00:00 2001 From: Anton Blanchard Date: Mon, 18 Jan 2010 16:47:07 +1100 Subject: [PATCH] perf: Fix inconsistency between IP and callchain sampling When running perf across all cpus with backtracing (-a -g), sometimes we get samples without associated backtraces: 23.44% init [kernel] [k] restore 11.46% init eeba0c [k] 0x00000000eeba0c 6.77% swapper [kernel] [k] .perf_ctx_adjust_freq 5.73% init [kernel] [k] .__trace_hcall_entry 4.69% perf libc-2.9.so [.] 0x0000000006bb8c | |--11.11%-- 0xfffa941bbbc It turns out the backtrace code has a check for the idle task and the IP sampling does not. This creates problems when profiling an interrupt heavy workload (in my case 10Gbit ethernet) since we get no backtraces for interrupts received while idle (ie most of the workload). Right now x86 and sh check that current is not NULL, which should never happen so remove that too. Idle task's exclusion must be performed from the core code, on top of perf_event_attr:exclude_idle. Signed-off-by: Anton Blanchard Cc: Peter Zijlstra Cc: Paul Mackerras Cc: Ingo Molnar Cc: Benjamin Herrenschmidt Cc: Paul Mundt LKML-Reference: <20100118054707.GT12666@kryten> Signed-off-by: Frederic Weisbecker --- arch/powerpc/kernel/perf_callchain.c | 3 --- arch/sh/kernel/perf_callchain.c | 3 --- arch/x86/kernel/cpu/perf_event.c | 3 --- 3 files changed, 9 deletions(-) diff --git a/arch/powerpc/kernel/perf_callchain.c b/arch/powerpc/kernel/perf_callchain.c index a3c11cac3d71..95ad9dad298e 100644 --- a/arch/powerpc/kernel/perf_callchain.c +++ b/arch/powerpc/kernel/perf_callchain.c @@ -495,9 +495,6 @@ struct perf_callchain_entry *perf_callchain(struct pt_regs *regs) entry->nr = 0; - if (current->pid == 0) /* idle task? */ - return entry; - if (!user_mode(regs)) { perf_callchain_kernel(regs, entry); if (current->mm) diff --git a/arch/sh/kernel/perf_callchain.c b/arch/sh/kernel/perf_callchain.c index 24ea837eac5b..a9dd3abde28e 100644 --- a/arch/sh/kernel/perf_callchain.c +++ b/arch/sh/kernel/perf_callchain.c @@ -68,9 +68,6 @@ perf_do_callchain(struct pt_regs *regs, struct perf_callchain_entry *entry) is_user = user_mode(regs); - if (!current || current->pid == 0) - return; - if (is_user && current->state != TASK_RUNNING) return; diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c index b1bb8c550526..ed1998b28a7c 100644 --- a/arch/x86/kernel/cpu/perf_event.c +++ b/arch/x86/kernel/cpu/perf_event.c @@ -2425,9 +2425,6 @@ perf_do_callchain(struct pt_regs *regs, struct perf_callchain_entry *entry) is_user = user_mode(regs); - if (!current || current->pid == 0) - return; - if (is_user && current->state != TASK_RUNNING) return; -- 2.20.1