From 391b170f10e669dd429aa47bce998c2fa839404c Mon Sep 17 00:00:00 2001 From: Pekka Paalanen Date: Tue, 6 Jan 2009 13:57:11 +0200 Subject: [PATCH 1/3] mmiotrace: count events lost due to not recording Impact: enhances lost events counting in mmiotrace The tracing framework, or the ring buffer facility it uses, has a switch to stop recording data. When recording is off, the trace events will be lost. The framework does not count these, so mmiotrace has to count them itself. Signed-off-by: Pekka Paalanen Signed-off-by: Steven Rostedt Signed-off-by: Ingo Molnar --- kernel/trace/trace_mmiotrace.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/kernel/trace/trace_mmiotrace.c b/kernel/trace/trace_mmiotrace.c index fffcb069f1dc..80e503ef6136 100644 --- a/kernel/trace/trace_mmiotrace.c +++ b/kernel/trace/trace_mmiotrace.c @@ -9,6 +9,7 @@ #include #include #include +#include #include "trace.h" @@ -19,6 +20,7 @@ struct header_iter { static struct trace_array *mmio_trace_array; static bool overrun_detected; static unsigned long prev_overruns; +static atomic_t dropped_count; static void mmio_reset_data(struct trace_array *tr) { @@ -121,11 +123,11 @@ static void mmio_close(struct trace_iterator *iter) static unsigned long count_overruns(struct trace_iterator *iter) { - unsigned long cnt = 0; + unsigned long cnt = atomic_xchg(&dropped_count, 0); unsigned long over = ring_buffer_overruns(iter->tr->buffer); if (over > prev_overruns) - cnt = over - prev_overruns; + cnt += over - prev_overruns; prev_overruns = over; return cnt; } @@ -310,8 +312,10 @@ static void __trace_mmiotrace_rw(struct trace_array *tr, event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry), &irq_flags); - if (!event) + if (!event) { + atomic_inc(&dropped_count); return; + } entry = ring_buffer_event_data(event); tracing_generic_entry_update(&entry->ent, 0, preempt_count()); entry->ent.type = TRACE_MMIO_RW; @@ -338,8 +342,10 @@ static void __trace_mmiotrace_map(struct trace_array *tr, event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry), &irq_flags); - if (!event) + if (!event) { + atomic_inc(&dropped_count); return; + } entry = ring_buffer_event_data(event); tracing_generic_entry_update(&entry->ent, 0, preempt_count()); entry->ent.type = TRACE_MMIO_MAP; From 6bc5c366b1a45ca18fba6851f62db5743b3f6db5 Mon Sep 17 00:00:00 2001 From: Pekka Paalanen Date: Sat, 3 Jan 2009 21:23:51 +0200 Subject: [PATCH 2/3] trace: mmiotrace to the tracer menu in Kconfig Impact: cosmetic change in Kconfig menu layout This patch was originally suggested by Peter Zijlstra, but seems it was forgotten. CONFIG_MMIOTRACE and CONFIG_MMIOTRACE_TEST were selectable directly under the Kernel hacking / debugging menu in the kernel configuration system. They were present only for x86 and x86_64. Other tracers that use the ftrace tracing framework are in their own sub-menu. This patch moves the mmiotrace configuration options there. Since the Kconfig file, where the tracer menu is, is not architecture specific, HAVE_MMIOTRACE_SUPPORT is introduced and provided only by x86/x86_64. CONFIG_MMIOTRACE now depends on it. Signed-off-by: Pekka Paalanen Signed-off-by: Steven Rostedt Signed-off-by: Ingo Molnar --- arch/x86/Kconfig.debug | 24 ++---------------------- kernel/trace/Kconfig | 23 +++++++++++++++++++++++ 2 files changed, 25 insertions(+), 22 deletions(-) diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug index 10d6cc3fd052..e1983fa025d2 100644 --- a/arch/x86/Kconfig.debug +++ b/arch/x86/Kconfig.debug @@ -174,28 +174,8 @@ config IOMMU_LEAK Add a simple leak tracer to the IOMMU code. This is useful when you are debugging a buggy device driver that leaks IOMMU mappings. -config MMIOTRACE - bool "Memory mapped IO tracing" - depends on DEBUG_KERNEL && PCI - select TRACING - help - Mmiotrace traces Memory Mapped I/O access and is meant for - debugging and reverse engineering. It is called from the ioremap - implementation and works via page faults. Tracing is disabled by - default and can be enabled at run-time. - - See Documentation/tracers/mmiotrace.txt. - If you are not helping to develop drivers, say N. - -config MMIOTRACE_TEST - tristate "Test module for mmiotrace" - depends on MMIOTRACE && m - help - This is a dumb module for testing mmiotrace. It is very dangerous - as it will write garbage to IO memory starting at a given address. - However, it should be safe to use on e.g. unused portion of VRAM. - - Say N, unless you absolutely know what you are doing. +config HAVE_MMIOTRACE_SUPPORT + def_bool y # # IO delay types: diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig index e2a4ff6fc3a6..58a93fbd68aa 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -302,4 +302,27 @@ config FTRACE_STARTUP_TEST functioning properly. It will do tests on all the configured tracers of ftrace. +config MMIOTRACE + bool "Memory mapped IO tracing" + depends on HAVE_MMIOTRACE_SUPPORT && DEBUG_KERNEL && PCI + select TRACING + help + Mmiotrace traces Memory Mapped I/O access and is meant for + debugging and reverse engineering. It is called from the ioremap + implementation and works via page faults. Tracing is disabled by + default and can be enabled at run-time. + + See Documentation/tracers/mmiotrace.txt. + If you are not helping to develop drivers, say N. + +config MMIOTRACE_TEST + tristate "Test module for mmiotrace" + depends on MMIOTRACE && m + help + This is a dumb module for testing mmiotrace. It is very dangerous + as it will write garbage to IO memory starting at a given address. + However, it should be safe to use on e.g. unused portion of VRAM. + + Say N, unless you absolutely know what you are doing. + endmenu From f9aa28adfc6a4b01268ebb6d88566cca8627905f Mon Sep 17 00:00:00 2001 From: Pekka Paalanen Date: Sat, 3 Jan 2009 21:09:27 +0200 Subject: [PATCH 3/3] doc: mmiotrace.txt, buffer size control change Impact: prevents confusing the user when buffer size is inadequate The tracing framework offers a resizeable buffer, which mmiotrace uses to record events. If the buffer is full, the following events will be lost. Events should not be lost, so the documentation instructs the user to increase the buffer size. The buffer size is set via a debugfs file. Mmiotrace documentation was not updated the same time the debugfs file was changed. The old file was tracing/trace_entries and first contained the number of entries the buffer had space for, per cpu. Nowadays this file is replaced with the file tracing/buffer_size_kb, which tells the amount of memory reserved for the buffer, per cpu, in kilobytes. Previously, a flag had to be toggled via the debugfs file tracing/tracing_enabled when the buffer size was changed. This is no longer necessary. The mmiotrace documentation is updated to reflect the current state of the tracing framework. Signed-off-by: Pekka Paalanen Signed-off-by: Steven Rostedt Signed-off-by: Ingo Molnar --- Documentation/tracers/mmiotrace.txt | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/Documentation/tracers/mmiotrace.txt b/Documentation/tracers/mmiotrace.txt index cde23b4a12a1..5731c67abc55 100644 --- a/Documentation/tracers/mmiotrace.txt +++ b/Documentation/tracers/mmiotrace.txt @@ -78,12 +78,10 @@ to view your kernel log and look for "mmiotrace has lost events" warning. If events were lost, the trace is incomplete. You should enlarge the buffers and try again. Buffers are enlarged by first seeing how large the current buffers are: -$ cat /debug/tracing/trace_entries +$ cat /debug/tracing/buffer_size_kb gives you a number. Approximately double this number and write it back, for instance: -$ echo 0 > /debug/tracing/tracing_enabled -$ echo 128000 > /debug/tracing/trace_entries -$ echo 1 > /debug/tracing/tracing_enabled +$ echo 128000 > /debug/tracing/buffer_size_kb Then start again from the top. If you are doing a trace for a driver project, e.g. Nouveau, you should also