user/sven/linux.git/kernel/trace/ring_buffer.c, branch v3.4.92

ring-buffer: Fix first commit on sub-buffer having non-zero delta

2014-02-22T18:32:46Z

commit d651aa1d68a2f0a7ee65697b04c6a92f8c0a12f2 upstream. Each sub-buffer (buffer page) has a full 64 bit timestamp. The events on that page use a 27 bit delta against that timestamp in order to save on bits written to the ring buffer. If the time between events is larger than what the 27 bits can hold, a "time extend" event is added to hold the entire 64 bit timestamp again and the events after that hold a delta from that timestamp. As a "time extend" is always paired with an event, it is logical to just allocate the event with the time extend, to make things a bit more efficient. Unfortunately, when the pairing code was written, it removed the "delta = 0" from the first commit on a page, causing the events on the page to be slightly skewed. Fixes: 69d1b839f7ee "ring-buffer: Bind time extend and data events together" Signed-off-by: Steven Rostedt Signed-off-by: Greg Kroah-Hartman

ring-buffer: Fix race between integrity check and readers

2013-01-17T16:50:51Z

commit 9366c1ba13fbc41bdb57702e75ca4382f209c82f upstream. The function rb_check_pages() was added to make sure the ring buffer's pages were sane. This check is done when the ring buffer size is modified as well as when the iterator is released (closing the "trace" file), as that was considered a non fast path and a good place to do a sanity check. The problem is that the check does not have any locks around it. If one process were to read the trace file, and another were to read the raw binary file, the check could happen while the reader is reading the file. The issues with this is that the check requires to clear the HEAD page before doing the full check and it restores it afterward. But readers require the HEAD page to exist before it can read the buffer, otherwise it gives a nasty warning and disables the buffer. By adding the reader lock around the check, this keeps the race from happening. Signed-off-by: Steven Rostedt Signed-off-by: Greg Kroah-Hartman

tracing/ring-buffer: Only have tracing_on disable tracing buffers

2012-02-22T20:50:28Z

As the ring-buffer code is being used by other facilities in the kernel, having tracing_on file disable *all* buffers is not a desired affect. It should only disable the ftrace buffers that are being used. Move the code into the trace.c file and use the buffer disabling for tracing_on() and tracing_off(). This way only the ftrace buffers will be affected by them and other kernel utilities will not be confused to why their output suddenly stopped. Signed-off-by: Steven Rostedt

Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2011-10-26T15:03:38Z

* 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (121 commits) perf symbols: Increase symbol KSYM_NAME_LEN size perf hists browser: Refuse 'a' hotkey on non symbolic views perf ui browser: Use libslang to read keys perf tools: Fix tracing info recording perf hists browser: Elide DSO column when it is set to just one DSO, ditto for threads perf hists: Don't consider filtered entries when calculating column widths perf hists: Don't decay total_period for filtered entries perf hists browser: Honour symbol_conf.show_{nr_samples,total_period} perf hists browser: Do not exit on tab key with single event perf annotate browser: Don't change selection line when returning from callq perf tools: handle endianness of feature bitmap perf tools: Add prelink suggestion to dso update message perf script: Fix unknown feature comment perf hists browser: Apply the dso and thread filters when merging new batches perf hists: Move the dso and thread filters from hist_browser perf ui browser: Honour the xterm colors perf top tui: Give color hints just on the percentage, like on --stdio perf ui browser: Make the colors configurable and change the defaults perf tui: Remove unneeded call to newtCls on startup perf hists: Don't format the percentage on hist_entry__snprintf ... Fix up conflicts in arch/x86/kernel/kprobes.c manually. Ingo's tree did the insane "add volatile to const array", which just doesn't make sense ("volatile const"?). But we could remove the const *and* make the array volatile to make doubly sure that gcc doesn't optimize it away.. Also fix up kernel/trace/ring_buffer.c non-data-conflicts manually: the reader_lock has been turned into a raw lock by the core locking merge, and there was a new user of it introduced in this perf core merge. Make sure that new use also uses the raw accessor functions.

locking, tracing: Annotate tracing locks as raw

2011-09-13T09:11:52Z

The tracing locks can be taken in atomic context and therefore cannot be preempted on -rt - annotate it. In mainline this change documents the low level nature of the lock - otherwise there's no functional difference. Lockdep and Sparse checking will work as usual. Signed-off-by: Thomas Gleixner Signed-off-by: Ingo Molnar

trace: Add ring buffer stats to measure rate of events

2011-08-30T16:27:45Z

The stats file under per_cpu folder provides the number of entries, overruns and other statistics about the CPU ring buffer. However, the numbers do not provide any indication of how full the ring buffer is in bytes compared to the overall size in bytes. Also, it is helpful to know the rate at which the cpu buffer is filling up. This patch adds an entry "bytes: " in printed stats for per_cpu ring buffer which provides the actual bytes consumed in the ring buffer. This field includes the number of bytes used by recorded events and the padding bytes added when moving the tail pointer to next page. It also adds the following time stamps: "oldest event ts:" - the oldest timestamp in the ring buffer "now ts:" - the timestamp at the time of reading The field "now ts" provides a consistent time snapshot to the userspace when being read. This is read from the same trace clock used by tracing event timestamps. Together, these values provide the rate at which the buffer is filling up, from the formula: bytes / (now_ts - oldest_event_ts) Signed-off-by: Vaibhav Nagarnaik Cc: Michael Rubin Cc: David Sharp Link: http://lkml.kernel.org/r/1313531179-9323-3-git-send-email-vnagarnaik@google.com Signed-off-by: Steven Rostedt

ring-buffer: Set __GFP_NORETRY flag for ring buffer allocating process

2011-06-15T02:48:51Z

The tracing ring buffer is allocated from kernel memory. While allocating a large chunk of memory, OOM might happen which destabilizes the system. Thus random processes might get killed during the allocation. This patch adds __GFP_NORETRY flag to the ring buffer allocation calls to make it fail more gracefully if the system will not be able to complete the allocation request. Acked-by: David Rientjes Signed-off-by: Vaibhav Nagarnaik Cc: Ingo Molnar Cc: Frederic Weisbecker Cc: Michael Rubin Cc: David Sharp Link: http://lkml.kernel.org/r/1307491302-9236-1-git-send-email-vnagarnaik@google.com Signed-off-by: Steven Rostedt

tracing: Convert to kstrtoul_from_user

2011-06-15T02:48:50Z

This patch replaces the code for getting an unsigned long from a userspace buffer by a simple call to kstroul_from_user. This makes it easier to read and less error prone. Signed-off-by: Peter Huewe Link: http://lkml.kernel.org/r/1307476707-14762-1-git-send-email-peterhuewe@gmx.de Signed-off-by: Steven Rostedt

tracing: Use NUMA allocation for per-cpu ring buffer pages

2011-06-15T02:04:39Z

The tracing ring buffer is a group of per-cpu ring buffers where allocation and logging is done on a per-cpu basis. The events that are generated on a particular CPU are logged in the corresponding buffer. This is to provide wait-free writes between CPUs and good NUMA node locality while accessing the ring buffer. However, the allocation routines consider NUMA locality only for buffer page metadata and not for the actual buffer page. This causes the pages to be allocated on the NUMA node local to the CPU where the allocation routine is running at the time. This patch fixes the problem by using a NUMA node specific allocation routine so that the pages are allocated from a NUMA node local to the logging CPU. I tested with the getuid_microbench from autotest. It is a simple binary that calls getuid() in a loop and measures the average time for the syscall to complete. The following command was used to test: $ getuid_microbench 1000000 Compared the numbers found on kernel with and without this patch and found that logging latency decreases by 30-50 ns/call. tracing with non-NUMA allocation - 569 ns/call tracing with NUMA allocation - 512 ns/call Signed-off-by: Vaibhav Nagarnaik Cc: Frederic Weisbecker Cc: Ingo Molnar Cc: Michael Rubin Cc: David Sharp Link: http://lkml.kernel.org/r/1304470602-20366-1-git-send-email-vnagarnaik@google.com Signed-off-by: Steven Rostedt

ftrace: Add internal recursive checks

2011-05-26T02:13:49Z

Witold reported a reboot caused by the selftests of the dynamic function tracer. He sent me a config and I used ktest to do a config_bisect on it (as my config did not cause the crash). It pointed out that the problem config was CONFIG_PROVE_RCU. What happened was that if multiple callbacks are attached to the function tracer, we iterate a list of callbacks. Because the list is managed by synchronize_sched() and preempt_disable, the access to the pointers uses rcu_dereference_raw(). When PROVE_RCU is enabled, the rcu_dereference_raw() calls some debugging functions, which happen to be traced. The tracing of the debug function would then call rcu_dereference_raw() which would then call the debug function and then... well you get the idea. I first wrote two different patches to solve this bug. 1) add a __rcu_dereference_raw() that would not do any checks. 2) add notrace to the offending debug functions. Both of these patches worked. Talking with Paul McKenney on IRC, he suggested to add recursion detection instead. This seemed to be a better solution, so I decided to implement it. As the task_struct already has a trace_recursion to detect recursion in the ring buffer, and that has a very small number it allows, I decided to use that same variable to add flags that can detect the recursion inside the infrastructure of the function tracer. I plan to change it so that the task struct bit can be checked in mcount, but as that requires changes to all archs, I will hold that off to the next merge window. Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Frederic Weisbecker Cc: Paul E. McKenney Link: http://lkml.kernel.org/r/1306348063.1465.116.camel@gandalf.stny.rr.com Reported-by: Witold Baryluk Signed-off-by: Steven Rostedt