diff options
author | Linus Torvalds | 2024-01-18 14:35:29 -0800 |
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committer | Linus Torvalds | 2024-01-18 14:35:29 -0800 |
commit | a2ded784cd7fd83e567829637068cd86aeffbeaf (patch) | |
tree | 9924ca8854858fc5558e59b136d1f32695bc8cc4 /Documentation | |
parent | 5b890ad456b16a5b45e7f86d9708d7248e73d0f8 (diff) | |
parent | 25742aeb135c4a44e92fb347e037adaa145b9484 (diff) |
Merge tag 'trace-v6.8' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
Pull tracing updates from Steven Rostedt:
- Allow kernel trace instance creation to specify what events are
created
Inside the kernel, a subsystem may create a tracing instance that it
can use to send events to user space. This sub-system may not care
about the thousands of events that exist in eventfs. Allow the
sub-system to specify what sub-systems of events it cares about, and
only those events are exposed to this instance.
- Allow the ring buffer to be broken up into bigger sub-buffers than
just the architecture page size.
A new tracefs file called "buffer_subbuf_size_kb" is created. The
user can now specify a minimum size the sub-buffer may be in
kilobytes. Note, that the implementation currently make the
sub-buffer size a power of 2 pages (1, 2, 4, 8, 16, ...) but the user
only writes in kilobyte size, and the sub-buffer will be updated to
the next size that it will can accommodate it. If the user writes in
10, it will change the size to be 4 pages on x86 (16K), as that is
the next available size that can hold 10K pages.
- Update the debug output when a corrupt time is detected in the ring
buffer. If the ring buffer detects inconsistent timestamps, there's a
debug config options that will dump the contents of the meta data of
the sub-buffer that is used for debugging. Add some more information
to this dump that helps with debugging.
- Add more timestamp debugging checks (only triggers when the config is
enabled)
- Increase the trace_seq iterator to 2 page sizes.
- Allow strings written into tracefs_marker to be larger. Up to just
under 2 page sizes (based on what trace_seq can hold).
- Increase the trace_maker_raw write to be as big as a sub-buffer can
hold.
- Remove 32 bit time stamp logic, now that the rb_time_cmpxchg() has
been removed.
- More selftests were added.
- Some code clean ups as well.
* tag 'trace-v6.8' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (29 commits)
ring-buffer: Remove stale comment from ring_buffer_size()
tracing histograms: Simplify parse_actions() function
tracing/selftests: Remove exec permissions from trace_marker.tc test
ring-buffer: Use subbuf_order for buffer page masking
tracing: Update subbuffer with kilobytes not page order
ringbuffer/selftest: Add basic selftest to test changing subbuf order
ring-buffer: Add documentation on the buffer_subbuf_order file
ring-buffer: Just update the subbuffers when changing their allocation order
ring-buffer: Keep the same size when updating the order
tracing: Stop the tracing while changing the ring buffer subbuf size
tracing: Update snapshot order along with main buffer order
ring-buffer: Make sure the spare sub buffer used for reads has same size
ring-buffer: Do no swap cpu buffers if order is different
ring-buffer: Clear pages on error in ring_buffer_subbuf_order_set() failure
ring-buffer: Read and write to ring buffers with custom sub buffer size
ring-buffer: Set new size of the ring buffer sub page
ring-buffer: Add interface for configuring trace sub buffer size
ring-buffer: Page size per ring buffer
ring-buffer: Have ring_buffer_print_page_header() be able to access ring_buffer_iter
ring-buffer: Check if absolute timestamp goes backwards
...
Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/trace/ftrace.rst | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst index 16122a8895ba..7e7b8ec17934 100644 --- a/Documentation/trace/ftrace.rst +++ b/Documentation/trace/ftrace.rst @@ -218,6 +218,27 @@ of ftrace. Here is a list of some of the key files: This displays the total combined size of all the trace buffers. + buffer_subbuf_size_kb: + + This sets or displays the sub buffer size. The ring buffer is broken up + into several same size "sub buffers". An event can not be bigger than + the size of the sub buffer. Normally, the sub buffer is the size of the + architecture's page (4K on x86). The sub buffer also contains meta data + at the start which also limits the size of an event. That means when + the sub buffer is a page size, no event can be larger than the page + size minus the sub buffer meta data. + + Note, the buffer_subbuf_size_kb is a way for the user to specify the + minimum size of the subbuffer. The kernel may make it bigger due to the + implementation details, or simply fail the operation if the kernel can + not handle the request. + + Changing the sub buffer size allows for events to be larger than the + page size. + + Note: When changing the sub-buffer size, tracing is stopped and any + data in the ring buffer and the snapshot buffer will be discarded. + free_buffer: If a process is performing tracing, and the ring buffer should be |