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| author |   Steven Rostedt (VMware) <rostedt@goodmis.org> | 2021-06-09 18:04:58 -0400 |
|---|---|---|
| committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2021-06-10 13:42:03 -0400 |
| commit | faa76a6c289f43c88affcb292bc02870921d93bf (patch) | |
| tree | 48605cec7494363fa92500802a9ae2f474d94641 /kernel | |
| parent | bootconfig: Share the checksum function with tools (diff) | |
| download | linux-dev-faa76a6c289f43c88affcb292bc02870921d93bf.tar.xz linux-dev-faa76a6c289f43c88affcb292bc02870921d93bf.zip | |
tracing: Simplify the max length test when using the filtering temp buffer
When filtering trace events, a temp buffer is used because the extra copy
from the temp buffer into the ring buffer is still faster than the direct
write into the ring buffer followed by a discard if the filter does not
match.
But the data that can be stored in the temp buffer is a PAGE_SIZE minus the
ring buffer event header. The calculation of that header size is complex,
but using the helper macro "struct_size()" can simplify it.
Link: https://lore.kernel.org/stable/CAHk-=whKbJkuVmzb0hD3N6q7veprUrSpiBHRxVY=AffWZPtxmg@mail.gmail.com/
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/trace/trace.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 2e592885a167..a0a84ff46ecd 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2735,8 +2735,10 @@ trace_event_buffer_lock_reserve(struct trace_buffer **current_rb, (trace_file->flags & (EVENT_FILE_FL_SOFT_DISABLED | EVENT_FILE_FL_FILTERED)) && (entry = this_cpu_read(trace_buffered_event))) { /* Try to use the per cpu buffer first */ + int max_len = PAGE_SIZE - struct_size(entry, array, 1); + val = this_cpu_inc_return(trace_buffered_event_cnt); - if ((len < (PAGE_SIZE - sizeof(*entry) - sizeof(entry->array[0]))) && val == 1) { + if (val == 1 && likely(len <= max_len)) { trace_event_setup(entry, type, trace_ctx); entry->array[0] = len; return entry; |