ring-buffer: Fix bytes info in per_cpu buffer stats
commit 45d99ea4 upstream. The 'bytes' info in file 'per_cpu/cpu<X>/stats' means the number of bytes in cpu buffer that have not been consumed. However, currently after consuming data by reading file 'trace_pipe', the 'bytes' info was not changed as expected. # cat per_cpu/cpu0/stats entries: 0 overrun: 0 commit overrun: 0 bytes: 568 <--- 'bytes' is problematical !!! oldest event ts: 8651.371479 now ts: 8653.912224 dropped events: 0 read events: 8 The root cause is incorrect stat on cpu_buffer->read_bytes. To fix it: 1. When stat 'read_bytes', account consumed event in rb_advance_reader(); 2. When stat 'entries_bytes', exclude the discarded padding event which is smaller than minimum size because it is invisible to reader. Then use rb_page_commit() instead of BUF_PAGE_SIZE at where accounting for page-based read/remove/overrun. Also correct the comments of ring_buffer_bytes_cpu() in this patch. Link: https://lore.kernel.org/linux-trace-kernel/20230921125425.1708423-1-zhengyejian1@huawei.com Cc: stable@vger.kernel.org Fixes: c64e148a ("trace: Add ring buffer stats to measure rate of events") Signed-off-by:Zheng Yejian <zhengyejian1@huawei.com> Signed-off-by:
Steven Rostedt (Google) <rostedt@goodmis.org> Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
parent
8067b844
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