Re: [PATCH perf-tools-next v8 1/6] perf ftrace: Optimise __cmd_ftrace() stack frame with strbuf streaming

[sashiko-bot@kernel.org]

> In __cmd_ftrace(), incoming trace data from trace_pipe was historically
> buffered in a fixed 4096-byte array allocated directly on the stack
> frame. Furthermore, reads were written directly to stdout via fwrite()
> in arbitrary chunk sizes, rather than as discrete, well-delimited
> trace lines.
> 
> Refactor __cmd_ftrace() to employ dynamic heap allocation for the read
> buffer alongside a dynamic struct strbuf to accumulate streamed
> characters into whole lines. Pre-allocating the strbuf ensures that
> line processing incurs zero heap reallocations during steady-state
> polling, while the stack frame of __cmd_ftrace() is reduced by over 96%
> (down to ~160 bytes). Robust error and EOF detection on stdout and the
> trace stream ensures polling terminates cleanly upon pipeline or pager
> exit, while retrying on non-fatal EAGAIN and EINTR conditions prevents
> premature termination on non-blocking reads or signal interruptions.
> 
> Signed-off-by: Aaron Tomlin <atomlin@atomlin.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261018023753.584873-1-atomlin@atomlin.com?part=1