On Fri, 3 Feb 2017 23:26:46 +0900 Namhyung Kim <[email protected]> wrote:
> Hi Steve, > > On Fri, Feb 3, 2017 at 10:40 PM, Steven Rostedt <[email protected]> wrote: > > From: "Steven Rostedt (VMware)" <[email protected]> > > > > This is a micro-optimization, but as it has to deal with a fast path of the > > function tracer, these optimizations can be noticed. > > > > The ftrace_lookup_ip() returns true if the given ip is found in the hash. If > > it's not found or the hash is NULL, it returns false. But there's some cases > > that a NULL hash is a true, and the ftrace_hash_empty() is tested before > > calling ftrace_lookup_ip() in those cases. But as ftrace_lookup_ip() tests > > that first, that adds a few extra unneeded instructions in those cases. > > > > A new static "always_inlined" function is created that does not perform the > > hash empty test. This most only be used by callers that do the check first > > anyway, as an empty or NULL hash could cause a crash if a lookup is > > performed on it. > > > > Also add kernel doc for the ftrace_lookup_ip() main function. > > It'd be nice if ftrace_graph_addr() was changed also. > Yeah, I was looking at that. But I was nervous about placing this function in the header file. -- Steve
