Hi Daniel, On Wed, 15 Jan 2025 17:29:34 +0100 Daniel Wagner <dwag...@suse.de> wrote:
> On Wed, Jan 15, 2025 at 10:17:15AM -0500, Steven Rostedt wrote: > > [ Adding Masami ] > > Is it consistently the same locations being dropped? > > Yes, it is very consistent. > > > There's been cases of a compiler inlining some functions for the code > > called in the same file. If that happened, then those will likely be > > dropped. That can be tested by adding: > > > > bool noinline nvme_change_ctrl_state(struct nvme_ctrl *ctrl, > > enum nvme_ctrl_state new_state) > > > > You would think it shouldn't inline it, but there's nothing in the spec > > that says it can't do so. > > This did the trick, now I see the missing state transitions. Have you tried to use `perf probe`? Even if it is inlined, you can find them by perf probe -a nvme_change_ctrl_state new_state But perhaps, some of them are inlined with constant numbers (maybe you can find them as nvme_change_ctrl_state.constprop.XXX in kallsyms) If my guess is correct, it is not inlined but the constant propagation optimization[1] has been done by the compiler. [1] https://en.wikipedia.org/wiki/Constant_folding#Constant_propagation IIRC, commit 66f69b219716 ("perf probe: Support DW_AT_const_value constant value") should support this case. Thank you, > > > > The system is idle, so I hope it's not just a dropped event. Any ideas > > > what I am doing wrong? > > > > I don't think it's a dropped event. It's not busy enough. But the compiler > > making a copy of the function (by inlining or what not) can cause something > > like this to happen. > > I didn't expect that the compiler does inlining and not inlining at the > same time. Again what learned :) > > Thanks, > Daniel -- Masami Hiramatsu (Google) <mhira...@kernel.org>
