Peter, can you take a look at these patches please. I believe you're the only one that really maintains this code today.
-- Steve On Mon, 08 Sep 2025 13:14:12 -0400 Steven Rostedt <rost...@kernel.org> wrote: > [ > This is simply a resend of version 15 of this patch series > but with only the kernel changes. I'm separating out the user space > changes to their own series. > The original v15 is here: > > https://lore.kernel.org/linux-trace-kernel/20250825180638.877627...@kernel.org/ > ] > > This patch set is based off of perf/core of the tip tree: > git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git > > To run this series, you can checkout this repo that has this series as well > as the above: > > git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace.git > unwind/perf-test > > This series implements the perf interface to use deferred user space stack > tracing. > > Patch 1 adds a new API interface to the user unwinder logic to allow perf to > get the current context cookie for it's task event tracing. Perf's task event > tracing maps a single task per perf event buffer and it follows the task > around, so it only needs to implement its own task_work to do the deferred > stack trace. Because it can still suffer not knowing which user stack trace > belongs to which kernel stack due to dropped events, having the cookie to > create a unique identifier for each user space stack trace to know which > kernel stack to append it to is useful. > > Patch 2 adds the per task deferred stack traces to perf. It adds a new event > type called PERF_RECORD_CALLCHAIN_DEFERRED that is recorded when a task is > about to go back to user space and happens in a location that pages may be > faulted in. It also adds a new callchain context called > PERF_CONTEXT_USER_DEFERRED > that is used as a place holder in a kernel callchain to append the deferred > user space stack trace to. > > Patch 3 adds the user stack trace context cookie in the kernel callchain right > after the PERF_CONTEXT_USER_DEFERRED context so that the user space side can > map the request to the deferred user space stack trace. > > Patch 4 adds support for the per CPU perf events that will allow the kernel to > associate each of the per CPU perf event buffers to a single application. This > is needed so that when a request for a deferred stack trace happens on a task > that then migrates to another CPU, it will know which CPU buffer to use to > record the stack trace on. It is possible to have more than one perf user tool > running and a request made by one perf tool should have the deferred trace go > to the same perf tool's perf CPU event buffer. A global list of all the > descriptors representing each perf tool that is using deferred stack tracing > is created to manage this. > > > Josh Poimboeuf (1): > perf: Support deferred user callchains > > Steven Rostedt (3): > unwind deferred: Add unwind_user_get_cookie() API > perf: Have the deferred request record the user context cookie > perf: Support deferred user callchains for per CPU events > > ---- > include/linux/perf_event.h | 11 +- > include/linux/unwind_deferred.h | 5 + > include/uapi/linux/perf_event.h | 25 +- > kernel/bpf/stackmap.c | 4 +- > kernel/events/callchain.c | 14 +- > kernel/events/core.c | 421 > +++++++++++++++++++++++++++++++++- > kernel/unwind/deferred.c | 21 ++ > tools/include/uapi/linux/perf_event.h | 25 +- > 8 files changed, 518 insertions(+), 8 deletions(-)
