Peter, It's been over 3 weeks since the original has been sent. And last week I broke it up to only hold the kernel changes. Can you please take a look at it?
I have updated the user space side with Namhyung Kim's updates: https://lore.kernel.org/all/[email protected]/ Also, the two patches to enable deferred unwinding in x86 has been ignored for almost three weeks as well: https://lore.kernel.org/linux-trace-kernel/[email protected]/ -- Steve On Mon, 8 Sep 2025 13:21:06 -0400 Steven Rostedt <[email protected]> wrote: > 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 <[email protected]> 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/[email protected]/ > > ] > > > > 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(-) >
