Messages in this thread | | | Date | Fri, 6 Aug 2021 13:51:24 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH] trace: Add migrate-disabled counter to tracing output. |
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On Fri, 6 Aug 2021 18:49:07 +0200 Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote:
> From: Thomas Gleixner <tglx@linutronix.de> > > migrate_disable() forbids task migration to another CPU. It is available > since v5.11 and has already users such as highmem or BPF. It is useful > to observe this task state in tracing which already has other states > like the preemption counter. > > Add the migrate-disable counter to the trace entry so it shows up in the > trace. Due to the users mentioned above, it is already possible to > observe it: > > | bash-1108 [000] ...21 73.950578: rss_stat: mm_id=2213312838 curr=0 type=MM_ANONPAGES size=8192B > | bash-1108 [000] d..31 73.951222: irq_disable: caller=flush_tlb_mm_range+0x115/0x130 parent=ptep_clear_flush+0x42/0x50 > | bash-1108 [000] d..31 73.951222: tlb_flush: pages:1 reason:local mm shootdown (3) > > The last value is the migrate-disable counter. > > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > [bigeasy: patch description.] > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> > --- > include/linux/trace_events.h | 2 ++ > kernel/trace/trace.c | 26 +++++++++++++++++++------- > kernel/trace/trace_events.c | 1 + > kernel/trace/trace_output.c | 5 +++++ > 4 files changed, 27 insertions(+), 7 deletions(-) > > diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h > index ad413b382a3ca..7c4280b4c6be7 100644 > --- a/include/linux/trace_events.h > +++ b/include/linux/trace_events.h > @@ -69,6 +69,7 @@ struct trace_entry { > unsigned char flags; > unsigned char preempt_count; > int pid; > + unsigned char migrate_disable;
The only issue I have with this patch is this part. It extends the header of all events beyond 8 bytes, and actually adds another 4 or 8 bytes despite being just a char in size. That's because this is a header of a structure, which depending on the first field of an event, padding may be added to have 4 or 8 byte alignment.
I'll be fine with merging this counter with either flags or preempt_count (neither needs all 8 bits). I can figure out how to update libtraceevent to handle this case.
-- Steve
> }; > > #define TRACE_EVENT_TYPE_MAX \ > @@ -157,6 +158,7 @@ static inline void tracing_generic_entry_update(struct trace_entry *entry, > unsigned int trace_ctx)
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