Re: [PATCH v7 3/3] mm: vmscan: add PIDs to vmscan tracepoints

[Masami Hiramatsu (Google) <mhiramat@kernel.org>]

Hi,

On Mon, 23 Feb 2026 09:15:44 -0800
Thomas Ballasi <tballasi@linux.microsoft.com> wrote:

> The changes aims at adding additionnal tracepoints variables to help
> debuggers attribute them to specific processes.
> 
> The PID field uses in_task() to reliably detect when we're in process
> context and can safely access current->pid.  When not in process
> context (such as in interrupt or in an asynchronous RCU context), the
> field is set to -1 as a sentinel value.
> 
> Signed-off-by: Thomas Ballasi <tballasi@linux.microsoft.com>
> ---
>  include/trace/events/vmscan.h | 34 +++++++++++++++++++++++++---------
>  1 file changed, 25 insertions(+), 9 deletions(-)
> 
> diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
> index 1212f6a7c223e..15b31281f0955 100644
> --- a/include/trace/events/vmscan.h
> +++ b/include/trace/events/vmscan.h
> @@ -122,18 +122,22 @@ DECLARE_EVENT_CLASS(mm_vmscan_direct_reclaim_begin_template,
>  		__field(	unsigned long,	gfp_flags	)
>  		__field(	u64,	memcg_id	)
>  		__field(	int,	order		)
> +		__field(	int,	pid		)
>  	),
>  
>  	TP_fast_assign(
>  		__entry->gfp_flags	= (__force unsigned long)gfp_flags;
>  		__entry->order		= order;
> +		__entry->pid		= current->pid;

All entries saves current->pid in common_pid field. Can you use
this common field?

# cat events/vmscan/mm_vmscan_reclaim_pages/format 
name: mm_vmscan_reclaim_pages
ID: 590
format:
	field:unsigned short common_type;	offset:0;	size:2;	signed:0;
	field:unsigned char common_flags;	offset:2;	size:1;	signed:0;
	field:unsigned char common_preempt_count;	offset:3;	size:1;	signed:0;
	field:int common_pid;	offset:4;	size:4;	signed:1;    ## <------------here

	field:int nid;	offset:8;	size:4;	signed:1;
	field:unsigned long nr_scanned;	offset:16;	size:8;	signed:0;
	field:unsigned long nr_reclaimed;	offset:24;	size:8;	signed:0;
	field:unsigned long nr_dirty;	offset:32;	size:8;	signed:0;
	field:unsigned long nr_writeback;	offset:40;	size:8;	signed:0;
	field:unsigned long nr_congested;	offset:48;	size:8;	signed:0;
	field:unsigned long nr_immediate;	offset:56;	size:8;	signed:0;
	field:unsigned int nr_activate0;	offset:64;	size:4;	signed:0;
	field:unsigned int nr_activate1;	offset:68;	size:4;	signed:0;
	field:unsigned long nr_ref_keep;	offset:72;	size:8;	signed:0;
	field:unsigned long nr_unmap_fail;	offset:80;	size:8;	signed:0;

Thank you,

-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>