Messages in this thread | | | Date | Wed, 1 Dec 2021 11:14:59 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH V2] cgroup: Trace event cgroup id fields should be u64 |
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On Wed, 1 Dec 2021 09:07:46 -0700 William Kucharski <william.kucharski@oracle.com> wrote:
> Various trace event fields that store cgroup IDs were declared as > ints, but cgroup_id(() returns a u64 and the structures and associated > TP_printk() calls were not updated to reflect this. > > Fixes: 743210386c03 ("cgroup: use cgrp->kn->id as the cgroup ID") > Signed-off-by: William Kucharski <william.kucharski@oracle.com> > --- > V2: Do not remove spaces from macro arguments > > include/trace/events/cgroup.h | 12 ++++++------ > 1 file changed, 6 insertions(+), 6 deletions(-) > > diff --git a/include/trace/events/cgroup.h b/include/trace/events/cgroup.h > index 7f42a3de59e6..1b68c842ac46 100644 > --- a/include/trace/events/cgroup.h > +++ b/include/trace/events/cgroup.h > @@ -59,7 +59,7 @@ DECLARE_EVENT_CLASS(cgroup, > > TP_STRUCT__entry( > __field( int, root ) > - __field( int, id ) > + __field( u64, id ) > __field( int, level )
It's best to move them around to prevent holes. This is not a packed structure, and the above will create a structure on the ring buffer that looks like:
int root; u64 id; int level; short path_offset; short path_size;
(the string() macro is a 4 byte word where the half is the offset of the actual string and the other half is the size of the string).
Having a 8 byte word between two 4 byte words, will add a 4 byte padding after the first 4 byte word (before the 8 byte word), and waste space on the ring buffer.
Better to move it around to be:
TP_STRUCT__entry( __field( int, root ) __field( int, level ) __field( u64, id )
That way the two 4 byte words will be together followed directly by the 8 byte word.
> __string( path, path ) > ), > @@ -71,7 +71,7 @@ DECLARE_EVENT_CLASS(cgroup, > __assign_str(path, path); > ), > > - TP_printk("root=%d id=%d level=%d path=%s", > + TP_printk("root=%d id=%llu level=%d path=%s", > __entry->root, __entry->id, __entry->level, __get_str(path)) > ); > > @@ -126,7 +126,7 @@ DECLARE_EVENT_CLASS(cgroup_migrate, > > TP_STRUCT__entry( > __field( int, dst_root ) > - __field( int, dst_id ) > + __field( u64, dst_id )
Same here. Just move dst_level above dst_id.
> __field( int, dst_level ) > __field( int, pid ) > __string( dst_path, path ) > @@ -142,7 +142,7 @@ DECLARE_EVENT_CLASS(cgroup_migrate, > __assign_str(comm, task->comm); > ), > > - TP_printk("dst_root=%d dst_id=%d dst_level=%d dst_path=%s pid=%d comm=%s", > + TP_printk("dst_root=%d dst_id=%llu dst_level=%d dst_path=%s pid=%d comm=%s", > __entry->dst_root, __entry->dst_id, __entry->dst_level, > __get_str(dst_path), __entry->pid, __get_str(comm)) > ); > @@ -171,7 +171,7 @@ DECLARE_EVENT_CLASS(cgroup_event, > > TP_STRUCT__entry( > __field( int, root ) > - __field( int, id ) > + __field( u64, id )
And here.
> __field( int, level ) > __string( path, path ) > __field( int, val ) > @@ -185,7 +185,7 @@ DECLARE_EVENT_CLASS(cgroup_event, > __entry->val = val; > ), > > - TP_printk("root=%d id=%d level=%d path=%s val=%d", > + TP_printk("root=%d id=%llu level=%d path=%s val=%d", > __entry->root, __entry->id, __entry->level, __get_str(path), > __entry->val) > );
-- Steve
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