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 <[email protected]>
---
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 )
__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 )
__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 )
__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)
);
--
2.33.1
On Wed, 1 Dec 2021 09:07:46 -0700
William Kucharski <[email protected]> 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 <[email protected]>
> ---
> 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
I had pondered that as a consequence for two of the three uses but wasn't sure
if it was worth reordering things; I can easily do so.
What do you suggest for cgroup_migrate as that will have a hole either way
as it's:
TP_STRUCT__entry(
__field( int, dst_root )
__field( u64, dst_id )
__field( int, dst_level )
__field( int, pid )
__string( dst_path, path )
__string( comm, task->comm )
),
if I put dst_level above dst_id, the int for pid field will leave a hole
anyway because the string pointer for dst_path will want to be 64-bit
aligned.
Thanks in advance.
> On Dec 1, 2021, at 9:14 AM, Steven Rostedt <[email protected]> wrote:
>
> On Wed, 1 Dec 2021 09:07:46 -0700
> William Kucharski <[email protected]> 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 <[email protected]>
>> ---
>> 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
On Wed, 1 Dec 2021 16:27:54 +0000
William Kucharski <[email protected]> wrote:
> I had pondered that as a consequence for two of the three uses but wasn't sure
> if it was worth reordering things; I can easily do so.
>
> What do you suggest for cgroup_migrate as that will have a hole either way
> as it's:
>
> TP_STRUCT__entry(
> __field( int, dst_root )
> __field( u64, dst_id )
> __field( int, dst_level )
> __field( int, pid )
> __string( dst_path, path )
> __string( comm, task->comm )
> ),
>
> if I put dst_level above dst_id, the int for pid field will leave a hole
> anyway because the string pointer for dst_path will want to be 64-bit
> aligned.
>
> Thanks in advance.
>
It's not actually a string pointer, both string() macros are really 4 byte
words. The above would be best compressed as:
TP_STRUCT__entry(
__field( int, dst_root )
__field( int, dst_level )
__field( u64, dst_id )
__field( int, pid )
__string( dst_path, path )
__string( comm, task->comm )
),
What that would turn into is:
struct __entry {
int dst_root;
int dst_level;
u64 dst_id;
int pid;
int dst_path_offset_size;
int comm_offset_size;
char strings[];
}
Remember, this is used for storing data onto the ring buffer. I'll make up
two strings to show an example.
dst_path = "/path/to/dst_path";
comm = "bash";
The string(dst_path) and string(comm) would be where the data to find the
strings are. The strings will be stored in the strings[] field of the
structure, and the dst_path and comm fields will be used to find those
strings.
dst_root = 1;
dst_level = 2;
dst_id = 3;
pid = 4;
dst_path = (28 << 16) | 18;
comm = ((28 + 18) << 16 | 5;
strings = "/path/to/dst_path\0bash\0";
The dst_path holds how to find the string it represents. It starts at
offset 28[*] (sizeof(int) * 5 + sizeof(u64))
And has size of 18 (strlen("/path/to/dst_path") + 1)
The comm string starts at offset 46 (28 + size of dst_path), and has he
size of 5 (strlen("bash") + 1).
So consider "string()" macros to be only 4 bytes in size. And leave the
"holes" at the end, especially if there's strings, because the will start
the actual strings nicely aligned.
-- Steve
[*] It really starts at a later offset, because there's common fields added
before the first field (common_type, common_flags, common_preempt_count,
common_pid) that is also included in that offset count.