Hi,
On 2/11/24 10:07 PM, Samuel Thibault wrote:
> Damien Zammit, le dim. 11 févr. 2024 10:55:26 +0000, a ecrit:
>>>> diff --git a/kern/task.h b/kern/task.h
>>>> index dec3a530..27970620 100644
>>>> --- a/kern/task.h
>>>> +++ b/kern/task.h
>>>> @@ -61,11 +61,11 @@ struct task {
>>>> decl_simple_lock_data(,lock) /* Task's lock */
>>>> int ref_count; /* Number of references to me */
>>>>
>>>> - /* Flags */
>>>> - unsigned int active:1, /* Task has not been terminated */
>>>> - /* boolean_t */ may_assign:1, /* can assigned pset be changed? */
>>>> - assign_active:1, /* waiting for may_assign */
>>>> - essential:1; /* Is this task essential for the
>>>> system? */
>>>> + /* Addressable flags */
>>>> + unsigned char active; /* Task has not been terminated */
>>>> + unsigned char may_assign; /* can assigned pset be changed? */
>>>> + unsigned char assign_active; /* waiting for may_assign */
>>>> + unsigned char essential; /* Is this task essential for the
>>>> system? */
>>> AIUI only assign_active need to be adressable? Better make only that one
>>> addressable.
>> Looking at the existing flag types, it needs to fit into part of a cacheline.
> Why would it need to fit in a cacheline?
See comment above struct task:
/*
* Task name buffer size. The size is chosen so that struct task fits
* into three cache lines. The size of a cache line on a typical CPU
* is 64 bytes.
*/
#define TASK_NAME_SIZE 32
>> The way I have done it, I rearranged the existing 4 byte integer to be 4
>> separate single byte flags.
>> If you want me to put only one of the values into an addressable field,
>> how will I retain the same size for the rest of the fields?
> What do you mean by "the same size"?
I think the actual sizeof(struct task) and its layout matters.
Therefore, my original code change here preserves most of the layout and
sizeof(struct task).
Damien
