* [PATCH] sched_ext: Use BTF_ID to resolve task_struct
@ 2024-10-16 2:41 Tianchen Ding
2024-10-16 16:57 ` Alexei Starovoitov
0 siblings, 1 reply; 4+ messages in thread
From: Tianchen Ding @ 2024-10-16 2:41 UTC (permalink / raw)
To: linux-kernel; +Cc: Tejun Heo, David Vernet, Peter Zijlstra, bpf
Save the searching time during bpf_scx_init.
Signed-off-by: Tianchen Ding <dtcccc@linux.alibaba.com>
---
kernel/sched/ext.c | 12 +++---------
1 file changed, 3 insertions(+), 9 deletions(-)
diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 609b9fb00d6f..1d11a96eefb8 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -5343,7 +5343,7 @@ static int scx_ops_enable(struct sched_ext_ops *ops, struct bpf_link *link)
extern struct btf *btf_vmlinux;
static const struct btf_type *task_struct_type;
-static u32 task_struct_type_id;
+BTF_ID_LIST_SINGLE(task_struct_btf_ids, struct, task_struct);
static bool set_arg_maybe_null(const char *op, int arg_n, int off, int size,
enum bpf_access_type type,
@@ -5395,7 +5395,7 @@ static bool set_arg_maybe_null(const char *op, int arg_n, int off, int size,
*/
info->reg_type = PTR_MAYBE_NULL | PTR_TO_BTF_ID | PTR_TRUSTED;
info->btf = btf_vmlinux;
- info->btf_id = task_struct_type_id;
+ info->btf_id = task_struct_btf_ids[0];
return true;
}
@@ -5547,13 +5547,7 @@ static void bpf_scx_unreg(void *kdata, struct bpf_link *link)
static int bpf_scx_init(struct btf *btf)
{
- s32 type_id;
-
- type_id = btf_find_by_name_kind(btf, "task_struct", BTF_KIND_STRUCT);
- if (type_id < 0)
- return -EINVAL;
- task_struct_type = btf_type_by_id(btf, type_id);
- task_struct_type_id = type_id;
+ task_struct_type = btf_type_by_id(btf, task_struct_btf_ids[0]);
return 0;
}
--
2.39.3
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] sched_ext: Use BTF_ID to resolve task_struct
2024-10-16 2:41 [PATCH] sched_ext: Use BTF_ID to resolve task_struct Tianchen Ding
@ 2024-10-16 16:57 ` Alexei Starovoitov
2024-10-17 1:57 ` Tianchen Ding
0 siblings, 1 reply; 4+ messages in thread
From: Alexei Starovoitov @ 2024-10-16 16:57 UTC (permalink / raw)
To: Tianchen Ding; +Cc: LKML, Tejun Heo, David Vernet, Peter Zijlstra, bpf
On Tue, Oct 15, 2024 at 7:42 PM Tianchen Ding <dtcccc@linux.alibaba.com> wrote:
>
> Save the searching time during bpf_scx_init.
>
> Signed-off-by: Tianchen Ding <dtcccc@linux.alibaba.com>
> ---
> kernel/sched/ext.c | 12 +++---------
> 1 file changed, 3 insertions(+), 9 deletions(-)
>
> diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
> index 609b9fb00d6f..1d11a96eefb8 100644
> --- a/kernel/sched/ext.c
> +++ b/kernel/sched/ext.c
> @@ -5343,7 +5343,7 @@ static int scx_ops_enable(struct sched_ext_ops *ops, struct bpf_link *link)
>
> extern struct btf *btf_vmlinux;
> static const struct btf_type *task_struct_type;
> -static u32 task_struct_type_id;
> +BTF_ID_LIST_SINGLE(task_struct_btf_ids, struct, task_struct);
>
> static bool set_arg_maybe_null(const char *op, int arg_n, int off, int size,
> enum bpf_access_type type,
> @@ -5395,7 +5395,7 @@ static bool set_arg_maybe_null(const char *op, int arg_n, int off, int size,
> */
> info->reg_type = PTR_MAYBE_NULL | PTR_TO_BTF_ID | PTR_TRUSTED;
> info->btf = btf_vmlinux;
> - info->btf_id = task_struct_type_id;
> + info->btf_id = task_struct_btf_ids[0];
>
> return true;
> }
> @@ -5547,13 +5547,7 @@ static void bpf_scx_unreg(void *kdata, struct bpf_link *link)
>
> static int bpf_scx_init(struct btf *btf)
> {
> - s32 type_id;
> -
> - type_id = btf_find_by_name_kind(btf, "task_struct", BTF_KIND_STRUCT);
> - if (type_id < 0)
> - return -EINVAL;
> - task_struct_type = btf_type_by_id(btf, type_id);
> - task_struct_type_id = type_id;
> + task_struct_type = btf_type_by_id(btf, task_struct_btf_ids[0]);
Good optimization, but it's also unnecessary.
btf_id is already in btf_tracing_ids[BTF_TRACING_TYPE_TASK].
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] sched_ext: Use BTF_ID to resolve task_struct
2024-10-16 16:57 ` Alexei Starovoitov
@ 2024-10-17 1:57 ` Tianchen Ding
2024-10-17 2:12 ` Alexei Starovoitov
0 siblings, 1 reply; 4+ messages in thread
From: Tianchen Ding @ 2024-10-17 1:57 UTC (permalink / raw)
To: Alexei Starovoitov; +Cc: LKML, Tejun Heo, David Vernet, Peter Zijlstra, bpf
On 2024/10/17 00:57, Alexei Starovoitov wrote:
> On Tue, Oct 15, 2024 at 7:42 PM Tianchen Ding <dtcccc@linux.alibaba.com> wrote:
>>
>> Save the searching time during bpf_scx_init.
>>
>> Signed-off-by: Tianchen Ding <dtcccc@linux.alibaba.com>
>> ---
>> kernel/sched/ext.c | 12 +++---------
>> 1 file changed, 3 insertions(+), 9 deletions(-)
>>
>> diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
>> index 609b9fb00d6f..1d11a96eefb8 100644
>> --- a/kernel/sched/ext.c
>> +++ b/kernel/sched/ext.c
>> @@ -5343,7 +5343,7 @@ static int scx_ops_enable(struct sched_ext_ops *ops, struct bpf_link *link)
>>
>> extern struct btf *btf_vmlinux;
>> static const struct btf_type *task_struct_type;
>> -static u32 task_struct_type_id;
>> +BTF_ID_LIST_SINGLE(task_struct_btf_ids, struct, task_struct);
>>
>> static bool set_arg_maybe_null(const char *op, int arg_n, int off, int size,
>> enum bpf_access_type type,
>> @@ -5395,7 +5395,7 @@ static bool set_arg_maybe_null(const char *op, int arg_n, int off, int size,
>> */
>> info->reg_type = PTR_MAYBE_NULL | PTR_TO_BTF_ID | PTR_TRUSTED;
>> info->btf = btf_vmlinux;
>> - info->btf_id = task_struct_type_id;
>> + info->btf_id = task_struct_btf_ids[0];
>>
>> return true;
>> }
>> @@ -5547,13 +5547,7 @@ static void bpf_scx_unreg(void *kdata, struct bpf_link *link)
>>
>> static int bpf_scx_init(struct btf *btf)
>> {
>> - s32 type_id;
>> -
>> - type_id = btf_find_by_name_kind(btf, "task_struct", BTF_KIND_STRUCT);
>> - if (type_id < 0)
>> - return -EINVAL;
>> - task_struct_type = btf_type_by_id(btf, type_id);
>> - task_struct_type_id = type_id;
>> + task_struct_type = btf_type_by_id(btf, task_struct_btf_ids[0]);
>
> Good optimization, but it's also unnecessary.
>
> btf_id is already in btf_tracing_ids[BTF_TRACING_TYPE_TASK].
Get it. Thanks!
BTW, do you think we should add a zero check for
btf_tracing_ids[BTF_TRACING_TYPE_TASK] here?
task_struct should always be valid. If something wrong, resolve_btfids will also
throw a warning. I'm not sure whether to add a sanity check here.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] sched_ext: Use BTF_ID to resolve task_struct
2024-10-17 1:57 ` Tianchen Ding
@ 2024-10-17 2:12 ` Alexei Starovoitov
0 siblings, 0 replies; 4+ messages in thread
From: Alexei Starovoitov @ 2024-10-17 2:12 UTC (permalink / raw)
To: Tianchen Ding; +Cc: LKML, Tejun Heo, David Vernet, Peter Zijlstra, bpf
On Wed, Oct 16, 2024 at 6:57 PM Tianchen Ding <dtcccc@linux.alibaba.com> wrote:
>
> On 2024/10/17 00:57, Alexei Starovoitov wrote:
> > On Tue, Oct 15, 2024 at 7:42 PM Tianchen Ding <dtcccc@linux.alibaba.com> wrote:
> >>
> >> Save the searching time during bpf_scx_init.
> >>
> >> Signed-off-by: Tianchen Ding <dtcccc@linux.alibaba.com>
> >> ---
> >> kernel/sched/ext.c | 12 +++---------
> >> 1 file changed, 3 insertions(+), 9 deletions(-)
> >>
> >> diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
> >> index 609b9fb00d6f..1d11a96eefb8 100644
> >> --- a/kernel/sched/ext.c
> >> +++ b/kernel/sched/ext.c
> >> @@ -5343,7 +5343,7 @@ static int scx_ops_enable(struct sched_ext_ops *ops, struct bpf_link *link)
> >>
> >> extern struct btf *btf_vmlinux;
> >> static const struct btf_type *task_struct_type;
> >> -static u32 task_struct_type_id;
> >> +BTF_ID_LIST_SINGLE(task_struct_btf_ids, struct, task_struct);
> >>
> >> static bool set_arg_maybe_null(const char *op, int arg_n, int off, int size,
> >> enum bpf_access_type type,
> >> @@ -5395,7 +5395,7 @@ static bool set_arg_maybe_null(const char *op, int arg_n, int off, int size,
> >> */
> >> info->reg_type = PTR_MAYBE_NULL | PTR_TO_BTF_ID | PTR_TRUSTED;
> >> info->btf = btf_vmlinux;
> >> - info->btf_id = task_struct_type_id;
> >> + info->btf_id = task_struct_btf_ids[0];
> >>
> >> return true;
> >> }
> >> @@ -5547,13 +5547,7 @@ static void bpf_scx_unreg(void *kdata, struct bpf_link *link)
> >>
> >> static int bpf_scx_init(struct btf *btf)
> >> {
> >> - s32 type_id;
> >> -
> >> - type_id = btf_find_by_name_kind(btf, "task_struct", BTF_KIND_STRUCT);
> >> - if (type_id < 0)
> >> - return -EINVAL;
> >> - task_struct_type = btf_type_by_id(btf, type_id);
> >> - task_struct_type_id = type_id;
> >> + task_struct_type = btf_type_by_id(btf, task_struct_btf_ids[0]);
> >
> > Good optimization, but it's also unnecessary.
> >
> > btf_id is already in btf_tracing_ids[BTF_TRACING_TYPE_TASK].
>
> Get it. Thanks!
>
> BTW, do you think we should add a zero check for
> btf_tracing_ids[BTF_TRACING_TYPE_TASK] here?
> task_struct should always be valid. If something wrong, resolve_btfids will also
> throw a warning. I'm not sure whether to add a sanity check here.
Definitely shouldn't add run-time checks.
Build check may work, but feels overkill at this point.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2024-10-16 2:41 [PATCH] sched_ext: Use BTF_ID to resolve task_struct Tianchen Ding
2024-10-16 16:57 ` Alexei Starovoitov
2024-10-17 1:57 ` Tianchen Ding
2024-10-17 2:12 ` Alexei Starovoitov
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