diff mbox series

[bpf,1/4] libbpf: Adjust ring buffer size when probing ring buffer map

Message ID 20221111092642.2333724-2-houtao@huaweicloud.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series libbpf: Fixes for ring buffer | expand

Checks

Context Check Description
netdev/tree_selection success Clearly marked for bpf
netdev/fixes_present success Fixes tag present in non-next series
netdev/subject_prefix success Link
netdev/cover_letter success Series has a cover letter
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/cc_maintainers success CCed 12 of 12 maintainers
netdev/build_clang success Errors and warnings before: 0 this patch: 0
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 0 this patch: 0
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 22 lines checked
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
bpf/vmtest-bpf-VM_Test-3 fail Logs for build for aarch64 with gcc
bpf/vmtest-bpf-VM_Test-4 fail Logs for build for aarch64 with llvm-16
bpf/vmtest-bpf-VM_Test-5 success Logs for build for s390x with gcc
bpf/vmtest-bpf-VM_Test-6 success Logs for build for x86_64 with gcc
bpf/vmtest-bpf-VM_Test-7 success Logs for build for x86_64 with llvm-16
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bpf/vmtest-bpf-PR success PR summary
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Commit Message

Hou Tao Nov. 11, 2022, 9:26 a.m. UTC 
From: Hou Tao <houtao1@huawei.com>

Adjusting the size of ring buffer when probing ring buffer map, else
the probe may fail on host with 64KB page size (e.g., an ARM64 host).

After the fix, the output of "bpftool feature" on above host will be
correct.

Before :
    eBPF map_type ringbuf is NOT available
    eBPF map_type user_ringbuf is NOT available

After :
    eBPF map_type ringbuf is available
    eBPF map_type user_ringbuf is available

Signed-off-by: Hou Tao <houtao1@huawei.com>
---
 tools/lib/bpf/libbpf.c          | 2 +-
 tools/lib/bpf/libbpf_internal.h | 2 ++
 tools/lib/bpf/libbpf_probes.c   | 2 +-
 3 files changed, 4 insertions(+), 2 deletions(-)

Comments

Stanislav Fomichev Nov. 11, 2022, 5:47 p.m. UTC | #1 
On 11/11, Hou Tao wrote:
> From: Hou Tao <houtao1@huawei.com>

> Adjusting the size of ring buffer when probing ring buffer map, else
> the probe may fail on host with 64KB page size (e.g., an ARM64 host).

> After the fix, the output of "bpftool feature" on above host will be
> correct.

> Before :
>      eBPF map_type ringbuf is NOT available
>      eBPF map_type user_ringbuf is NOT available

> After :
>      eBPF map_type ringbuf is available
>      eBPF map_type user_ringbuf is available

> Signed-off-by: Hou Tao <houtao1@huawei.com>
> ---
>   tools/lib/bpf/libbpf.c          | 2 +-
>   tools/lib/bpf/libbpf_internal.h | 2 ++
>   tools/lib/bpf/libbpf_probes.c   | 2 +-
>   3 files changed, 4 insertions(+), 2 deletions(-)

> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 184ce1684dcd..907f735568ae 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -2353,7 +2353,7 @@ int parse_btf_map_def(const char *map_name, struct  
> btf *btf,
>   	return 0;
>   }

> -static size_t adjust_ringbuf_sz(size_t sz)
> +size_t adjust_ringbuf_sz(size_t sz)
>   {
>   	__u32 page_sz = sysconf(_SC_PAGE_SIZE);
>   	__u32 mul;
> diff --git a/tools/lib/bpf/libbpf_internal.h  
> b/tools/lib/bpf/libbpf_internal.h
> index 377642ff51fc..99dc4d6a19be 100644
> --- a/tools/lib/bpf/libbpf_internal.h
> +++ b/tools/lib/bpf/libbpf_internal.h
> @@ -576,4 +576,6 @@ static inline bool is_pow_of_2(size_t x)
>   #define PROG_LOAD_ATTEMPTS 5
>   int sys_bpf_prog_load(union bpf_attr *attr, unsigned int size, int  
> attempts);

> +size_t adjust_ringbuf_sz(size_t sz);
> +
>   #endif /* __LIBBPF_LIBBPF_INTERNAL_H */
> diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c
> index f3a8e8e74eb8..29a1db2645fd 100644
> --- a/tools/lib/bpf/libbpf_probes.c
> +++ b/tools/lib/bpf/libbpf_probes.c
> @@ -234,7 +234,7 @@ static int probe_map_create(enum bpf_map_type  
> map_type)
>   	case BPF_MAP_TYPE_USER_RINGBUF:
>   		key_size = 0;
>   		value_size = 0;
> -		max_entries = 4096;
> +		max_entries = adjust_ringbuf_sz(4096);

Why not pass PAGE_SIZE directly here? Something like:

max_entries = sysconf(_SC_PAGE_SIZE);

?

>   		break;
>   	case BPF_MAP_TYPE_STRUCT_OPS:
>   		/* we'll get -ENOTSUPP for invalid BTF type ID for struct_ops */
> --
> 2.29.2
Hou Tao Nov. 12, 2022, 2:31 a.m. UTC | #2 
Hi,

On 11/12/2022 1:47 AM, sdf@google.com wrote:
> On 11/11, Hou Tao wrote:
>> From: Hou Tao <houtao1@huawei.com>
>
>> Adjusting the size of ring buffer when probing ring buffer map, else
>> the probe may fail on host with 64KB page size (e.g., an ARM64 host).
>
>> After the fix, the output of "bpftool feature" on above host will be
>> correct.
>
>> Before :
>>      eBPF map_type ringbuf is NOT available
>>      eBPF map_type user_ringbuf is NOT available
>
>> After :
>>      eBPF map_type ringbuf is available
>>      eBPF map_type user_ringbuf is available
>
>> Signed-off-by: Hou Tao <houtao1@huawei.com>
>> ---
>>   tools/lib/bpf/libbpf.c          | 2 +-
>>   tools/lib/bpf/libbpf_internal.h | 2 ++
>>   tools/lib/bpf/libbpf_probes.c   | 2 +-
>>   3 files changed, 4 insertions(+), 2 deletions(-)
SNIP
>
>>   #endif /* __LIBBPF_LIBBPF_INTERNAL_H */
>> diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c
>> index f3a8e8e74eb8..29a1db2645fd 100644
>> --- a/tools/lib/bpf/libbpf_probes.c
>> +++ b/tools/lib/bpf/libbpf_probes.c
>> @@ -234,7 +234,7 @@ static int probe_map_create(enum bpf_map_type map_type)
>>       case BPF_MAP_TYPE_USER_RINGBUF:
>>           key_size = 0;
>>           value_size = 0;
>> -        max_entries = 4096;
>> +        max_entries = adjust_ringbuf_sz(4096);
>
> Why not pass PAGE_SIZE directly here? Something like:
>
> max_entries = sysconf(_SC_PAGE_SIZE);
>
> ?
Good idea. Will do that in v2.
>
>>           break;
>>       case BPF_MAP_TYPE_STRUCT_OPS:
>>           /* we'll get -ENOTSUPP for invalid BTF type ID for struct_ops */
>> -- 
>> 2.29.2
diff mbox series

Patch

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 184ce1684dcd..907f735568ae 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -2353,7 +2353,7 @@  int parse_btf_map_def(const char *map_name, struct btf *btf,
 	return 0;
 }
 
-static size_t adjust_ringbuf_sz(size_t sz)
+size_t adjust_ringbuf_sz(size_t sz)
 {
 	__u32 page_sz = sysconf(_SC_PAGE_SIZE);
 	__u32 mul;
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 377642ff51fc..99dc4d6a19be 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -576,4 +576,6 @@  static inline bool is_pow_of_2(size_t x)
 #define PROG_LOAD_ATTEMPTS 5
 int sys_bpf_prog_load(union bpf_attr *attr, unsigned int size, int attempts);
 
+size_t adjust_ringbuf_sz(size_t sz);
+
 #endif /* __LIBBPF_LIBBPF_INTERNAL_H */
diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c
index f3a8e8e74eb8..29a1db2645fd 100644
--- a/tools/lib/bpf/libbpf_probes.c
+++ b/tools/lib/bpf/libbpf_probes.c
@@ -234,7 +234,7 @@  static int probe_map_create(enum bpf_map_type map_type)
 	case BPF_MAP_TYPE_USER_RINGBUF:
 		key_size = 0;
 		value_size = 0;
-		max_entries = 4096;
+		max_entries = adjust_ringbuf_sz(4096);
 		break;
 	case BPF_MAP_TYPE_STRUCT_OPS:
 		/* we'll get -ENOTSUPP for invalid BTF type ID for struct_ops */