On Fri, Oct 24, 2025 at 3:54 PM lijiang <[email protected]> wrote:
>
> On Mon, Sep 15, 2025 at 1:16 PM <[email protected]>
> wrote:
>>
>> Date: Thu, 11 Sep 2025 15:20:23 +1200
>> From: Tao Liu <[email protected]>
>> Subject: [Crash-utility] [PATCH] bpf: Implement ringbuf_map memory
>> usage calculation
>> To: [email protected]
>> Cc: Tao Liu <[email protected]>
>> Message-ID: <[email protected]>
>> Content-Type: text/plain; charset="US-ASCII"; x-default=true
>>
>> This patch replicates the kernel code for bpf ringbuf_map mm usage
>> calculation.
>>
>> $ bpftool map create /sys/fs/bpf/rb0 type ringbuf key 0 value 0 entries
>> $((1<<24)) name rb0
>>
>> Before:
>> crash> bpf -m 12
>> ID BPF_MAP BPF_MAP_TYPE MAP_FLAGS
>> 12 ffff8dc4d7c0ed00 RINGBUF 00000000
>> KEY_SIZE: 0 VALUE_SIZE: 0 MAX_ENTRIES: 16777216 MEMLOCK: (unknown)
>> NAME: "rb0" UID: (unused)
>>
>> After:
>> crash> bpf -m 12
>> ID BPF_MAP BPF_MAP_TYPE MAP_FLAGS
>> 12 ffff8dc4d7c0ed00 RINGBUF 00000000
>> KEY_SIZE: 0 VALUE_SIZE: 0 MAX_ENTRIES: 16777216 MEMLOCK: 16855320
>> NAME: "rb0" UID: (unused)
>>
>> Thus, the output will be the same as bpftool:
>>
>> $ bpftool map show id 12
>> 12: ringbuf name rb0 flags 0x0
>> key 0B value 0B max_entries 16777216 memlock 16855320B
>>
>> Signed-off-by: Tao Liu <[email protected]>
>> ---
>> bpf.c | 30 +++++++++++++++++++++++++++++-
>> defs.h | 5 +++++
>> symbols.c | 5 +++++
>> 3 files changed, 39 insertions(+), 1 deletion(-)
>>
>> diff --git a/bpf.c b/bpf.c
>> index 466b244..43e4ff5 100644
>> --- a/bpf.c
>> +++ b/bpf.c
>> @@ -121,6 +121,26 @@ static ulong bpf_map_memory_size(int map_type, uint
>> value_size,
>> return roundup((max_entries * size), PAGESIZE());
>> }
>>
>> +/*
>> + * Code replicated from kernel/bpf/ringbuf.c:ringbuf_map_mem_usage()
>> +*/
>> +static ulong ringbuf_map_mem_usage(struct bpf_info *bpf, int i)
>> +{
>> + ulong nr_pages;
>> + ulong usage = SIZE(bpf_ringbuf_map);
>> + ulong rb = (ulong)(bpf->maplist[i].value) -
>> OFFSET(bpf_ringbuf_map_map)
>> + + OFFSET(bpf_ringbuf_map_rb);
>> + readmem(rb, KVADDR, &rb, sizeof(ulong), "bpf_ringbuf *",
>> RETURN_ON_ERROR);
>
>
> It should be good to use the "FAULT_ON_ERROR" in readmem(), or you can check
> the returned error(if any) here. Both are fine to me.
>
Sure, I will update it when merge.
Thanks,
Tao Liu
>> + readmem(rb + OFFSET(bpf_ringbuf_nr_pages), KVADDR, &nr_pages,
>> + sizeof(ulong), "bpf_ringbuf.nr_pages", RETURN_ON_ERROR);
>
>
> Ditto.
>
> Other changes are good for me.
>
> Thanks
> Lianbo
>
>> + usage += (nr_pages << PAGESHIFT());
>> + ulong nr_meta_pages = (OFFSET(bpf_ringbuf_consumer_pos) >>
>> PAGESHIFT()) + 2;
>> + ulong nr_data_pages = UINT(bpf->bpf_map_buf +
>> OFFSET(bpf_map_max_entries)) >> PAGESHIFT();
>> + usage += (nr_meta_pages + 2 * nr_data_pages) * sizeof(void *);
>> +
>> + return usage;
>> +}
>> +
>> void
>> cmd_bpf(void)
>> {
>> @@ -217,6 +237,7 @@ bpf_init(struct bpf_info *bpf)
>> STRUCT_SIZE_INIT(bpf_prog_aux, "bpf_prog_aux");
>> STRUCT_SIZE_INIT(bpf_map, "bpf_map");
>> STRUCT_SIZE_INIT(bpf_insn, "bpf_insn");
>> + STRUCT_SIZE_INIT(bpf_ringbuf_map, "bpf_ringbuf_map");
>> MEMBER_OFFSET_INIT(bpf_prog_aux, "bpf_prog", "aux");
>> MEMBER_OFFSET_INIT(bpf_prog_type, "bpf_prog", "type");
>> MEMBER_OFFSET_INIT(bpf_prog_tag, "bpf_prog", "tag");
>> @@ -228,6 +249,10 @@ bpf_init(struct bpf_info *bpf)
>> MEMBER_OFFSET_INIT(bpf_map_map_flags, "bpf_map",
>> "map_flags");
>> MEMBER_OFFSET_INIT(bpf_prog_aux_used_maps, "bpf_prog_aux",
>> "used_maps");
>> MEMBER_OFFSET_INIT(bpf_prog_aux_used_map_cnt,
>> "bpf_prog_aux", "used_map_cnt");
>> + MEMBER_OFFSET_INIT(bpf_ringbuf_map_map, "bpf_ringbuf_map",
>> "map");
>> + MEMBER_OFFSET_INIT(bpf_ringbuf_map_rb, "bpf_ringbuf_map",
>> "rb");
>> + MEMBER_OFFSET_INIT(bpf_ringbuf_consumer_pos, "bpf_ringbuf",
>> "consumer_pos");
>> + MEMBER_OFFSET_INIT(bpf_ringbuf_nr_pages, "bpf_ringbuf",
>> "nr_pages");
>> if (!VALID_STRUCT(bpf_prog) ||
>> !VALID_STRUCT(bpf_prog_aux) ||
>> !VALID_STRUCT(bpf_map) ||
>> @@ -664,7 +689,10 @@ do_map_only:
>> fprintf(fp, "%d\n", map_pages * PAGESIZE());
>> } else if ((msize = bpf_map_memory_size(type,
>> value_size, key_size, max_entries)))
>> fprintf(fp, "%ld\n", msize);
>> - else
>> +#define BPF_MAP_TYPE_RINGBUF (0x1BUL)
>> + else if (type == BPF_MAP_TYPE_RINGBUF) {
>> + fprintf(fp, "%ld\n",
>> ringbuf_map_mem_usage(bpf, i));
>> + } else
>> fprintf(fp, "(unknown)");
>>
>> fprintf(fp, " NAME: ");
>> diff --git a/defs.h b/defs.h
>> index 4fecb83..498c262 100644
>> --- a/defs.h
>> +++ b/defs.h
>> @@ -2274,6 +2274,10 @@ struct offset_table { /* stash of
>> commonly-used offsets */
>> long request_queue_tag_set;
>> long blk_mq_tag_set_flags;
>> long blk_mq_tag_set_shared_tags;
>> + long bpf_ringbuf_map_map;
>> + long bpf_ringbuf_map_rb;
>> + long bpf_ringbuf_consumer_pos;
>> + long bpf_ringbuf_nr_pages;
>> };
>>
>> struct size_table { /* stash of commonly-used sizes */
>> @@ -2452,6 +2456,7 @@ struct size_table { /* stash of commonly-used
>> sizes */
>> long vmap_node;
>> long cpumask_t;
>> long task_struct_exit_state;
>> + long bpf_ringbuf_map;
>> };
>>
>> struct array_table {
>> diff --git a/symbols.c b/symbols.c
>> index ce0b441..19e1316 100644
>> --- a/symbols.c
>> +++ b/symbols.c
>> @@ -11868,6 +11868,10 @@ dump_offset_table(char *spec, ulong makestruct)
>> fprintf(fp, " thread_struct_gsbase: %ld\n",
>> OFFSET(thread_struct_gsbase));
>> fprintf(fp, " thread_struct_fs: %ld\n",
>> OFFSET(thread_struct_fs));
>> fprintf(fp, " thread_struct_gs: %ld\n",
>> OFFSET(thread_struct_gs));
>> + fprintf(fp, " bpf_ringbuf_map_map: %ld\n",
>> OFFSET(bpf_ringbuf_map_map));
>> + fprintf(fp, " bpf_ringbuf_map_rb: %ld\n",
>> OFFSET(bpf_ringbuf_map_rb));
>> + fprintf(fp, " bpf_ringbuf_consumer_pos: %ld\n",
>> OFFSET(bpf_ringbuf_consumer_pos));
>> + fprintf(fp, " bpf_ringbuf_nr_pages: %ld\n",
>> OFFSET(bpf_ringbuf_nr_pages));
>>
>> fprintf(fp, "\n size_table:\n");
>> fprintf(fp, " page: %ld\n", SIZE(page));
>> @@ -12148,6 +12152,7 @@ dump_offset_table(char *spec, ulong makestruct)
>>
>> fprintf(fp, " percpu_counter: %ld\n",
>> SIZE(percpu_counter));
>> fprintf(fp, " cpumask_t: %ld\n",
>> SIZE(cpumask_t));
>> + fprintf(fp, " bpf_ringbuf_map: %ld\n",
>> SIZE(bpf_ringbuf_map));
>>
>> fprintf(fp, "\n array_table:\n");
>> /*
>> --
>> 2.47.0
--
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