[PATCH bpf-next v2 0/3] Add overwrite mode for bpf ring buffer

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Xu Kuohai

5 Sep 2025 5 Sep '25

3:06 p.m.

When the bpf ring buffer is full, new events can not be recorded util the consumer consumes some events to free space. This may cause critical events to be discarded, such as in fault diagnostic, where recent events are more critical than older ones.

So add ovewrite mode for bpf ring buffer. In this mode, the new event overwrites the oldest event when the buffer is full.

v2: - remove libbpf changes (Andrii) - update overwrite benchmark

v1: https://lore.kernel.org/bpf/20250804022101.2171981-1-xukuohai@huaweicloud.co...

Xu Kuohai (3): bpf: Add overwrite mode for bpf ring buffer selftests/bpf: Add test for overwrite ring buffer selftests/bpf/benchs: Add producer and overwrite bench for ring buffer

include/uapi/linux/bpf.h | 4 + kernel/bpf/ringbuf.c | 159 +++++++++++++++--- tools/include/uapi/linux/bpf.h | 4 + tools/testing/selftests/bpf/Makefile | 3 +- tools/testing/selftests/bpf/bench.c | 2 + .../selftests/bpf/benchs/bench_ringbufs.c | 95 ++++++++++- .../bpf/benchs/run_bench_ringbufs.sh | 4 + .../selftests/bpf/prog_tests/ringbuf.c | 74 ++++++++ .../selftests/bpf/progs/ringbuf_bench.c | 10 ++ .../bpf/progs/test_ringbuf_overwrite.c | 98 +++++++++++ 10 files changed, 418 insertions(+), 35 deletions(-) create mode 100644 tools/testing/selftests/bpf/progs/test_ringbuf_overwrite.c

-- 2.43.0

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Xu Kuohai

5 Sep 5 Sep

3:06 p.m.

New subject: [PATCH bpf-next v2 1/3] bpf: Add overwrite mode for bpf ring buffer

From: Xu Kuohai xukuohai@huawei.com

So add ovewrite mode for bpf ring buffer. In this mode, the new event overwrites the oldest event when the buffer is full.

The scheme is as follows:

1. producer_pos tracks the next position to write new data. When there is enough free space, producer simply moves producer_pos forward to make space for the new event.

2. To avoid waiting for consumer to free space when the buffer is full, a new variable overwrite_pos is introduced for producer. overwrite_pos tracks the next event to be overwritten (the oldest event committed) in the buffer. producer moves it forward to discard the oldest events when the buffer is full.

3. pending_pos tracks the oldest event under committing. producer ensures producers_pos never passes pending_pos when making space for new events. So multiple producers never write to the same position at the same time.

4. producer wakes up consumer every half a round ahead to give it a chance to retrieve data. However, for an overwrite-mode ring buffer, users typically only cares about the ring buffer snapshot before a fault occurs. In this case, the producer should commit data with BPF_RB_NO_WAKEUP flag to avoid unnecessary wakeups.

To make it clear, here are some example diagrams.

1. Let's say we have a ring buffer with size 4096.

At first, {producer,overwrite,pending,consumer}_pos are all set to 0

0 512 1024 1536 2048 2560 3072 3584 4096 +-----------------------------------------------------------------------+ | | | | | | +-----------------------------------------------------------------------+ ^ | | producer_pos = 0 overwrite_pos = 0 pending_pos = 0 consumer_pos = 0

2. Reserve event A, size 512.

There is enough free space, so A is allocated at offset 0 and producer_pos is moved to 512, the end of A. Since A is not submitted, the BUSY bit is set.

0 512 1024 1536 2048 2560 3072 3584 4096 +-----------------------------------------------------------------------+ | | | | A | | | [BUSY] | | +-----------------------------------------------------------------------+ ^ ^ | | | | | producer_pos = 512 | overwrite_pos = 0 pending_pos = 0 consumer_pos = 0

3. Reserve event B, size 1024.

B is allocated at offset 512 with BUSY bit set, and producer_pos is moved to the end of B.

0 512 1024 1536 2048 2560 3072 3584 4096 +-----------------------------------------------------------------------+ | | | | | A | B | | | [BUSY] | [BUSY] | | +-----------------------------------------------------------------------+ ^ ^ | | | | | producer_pos = 1536 | overwrite_pos = 0 pending_pos = 0 consumer_pos = 0

4. Reserve event C, size 2048.

C is allocated at offset 1536 and producer_pos becomes 3584.

0 512 1024 1536 2048 2560 3072 3584 4096 +-----------------------------------------------------------------------+ | | | | | | A | B | C | | | [BUSY] | [BUSY] | [BUSY] | | +-----------------------------------------------------------------------+ ^ ^ | | | | | producer_pos = 3584 | overwrite_pos = 0 pending_pos = 0 consumer_pos = 0

5. Submit event A.

The BUSY bit of A is cleared. B becomes the oldest event under writing, so pending_pos is moved to 512, the start of B.

0 512 1024 1536 2048 2560 3072 3584 4096 +-----------------------------------------------------------------------+ | | | | | | A | B | C | | | | [BUSY] | [BUSY] | | +-----------------------------------------------------------------------+ ^ ^ ^ | | | | | | | pending_pos = 512 producer_pos = 3584 | overwrite_pos = 0 consumer_pos = 0

6. Submit event B.

The BUSY bit of B is cleared, and pending_pos is moved to the start of C, which is the oldest event under writing now.

0 512 1024 1536 2048 2560 3072 3584 4096 +-----------------------------------------------------------------------+ | | | | | | A | B | C | | | | | [BUSY] | | +-----------------------------------------------------------------------+ ^ ^ ^ | | | | | | | pending_pos = 1536 producer_pos = 3584 | overwrite_pos = 0 consumer_pos = 0

7. Reserve event D, size 1536 (3 * 512).

There are 2048 bytes not under writing between producer_pos and pending_pos, so D is allocated at offset 3584, and producer_pos is moved from 3584 to 5120.

Since event D will overwrite all bytes of event A and the begining 512 bytes of event B, overwrite_pos is moved to the start of event C, the oldest event that is not overwritten.

8. Reserve event E, size 1024.

Though there are 512 bytes not under writing between producer_pos and pending_pos, E can not be reserved, as it would overwrite the first 512 bytes of event C, which is still under writing.

9. Submit event C and D.

pending_pos is moved to the end of D.

The performance data for overwrite mode will be provided in a follow-up patch that adds overwrite mode benchs.

A sample of performance data for non-overwrite mode on an x86_64 and arm64 CPU, before and after this patch, is shown below. As we can see, no obvious performance regression occurs.

- x86_64 (AMD EPYC 9654)

Before:

Ringbuf, multi-producer contention ================================== rb-libbpf nr_prod 1 13.218 ± 0.039M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 2 15.684 ± 0.015M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 3 7.771 ± 0.002M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 4 6.281 ± 0.001M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 8 2.842 ± 0.003M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 12 2.001 ± 0.004M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 16 1.833 ± 0.003M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 20 1.508 ± 0.003M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 24 1.421 ± 0.002M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 28 1.309 ± 0.001M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 32 1.265 ± 0.003M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 36 1.198 ± 0.002M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 40 1.174 ± 0.001M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 44 1.113 ± 0.003M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 48 1.097 ± 0.002M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 52 1.070 ± 0.002M/s (drops 0.000 ± 0.000M/s)

After:

Ringbuf, multi-producer contention ================================== rb-libbpf nr_prod 1 13.751 ± 0.673M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 2 15.592 ± 0.008M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 3 7.776 ± 0.002M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 4 6.463 ± 0.002M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 8 2.883 ± 0.003M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 12 2.017 ± 0.003M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 16 1.816 ± 0.004M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 20 1.512 ± 0.003M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 24 1.396 ± 0.002M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 28 1.303 ± 0.002M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 32 1.267 ± 0.002M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 36 1.210 ± 0.002M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 40 1.181 ± 0.002M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 44 1.136 ± 0.002M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 48 1.090 ± 0.001M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 52 1.091 ± 0.002M/s (drops 0.000 ± 0.000M/s)

- arm64 (HiSilicon Kunpeng 920)

Before:

Ringbuf, multi-producer contention ================================== rb-libbpf nr_prod 1 11.602 ± 0.423M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 2 9.599 ± 0.007M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 3 6.669 ± 0.008M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 4 4.806 ± 0.002M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 8 3.856 ± 0.002M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 12 3.368 ± 0.003M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 16 3.210 ± 0.007M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 20 3.003 ± 0.007M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 24 2.944 ± 0.007M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 28 2.863 ± 0.008M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 32 2.819 ± 0.007M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 36 2.887 ± 0.008M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 40 2.837 ± 0.008M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 44 2.787 ± 0.012M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 48 2.738 ± 0.010M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 52 2.700 ± 0.007M/s (drops 0.000 ± 0.000M/s)

After:

Ringbuf, multi-producer contention ================================== rb-libbpf nr_prod 1 11.614 ± 0.268M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 2 9.917 ± 0.007M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 3 6.920 ± 0.008M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 4 4.803 ± 0.002M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 8 3.898 ± 0.002M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 12 3.426 ± 0.008M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 16 3.320 ± 0.008M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 20 3.029 ± 0.013M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 24 3.068 ± 0.012M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 28 2.890 ± 0.009M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 32 2.950 ± 0.012M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 36 2.812 ± 0.006M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 40 2.834 ± 0.009M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 44 2.803 ± 0.010M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 48 2.766 ± 0.010M/s (drops 0.000 ± 0.000M/s) rb-libbpf nr_prod 52 2.754 ± 0.009M/s (drops 0.000 ± 0.000M/s)

Signed-off-by: Xu Kuohai xukuohai@huawei.com --- include/uapi/linux/bpf.h | 4 + kernel/bpf/ringbuf.c | 159 +++++++++++++++++++++++++++------ tools/include/uapi/linux/bpf.h | 4 + 3 files changed, 141 insertions(+), 26 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 233de8677382..d3b2fd2ae527 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -1430,6 +1430,9 @@ enum {

/* Do not translate kernel bpf_arena pointers to user pointers */ BPF_F_NO_USER_CONV = (1U << 18), + +/* bpf ringbuf works in overwrite mode? */ + BPF_F_OVERWRITE = (1U << 19), };

/* Flags for BPF_PROG_QUERY. */ @@ -6215,6 +6218,7 @@ enum { BPF_RB_RING_SIZE = 1, BPF_RB_CONS_POS = 2, BPF_RB_PROD_POS = 3, + BPF_RB_OVER_POS = 4, };

/* BPF ring buffer constants */ diff --git a/kernel/bpf/ringbuf.c b/kernel/bpf/ringbuf.c index 719d73299397..6ca41d01f187 100644 --- a/kernel/bpf/ringbuf.c +++ b/kernel/bpf/ringbuf.c @@ -13,7 +13,7 @@ #include <linux/btf_ids.h> #include <asm/rqspinlock.h>

-#define RINGBUF_CREATE_FLAG_MASK (BPF_F_NUMA_NODE) +#define RINGBUF_CREATE_FLAG_MASK (BPF_F_NUMA_NODE | BPF_F_OVERWRITE)

/* non-mmap()'able part of bpf_ringbuf (everything up to consumer page) */ #define RINGBUF_PGOFF \ @@ -27,7 +27,8 @@ struct bpf_ringbuf { wait_queue_head_t waitq; struct irq_work work; - u64 mask; + u64 mask:48; + u64 overwrite_mode:1; struct page **pages; int nr_pages; rqspinlock_t spinlock ____cacheline_aligned_in_smp; @@ -72,6 +73,7 @@ struct bpf_ringbuf { */ unsigned long consumer_pos __aligned(PAGE_SIZE); unsigned long producer_pos __aligned(PAGE_SIZE); + unsigned long overwrite_pos; /* to be overwritten in overwrite mode */ unsigned long pending_pos; char data[] __aligned(PAGE_SIZE); }; @@ -166,7 +168,8 @@ static void bpf_ringbuf_notify(struct irq_work *work) * considering that the maximum value of data_sz is (4GB - 1), there * will be no overflow, so just note the size limit in the comments. */ -static struct bpf_ringbuf *bpf_ringbuf_alloc(size_t data_sz, int numa_node) +static struct bpf_ringbuf *bpf_ringbuf_alloc(size_t data_sz, int numa_node, + int overwrite_mode) { struct bpf_ringbuf *rb;

@@ -183,17 +186,25 @@ static struct bpf_ringbuf *bpf_ringbuf_alloc(size_t data_sz, int numa_node) rb->consumer_pos = 0; rb->producer_pos = 0; rb->pending_pos = 0; + rb->overwrite_mode = overwrite_mode;

return rb; }

static struct bpf_map *ringbuf_map_alloc(union bpf_attr *attr) { + int overwrite_mode = 0; struct bpf_ringbuf_map *rb_map;

if (attr->map_flags & ~RINGBUF_CREATE_FLAG_MASK) return ERR_PTR(-EINVAL);

+ if (attr->map_flags & BPF_F_OVERWRITE) { + if (attr->map_type == BPF_MAP_TYPE_USER_RINGBUF) + return ERR_PTR(-EINVAL); + overwrite_mode = 1; + } + if (attr->key_size || attr->value_size || !is_power_of_2(attr->max_entries) || !PAGE_ALIGNED(attr->max_entries)) @@ -205,7 +216,8 @@ static struct bpf_map *ringbuf_map_alloc(union bpf_attr *attr)

bpf_map_init_from_attr(&rb_map->map, attr);

- rb_map->rb = bpf_ringbuf_alloc(attr->max_entries, rb_map->map.numa_node); + rb_map->rb = bpf_ringbuf_alloc(attr->max_entries, rb_map->map.numa_node, + overwrite_mode); if (!rb_map->rb) { bpf_map_area_free(rb_map); return ERR_PTR(-ENOMEM); @@ -295,11 +307,16 @@ static int ringbuf_map_mmap_user(struct bpf_map *map, struct vm_area_struct *vma

static unsigned long ringbuf_avail_data_sz(struct bpf_ringbuf *rb) { - unsigned long cons_pos, prod_pos; + unsigned long cons_pos, prod_pos, over_pos;

cons_pos = smp_load_acquire(&rb->consumer_pos); prod_pos = smp_load_acquire(&rb->producer_pos); - return prod_pos - cons_pos; + + if (likely(!rb->overwrite_mode)) + return prod_pos - cons_pos; + + over_pos = READ_ONCE(rb->overwrite_pos); + return min(prod_pos - max(cons_pos, over_pos), rb->mask + 1); }

static u32 ringbuf_total_data_sz(const struct bpf_ringbuf *rb) @@ -402,11 +419,43 @@ bpf_ringbuf_restore_from_rec(struct bpf_ringbuf_hdr *hdr) return (void*)((addr & PAGE_MASK) - off); }

+ +static bool bpf_ringbuf_has_space(const struct bpf_ringbuf *rb, + unsigned long new_prod_pos, + unsigned long cons_pos, + unsigned long pend_pos) +{ + /* no space if oldest not yet committed record until the newest + * record span more than (ringbuf_size - 1) + */ + if (new_prod_pos - pend_pos > rb->mask) + return false; + + /* ok, we have space in ovewrite mode */ + if (unlikely(rb->overwrite_mode)) + return true; + + /* no space if producer position advances more than (ringbuf_size - 1) + * ahead than consumer position when not in overwrite mode + */ + if (new_prod_pos - cons_pos > rb->mask) + return false; + + return true; +} + +static u32 ringbuf_round_up_hdr_len(u32 hdr_len) +{ + hdr_len &= ~BPF_RINGBUF_DISCARD_BIT; + return round_up(hdr_len + BPF_RINGBUF_HDR_SZ, 8); +} + static void *__bpf_ringbuf_reserve(struct bpf_ringbuf *rb, u64 size) { - unsigned long cons_pos, prod_pos, new_prod_pos, pend_pos, flags; + unsigned long flags; struct bpf_ringbuf_hdr *hdr; - u32 len, pg_off, tmp_size, hdr_len; + u32 len, pg_off, hdr_len; + unsigned long cons_pos, prod_pos, new_prod_pos, pend_pos, over_pos;

if (unlikely(size > RINGBUF_MAX_RECORD_SZ)) return NULL; @@ -429,24 +478,39 @@ static void *__bpf_ringbuf_reserve(struct bpf_ringbuf *rb, u64 size) hdr_len = READ_ONCE(hdr->len); if (hdr_len & BPF_RINGBUF_BUSY_BIT) break; - tmp_size = hdr_len & ~BPF_RINGBUF_DISCARD_BIT; - tmp_size = round_up(tmp_size + BPF_RINGBUF_HDR_SZ, 8); - pend_pos += tmp_size; + pend_pos += ringbuf_round_up_hdr_len(hdr_len); } rb->pending_pos = pend_pos;

- /* check for out of ringbuf space: - * - by ensuring producer position doesn't advance more than - * (ringbuf_size - 1) ahead - * - by ensuring oldest not yet committed record until newest - * record does not span more than (ringbuf_size - 1) - */ - if (new_prod_pos - cons_pos > rb->mask || - new_prod_pos - pend_pos > rb->mask) { + if (!bpf_ringbuf_has_space(rb, new_prod_pos, cons_pos, pend_pos)) { raw_res_spin_unlock_irqrestore(&rb->spinlock, flags); return NULL; }

+ /* In overwrite mode, move overwrite_pos to the next record to be + * overwritten if the ring buffer is full + */ + if (unlikely(rb->overwrite_mode)) { + over_pos = rb->overwrite_pos; + while (new_prod_pos - over_pos > rb->mask) { + hdr = (void *)rb->data + (over_pos & rb->mask); + hdr_len = READ_ONCE(hdr->len); + /* since pending_pos is the first record with BUSY + * bit set and overwrite_pos is never bigger than + * pending_pos, no need to check BUSY bit here. + */ + over_pos += ringbuf_round_up_hdr_len(hdr_len); + } + /* smp_store_release(&rb->producer_pos, new_prod_pos) at + * the end of the function ensures that when consumer sees + * the updated rb->producer_pos, it always sees the updated + * rb->overwrite_pos, so when consumer reads overwrite_pos + * after smp_load_acquire(r->producer_pos), the overwrite_pos + * will always be valid. + */ + WRITE_ONCE(rb->overwrite_pos, over_pos); + } + hdr = (void *)rb->data + (prod_pos & rb->mask); pg_off = bpf_ringbuf_rec_pg_off(rb, hdr); hdr->len = size | BPF_RINGBUF_BUSY_BIT; @@ -479,7 +543,50 @@ const struct bpf_func_proto bpf_ringbuf_reserve_proto = { .arg3_type = ARG_ANYTHING, };

-static void bpf_ringbuf_commit(void *sample, u64 flags, bool discard) +static __always_inline +bool ringbuf_should_wakeup(const struct bpf_ringbuf *rb, + unsigned long rec_pos, + unsigned long cons_pos, + u32 len, u64 flags) +{ + unsigned long rec_end; + + if (flags & BPF_RB_FORCE_WAKEUP) + return true; + + if (flags & BPF_RB_NO_WAKEUP) + return false; + + /* for non-overwrite mode, if consumer caught up and is waiting for + * our record, notify about new data availability + */ + if (likely(!rb->overwrite_mode)) + return cons_pos == rec_pos; + + /* for overwrite mode, to give the consumer a chance to catch up + * before being overwritten, wake up consumer every half a round + * ahead. + */ + rec_end = rec_pos + ringbuf_round_up_hdr_len(len); + + cons_pos &= (rb->mask >> 1); + rec_pos &= (rb->mask >> 1); + rec_end &= (rb->mask >> 1); + + if (cons_pos == rec_pos) + return true; + + if (rec_pos < cons_pos && cons_pos < rec_end) + return true; + + if (rec_end < rec_pos && (cons_pos > rec_pos || cons_pos < rec_end)) + return true; + + return false; +} + +static __always_inline +void bpf_ringbuf_commit(void *sample, u64 flags, bool discard) { unsigned long rec_pos, cons_pos; struct bpf_ringbuf_hdr *hdr; @@ -495,15 +602,10 @@ static void bpf_ringbuf_commit(void *sample, u64 flags, bool discard) /* update record header with correct final size prefix */ xchg(&hdr->len, new_len);

- /* if consumer caught up and is waiting for our record, notify about - * new data availability - */ rec_pos = (void *)hdr - (void *)rb->data; cons_pos = smp_load_acquire(&rb->consumer_pos) & rb->mask;

- if (flags & BPF_RB_FORCE_WAKEUP) - irq_work_queue(&rb->work); - else if (cons_pos == rec_pos && !(flags & BPF_RB_NO_WAKEUP)) + if (ringbuf_should_wakeup(rb, rec_pos, cons_pos, new_len, flags)) irq_work_queue(&rb->work); }

@@ -576,6 +678,8 @@ BPF_CALL_2(bpf_ringbuf_query, struct bpf_map *, map, u64, flags) return smp_load_acquire(&rb->consumer_pos); case BPF_RB_PROD_POS: return smp_load_acquire(&rb->producer_pos); + case BPF_RB_OVER_POS: + return READ_ONCE(rb->overwrite_pos); default: return 0; } @@ -749,6 +853,9 @@ BPF_CALL_4(bpf_user_ringbuf_drain, struct bpf_map *, map,

rb = container_of(map, struct bpf_ringbuf_map, map)->rb;

+ if (unlikely(rb->overwrite_mode)) + return -EOPNOTSUPP; + /* If another consumer is already consuming a sample, wait for them to finish. */ if (!atomic_try_cmpxchg(&rb->busy, &busy, 1)) return -EBUSY; diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index 233de8677382..d3b2fd2ae527 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -1430,6 +1430,9 @@ enum {

/* Do not translate kernel bpf_arena pointers to user pointers */ BPF_F_NO_USER_CONV = (1U << 18), + +/* bpf ringbuf works in overwrite mode? */ + BPF_F_OVERWRITE = (1U << 19), };

/* Flags for BPF_PROG_QUERY. */ @@ -6215,6 +6218,7 @@ enum { BPF_RB_RING_SIZE = 1, BPF_RB_CONS_POS = 2, BPF_RB_PROD_POS = 3, + BPF_RB_OVER_POS = 4, };

/* BPF ring buffer constants */

-- 2.43.0

Xu Kuohai

3:06 p.m.

New subject: [PATCH bpf-next v2 2/3] selftests/bpf: Add test for overwrite ring buffer

From: Xu Kuohai xukuohai@huawei.com

Add test for overwiret mode ring buffer. The test creates a bpf ring buffer in overwrite mode, then repeatlly reserves and commits data to check if the ring buffer works as expected both before and after overwrite happens.

Signed-off-by: Xu Kuohai xukuohai@huawei.com --- tools/testing/selftests/bpf/Makefile | 3 +- .../selftests/bpf/prog_tests/ringbuf.c | 74 ++++++++++++++ .../bpf/progs/test_ringbuf_overwrite.c | 98 +++++++++++++++++++ 3 files changed, 174 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/bpf/progs/test_ringbuf_overwrite.c

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile index 11d2a368db3e..e6c18e201555 100644 --- a/tools/testing/selftests/bpf/Makefile +++ b/tools/testing/selftests/bpf/Makefile @@ -499,7 +499,8 @@ LINKED_SKELS := test_static_linked.skel.h linked_funcs.skel.h \ LSKELS := fentry_test.c fexit_test.c fexit_sleep.c atomics.c \ trace_printk.c trace_vprintk.c map_ptr_kern.c \ core_kern.c core_kern_overflow.c test_ringbuf.c \ - test_ringbuf_n.c test_ringbuf_map_key.c test_ringbuf_write.c + test_ringbuf_n.c test_ringbuf_map_key.c test_ringbuf_write.c \ + test_ringbuf_overwrite.c

# Generate both light skeleton and libbpf skeleton for these LSKELS_EXTRA := test_ksyms_module.c test_ksyms_weak.c kfunc_call_test.c \ diff --git a/tools/testing/selftests/bpf/prog_tests/ringbuf.c b/tools/testing/selftests/bpf/prog_tests/ringbuf.c index d1e4cb28a72c..205a51c725a7 100644 --- a/tools/testing/selftests/bpf/prog_tests/ringbuf.c +++ b/tools/testing/selftests/bpf/prog_tests/ringbuf.c @@ -17,6 +17,7 @@ #include "test_ringbuf_n.lskel.h" #include "test_ringbuf_map_key.lskel.h" #include "test_ringbuf_write.lskel.h" +#include "test_ringbuf_overwrite.lskel.h"

#define EDONE 7777

@@ -497,6 +498,77 @@ static void ringbuf_map_key_subtest(void) test_ringbuf_map_key_lskel__destroy(skel_map_key); }

+static void ringbuf_overwrite_mode_subtest(void) +{ + unsigned long size, len1, len2, len3, len4, len5; + unsigned long expect_avail_data, expect_prod_pos, expect_over_pos; + struct test_ringbuf_overwrite_lskel *skel; + int err; + + skel = test_ringbuf_overwrite_lskel__open(); + if (!ASSERT_OK_PTR(skel, "skel_open")) + return; + + size = 0x1000; + len1 = 0x800; + len2 = 0x400; + len3 = size - len1 - len2 - BPF_RINGBUF_HDR_SZ * 3; /* 0x3e8 */ + len4 = len3 - 8; /* 0x3e0 */ + len5 = len3; /* retry with len3 */ + + skel->maps.ringbuf.max_entries = size; + skel->rodata->LEN1 = len1; + skel->rodata->LEN2 = len2; + skel->rodata->LEN3 = len3; + skel->rodata->LEN4 = len4; + skel->rodata->LEN5 = len5; + + skel->bss->pid = getpid(); + + err = test_ringbuf_overwrite_lskel__load(skel); + if (!ASSERT_OK(err, "skel_load")) + goto cleanup; + + err = test_ringbuf_overwrite_lskel__attach(skel); + if (!ASSERT_OK(err, "skel_attach")) + goto cleanup; + + syscall(__NR_getpgid); + + ASSERT_EQ(skel->bss->reserve1_fail, 0, "reserve 1"); + ASSERT_EQ(skel->bss->reserve2_fail, 0, "reserve 2"); + ASSERT_EQ(skel->bss->reserve3_fail, 1, "reserve 3"); + ASSERT_EQ(skel->bss->reserve4_fail, 0, "reserve 4"); + ASSERT_EQ(skel->bss->reserve5_fail, 0, "reserve 5"); + + CHECK(skel->bss->ring_size != size, + "check_ring_size", "exp %lu, got %lu\n", + size, skel->bss->ring_size); + + expect_avail_data = len2 + len4 + len5 + 3 * BPF_RINGBUF_HDR_SZ; + CHECK(skel->bss->avail_data != expect_avail_data, + "check_avail_size", "exp %lu, got %lu\n", + expect_avail_data, skel->bss->avail_data); + + CHECK(skel->bss->cons_pos != 0, + "check_cons_pos", "exp 0, got %lu\n", + skel->bss->cons_pos); + + expect_prod_pos = len1 + len2 + len4 + len5 + 4 * BPF_RINGBUF_HDR_SZ; + CHECK(skel->bss->prod_pos != expect_prod_pos, + "check_prod_pos", "exp %lu, got %lu\n", + expect_prod_pos, skel->bss->prod_pos); + + expect_over_pos = len1 + BPF_RINGBUF_HDR_SZ; + CHECK(skel->bss->over_pos != expect_over_pos, + "check_over_pos", "exp %lu, got %lu\n", + (unsigned long)expect_over_pos, skel->bss->over_pos); + + test_ringbuf_overwrite_lskel__detach(skel); +cleanup: + test_ringbuf_overwrite_lskel__destroy(skel); +} + void test_ringbuf(void) { if (test__start_subtest("ringbuf")) @@ -507,4 +579,6 @@ void test_ringbuf(void) ringbuf_map_key_subtest(); if (test__start_subtest("ringbuf_write")) ringbuf_write_subtest(); + if (test__start_subtest("ringbuf_overwrite_mode")) + ringbuf_overwrite_mode_subtest(); } diff --git a/tools/testing/selftests/bpf/progs/test_ringbuf_overwrite.c b/tools/testing/selftests/bpf/progs/test_ringbuf_overwrite.c new file mode 100644 index 000000000000..da89ba12a75c --- /dev/null +++ b/tools/testing/selftests/bpf/progs/test_ringbuf_overwrite.c @@ -0,0 +1,98 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (C) 2025. Huawei Technologies Co., Ltd */ + +#include <linux/bpf.h> +#include <bpf/bpf_helpers.h> +#include "bpf_misc.h" + +char _license[] SEC("license") = "GPL"; + +struct { + __uint(type, BPF_MAP_TYPE_RINGBUF); + __uint(map_flags, BPF_F_OVERWRITE); +} ringbuf SEC(".maps"); + +int pid; + +const volatile unsigned long LEN1; +const volatile unsigned long LEN2; +const volatile unsigned long LEN3; +const volatile unsigned long LEN4; +const volatile unsigned long LEN5; + +long reserve1_fail = 0; +long reserve2_fail = 0; +long reserve3_fail = 0; +long reserve4_fail = 0; +long reserve5_fail = 0; + +unsigned long avail_data = 0; +unsigned long ring_size = 0; +unsigned long cons_pos = 0; +unsigned long prod_pos = 0; +unsigned long over_pos = 0; + +SEC("fentry/" SYS_PREFIX "sys_getpgid") +int test_overwrite_ringbuf(void *ctx) +{ + char *rec1, *rec2, *rec3, *rec4, *rec5; + int cur_pid = bpf_get_current_pid_tgid() >> 32; + + if (cur_pid != pid) + return 0; + + rec1 = bpf_ringbuf_reserve(&ringbuf, LEN1, 0); + if (!rec1) { + reserve1_fail = 1; + return 0; + } + + rec2 = bpf_ringbuf_reserve(&ringbuf, LEN2, 0); + if (!rec2) { + bpf_ringbuf_discard(rec1, 0); + reserve2_fail = 1; + return 0; + } + + rec3 = bpf_ringbuf_reserve(&ringbuf, LEN3, 0); + /* expect failure */ + if (!rec3) { + reserve3_fail = 1; + } else { + bpf_ringbuf_discard(rec1, 0); + bpf_ringbuf_discard(rec2, 0); + bpf_ringbuf_discard(rec3, 0); + return 0; + } + + rec4 = bpf_ringbuf_reserve(&ringbuf, LEN4, 0); + if (!rec4) { + reserve4_fail = 1; + bpf_ringbuf_discard(rec1, 0); + bpf_ringbuf_discard(rec2, 0); + return 0; + } + + bpf_ringbuf_submit(rec1, 0); + bpf_ringbuf_submit(rec2, 0); + bpf_ringbuf_submit(rec4, 0); + + rec5 = bpf_ringbuf_reserve(&ringbuf, LEN5, 0); + if (!rec5) { + reserve5_fail = 1; + return 0; + } + + for (int i = 0; i < LEN3; i++) + rec5[i] = 0xdd; + + bpf_ringbuf_submit(rec5, 0); + + ring_size = bpf_ringbuf_query(&ringbuf, BPF_RB_RING_SIZE); + avail_data = bpf_ringbuf_query(&ringbuf, BPF_RB_AVAIL_DATA); + cons_pos = bpf_ringbuf_query(&ringbuf, BPF_RB_CONS_POS); + prod_pos = bpf_ringbuf_query(&ringbuf, BPF_RB_PROD_POS); + over_pos = bpf_ringbuf_query(&ringbuf, BPF_RB_OVER_POS); + + return 0; +}

-- 2.43.0

Xu Kuohai

3:06 p.m.

New subject: [PATCH bpf-next v2 3/3] selftests/bpf/benchs: Add producer and overwrite bench for ring buffer

From: Xu Kuohai xukuohai@huawei.com

Add rb-prod test for bpf ring buffer to bench producer performance without counsumer thread. And add --rb-overwrite option to bench ring buffer in overwrite mode.

For reference, below are bench numbers collected from x86_64 and arm64 CPUs.

- AMD EPYC 9654 (x86_64)

Ringbuf, overwrite mode with multi-producer contention, no consumer =================================================================== rb-prod nr_prod 1 32.295 ± 0.004M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 2 9.591 ± 0.003M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 3 8.895 ± 0.002M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 4 9.206 ± 0.003M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 8 9.220 ± 0.002M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 12 4.595 ± 0.022M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 16 4.348 ± 0.016M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 20 3.957 ± 0.017M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 24 3.787 ± 0.014M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 28 3.603 ± 0.011M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 32 3.707 ± 0.011M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 36 3.562 ± 0.012M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 40 3.616 ± 0.012M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 44 3.598 ± 0.016M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 48 3.555 ± 0.014M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 52 3.463 ± 0.020M/s (drops 0.000 ± 0.000M/s)

- HiSilicon Kunpeng 920 (arm64)

Ringbuf, overwrite mode with multi-producer contention, no consumer =================================================================== rb-prod nr_prod 1 14.687 ± 0.058M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 2 22.263 ± 0.007M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 3 5.736 ± 0.003M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 4 4.934 ± 0.001M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 8 4.661 ± 0.001M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 12 3.753 ± 0.013M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 16 3.706 ± 0.018M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 20 3.660 ± 0.015M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 24 3.610 ± 0.016M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 28 3.238 ± 0.010M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 32 3.270 ± 0.018M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 36 2.892 ± 0.021M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 40 2.995 ± 0.018M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 44 2.830 ± 0.019M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 48 2.877 ± 0.015M/s (drops 0.000 ± 0.000M/s) rb-prod nr_prod 52 2.814 ± 0.015M/s (drops 0.000 ± 0.000M/s)

Signed-off-by: Xu Kuohai xukuohai@huawei.com --- tools/testing/selftests/bpf/bench.c | 2 + .../selftests/bpf/benchs/bench_ringbufs.c | 95 +++++++++++++++++-- .../bpf/benchs/run_bench_ringbufs.sh | 4 + .../selftests/bpf/progs/ringbuf_bench.c | 10 ++ 4 files changed, 103 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/bpf/bench.c b/tools/testing/selftests/bpf/bench.c index bd29bb2e6cb5..a98063f6436a 100644 --- a/tools/testing/selftests/bpf/bench.c +++ b/tools/testing/selftests/bpf/bench.c @@ -541,6 +541,7 @@ extern const struct bench bench_trig_uretprobe_multi_nop5;

extern const struct bench bench_rb_libbpf; extern const struct bench bench_rb_custom; +extern const struct bench bench_rb_prod; extern const struct bench bench_pb_libbpf; extern const struct bench bench_pb_custom; extern const struct bench bench_bloom_lookup; @@ -617,6 +618,7 @@ static const struct bench *benchs[] = { /* ringbuf/perfbuf benchmarks */ &bench_rb_libbpf, &bench_rb_custom, + &bench_rb_prod, &bench_pb_libbpf, &bench_pb_custom, &bench_bloom_lookup, diff --git a/tools/testing/selftests/bpf/benchs/bench_ringbufs.c b/tools/testing/selftests/bpf/benchs/bench_ringbufs.c index e1ee979e6acc..6d58479fac91 100644 --- a/tools/testing/selftests/bpf/benchs/bench_ringbufs.c +++ b/tools/testing/selftests/bpf/benchs/bench_ringbufs.c @@ -19,6 +19,7 @@ static struct { int ringbuf_sz; /* per-ringbuf, in bytes */ bool ringbuf_use_output; /* use slower output API */ int perfbuf_sz; /* per-CPU size, in pages */ + bool overwrite; } args = { .back2back = false, .batch_cnt = 500, @@ -27,6 +28,7 @@ static struct { .ringbuf_sz = 512 * 1024, .ringbuf_use_output = false, .perfbuf_sz = 128, + .overwrite = false, };

enum { @@ -35,6 +37,7 @@ enum { ARG_RB_BATCH_CNT = 2002, ARG_RB_SAMPLED = 2003, ARG_RB_SAMPLE_RATE = 2004, + ARG_RB_OVERWRITE = 2005, };

static const struct argp_option opts[] = { @@ -43,6 +46,7 @@ static const struct argp_option opts[] = { { "rb-batch-cnt", ARG_RB_BATCH_CNT, "CNT", 0, "Set BPF-side record batch count"}, { "rb-sampled", ARG_RB_SAMPLED, NULL, 0, "Notification sampling"}, { "rb-sample-rate", ARG_RB_SAMPLE_RATE, "RATE", 0, "Notification sample rate"}, + { "rb-overwrite", ARG_RB_OVERWRITE, NULL, 0, "Overwrite mode"}, {}, };

@@ -72,6 +76,9 @@ static error_t parse_arg(int key, char *arg, struct argp_state *state) argp_usage(state); } break; + case ARG_RB_OVERWRITE: + args.overwrite = true; + break; default: return ARGP_ERR_UNKNOWN; } @@ -95,8 +102,30 @@ static inline void bufs_trigger_batch(void)

static void bufs_validate(void) { - if (env.consumer_cnt != 1) { - fprintf(stderr, "rb-libbpf benchmark needs one consumer!\n"); + bool bench_prod = !strcmp(env.bench_name, "rb-prod"); + + if (args.overwrite && !bench_prod) { + fprintf(stderr, "overwite mode only works with benchmakr rb-prod!\n"); + exit(1); + } + + if (bench_prod && env.consumer_cnt != 0) { + fprintf(stderr, "rb-prod benchmark does not need consumer!\n"); + exit(1); + } + + if (bench_prod && args.back2back) { + fprintf(stderr, "back-to-back mode makes no sense for rb-prod!\n"); + exit(1); + } + + if (bench_prod && args.sampled) { + fprintf(stderr, "sampling mode makes no sense for rb-prod!\n"); + exit(1); + } + + if (!bench_prod && env.consumer_cnt != 1) { + fprintf(stderr, "benchmarks excluding rb-prod need one consumer!\n"); exit(1); }

@@ -132,8 +161,10 @@ static void ringbuf_libbpf_measure(struct bench_res *res) res->drops = atomic_swap(&ctx->skel->bss->dropped, 0); }

-static struct ringbuf_bench *ringbuf_setup_skeleton(void) +static struct ringbuf_bench *ringbuf_setup_skeleton(int bench_prod) { + __u32 flags; + struct bpf_map *ringbuf; struct ringbuf_bench *skel;

setup_libbpf(); @@ -146,12 +177,19 @@ static struct ringbuf_bench *ringbuf_setup_skeleton(void)

skel->rodata->batch_cnt = args.batch_cnt; skel->rodata->use_output = args.ringbuf_use_output ? 1 : 0; + skel->rodata->bench_prod = bench_prod;

if (args.sampled) /* record data + header take 16 bytes */ skel->rodata->wakeup_data_size = args.sample_rate * 16;

- bpf_map__set_max_entries(skel->maps.ringbuf, args.ringbuf_sz); + ringbuf = skel->maps.ringbuf; + if (args.overwrite) { + flags = bpf_map__map_flags(ringbuf) | BPF_F_OVERWRITE; + bpf_map__set_map_flags(ringbuf, flags); + } + + bpf_map__set_max_entries(ringbuf, args.ringbuf_sz);

if (ringbuf_bench__load(skel)) { fprintf(stderr, "failed to load skeleton\n"); @@ -171,10 +209,13 @@ static void ringbuf_libbpf_setup(void) { struct ringbuf_libbpf_ctx *ctx = &ringbuf_libbpf_ctx; struct bpf_link *link; + int map_fd;

- ctx->skel = ringbuf_setup_skeleton(); - ctx->ringbuf = ring_buffer__new(bpf_map__fd(ctx->skel->maps.ringbuf), - buf_process_sample, NULL, NULL); + ctx->skel = ringbuf_setup_skeleton(0); + + map_fd = bpf_map__fd(ctx->skel->maps.ringbuf); + ctx->ringbuf = ring_buffer__new(map_fd, buf_process_sample, + NULL, NULL); if (!ctx->ringbuf) { fprintf(stderr, "failed to create ringbuf\n"); exit(1); @@ -232,7 +273,7 @@ static void ringbuf_custom_setup(void) void *tmp; int err;

- ctx->skel = ringbuf_setup_skeleton(); + ctx->skel = ringbuf_setup_skeleton(0);

ctx->epoll_fd = epoll_create1(EPOLL_CLOEXEC); if (ctx->epoll_fd < 0) { @@ -277,6 +318,33 @@ static void ringbuf_custom_setup(void) } }

+/* RINGBUF-PRODUCER benchmark */ +static struct ringbuf_prod_ctx { + struct ringbuf_bench *skel; +} ringbuf_prod_ctx; + +static void ringbuf_prod_measure(struct bench_res *res) +{ + struct ringbuf_prod_ctx *ctx = &ringbuf_prod_ctx; + + res->hits = atomic_swap(&ctx->skel->bss->hits, 0); + res->drops = atomic_swap(&ctx->skel->bss->dropped, 0); +} + +static void ringbuf_prod_setup(void) +{ + struct ringbuf_prod_ctx *ctx = &ringbuf_prod_ctx; + struct bpf_link *link; + + ctx->skel = ringbuf_setup_skeleton(1); + + link = bpf_program__attach(ctx->skel->progs.bench_ringbuf); + if (!link) { + fprintf(stderr, "failed to attach program!\n"); + exit(1); + } +} + #define RINGBUF_BUSY_BIT (1 << 31) #define RINGBUF_DISCARD_BIT (1 << 30) #define RINGBUF_META_LEN 8 @@ -540,6 +608,17 @@ const struct bench bench_rb_custom = { .report_final = hits_drops_report_final, };

+const struct bench bench_rb_prod = { + .name = "rb-prod", + .argp = &bench_ringbufs_argp, + .validate = bufs_validate, + .setup = ringbuf_prod_setup, + .producer_thread = bufs_sample_producer, + .measure = ringbuf_prod_measure, + .report_progress = hits_drops_report_progress, + .report_final = hits_drops_report_final, +}; + const struct bench bench_pb_libbpf = { .name = "pb-libbpf", .argp = &bench_ringbufs_argp, diff --git a/tools/testing/selftests/bpf/benchs/run_bench_ringbufs.sh b/tools/testing/selftests/bpf/benchs/run_bench_ringbufs.sh index 91e3567962ff..84ae66beb0ec 100755 --- a/tools/testing/selftests/bpf/benchs/run_bench_ringbufs.sh +++ b/tools/testing/selftests/bpf/benchs/run_bench_ringbufs.sh @@ -49,3 +49,7 @@ for b in 1 2 3 4 8 12 16 20 24 28 32 36 40 44 48 52; do summarize "rb-libbpf nr_prod $b" "$($RUN_RB_BENCH -p$b --rb-batch-cnt 50 rb-libbpf)" done

+header "Ringbuf, overwrite mode with multi-producer contention, no consumer" +for b in 1 2 3 4 8 12 16 20 24 28 32 36 40 44 48 52; do + summarize "rb-prod nr_prod $b" "$($RUN_BENCH -p$b --rb-batch-cnt 50 --rb-overwrite rb-prod)" +done diff --git a/tools/testing/selftests/bpf/progs/ringbuf_bench.c b/tools/testing/selftests/bpf/progs/ringbuf_bench.c index 6a468496f539..c55282ba4038 100644 --- a/tools/testing/selftests/bpf/progs/ringbuf_bench.c +++ b/tools/testing/selftests/bpf/progs/ringbuf_bench.c @@ -14,9 +14,11 @@ struct {

const volatile int batch_cnt = 0; const volatile long use_output = 0; +const volatile long bench_prod = 0;

long sample_val = 42; long dropped __attribute__((aligned(128))) = 0; +long hits __attribute__((aligned(128))) = 0;

const volatile long wakeup_data_size = 0;

@@ -24,6 +26,9 @@ static __always_inline long get_flags() { long sz;

+ if (bench_prod) + return BPF_RB_NO_WAKEUP; + if (!wakeup_data_size) return 0;

@@ -47,6 +52,8 @@ int bench_ringbuf(void *ctx) *sample = sample_val; flags = get_flags(); bpf_ringbuf_submit(sample, flags); + if (bench_prod) + __sync_add_and_fetch(&hits, 1); } } } else { @@ -55,6 +62,9 @@ int bench_ringbuf(void *ctx) if (bpf_ringbuf_output(&ringbuf, &sample_val, sizeof(sample_val), flags)) __sync_add_and_fetch(&dropped, 1); + else if (bench_prod) + __sync_add_and_fetch(&hits, 1); + } } return 0;

-- 2.43.0

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Xu Kuohai