The helper uses CLOCK_MONOTONIC_COARSE source of time that is less
accurate but more performant.
We have a BPF CGROUP_SKB firewall that supports event logging through
bpf_perf_event_output(). Each event has a timestamp and currently we use
bpf_ktime_get_ns() for it. Use of bpf_ktime_get_coarse_ns() saves ~15-20
ns in time required for event logging.
bpf_ktime_get_ns():
EgressLogByRemoteEndpoint 113.82ns 8.79M
bpf_ktime_get_coarse_ns():
EgressLogByRemoteEndpoint 95.40ns 10.48M
Signed-off-by: Dmitrii Banshchikov <me@xxxxxxxxxxxxx>
---
include/linux/bpf.h | 1 +
include/uapi/linux/bpf.h | 9 +++++++++
kernel/bpf/core.c | 1 +
kernel/bpf/helpers.c | 13 +++++++++++++
kernel/trace/bpf_trace.c | 2 ++
tools/include/uapi/linux/bpf.h | 9 +++++++++
6 files changed, 35 insertions(+)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 581b2a2e78eb..e1bcb6d7345c 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1842,6 +1842,7 @@ extern const struct bpf_func_proto bpf_copy_from_user_proto;
extern const struct bpf_func_proto bpf_snprintf_btf_proto;
extern const struct bpf_func_proto bpf_per_cpu_ptr_proto;
extern const struct bpf_func_proto bpf_this_cpu_ptr_proto;
+extern const struct bpf_func_proto bpf_ktime_get_coarse_ns_proto;
const struct bpf_func_proto *bpf_tracing_func_proto(
enum bpf_func_id func_id, const struct bpf_prog *prog);
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 162999b12790..b637b68b10a9 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3787,6 +3787,14 @@ union bpf_attr {
* *ARG_PTR_TO_BTF_ID* of type *task_struct*.
* Return
* Pointer to the current task.
+ *
+ * u64 bpf_ktime_get_coarse_ns(void)
+ * Description
+ * Return a coarse-grained version of the time elapsed since system boot, in nanoseconds.
+ * Does not include time the system was suspended.
+ * See: **clock_gettime**\ (**CLOCK_MONOTONIC_COARSE**)
+ * Return
+ * Current *ktime*.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -3948,6 +3956,7 @@ union bpf_attr {
FN(task_storage_get), \
FN(task_storage_delete), \
FN(get_current_task_btf), \
+ FN(ktime_get_coarse_ns), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 55454d2278b1..ff55cbcfbab4 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2211,6 +2211,7 @@ const struct bpf_func_proto bpf_get_smp_processor_id_proto __weak;
const struct bpf_func_proto bpf_get_numa_node_id_proto __weak;
const struct bpf_func_proto bpf_ktime_get_ns_proto __weak;
const struct bpf_func_proto bpf_ktime_get_boot_ns_proto __weak;
+const struct bpf_func_proto bpf_ktime_get_coarse_ns_proto __weak;
const struct bpf_func_proto bpf_get_current_pid_tgid_proto __weak;
const struct bpf_func_proto bpf_get_current_uid_gid_proto __weak;
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 25520f5eeaf6..78e9bb968482 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -651,6 +651,17 @@ const struct bpf_func_proto bpf_this_cpu_ptr_proto = {
.arg1_type = ARG_PTR_TO_PERCPU_BTF_ID,
};
+BPF_CALL_0(bpf_ktime_get_coarse_ns)
+{
+ return ktime_get_coarse_ns();
+}
+
+const struct bpf_func_proto bpf_ktime_get_coarse_ns_proto = {
+ .func = bpf_ktime_get_coarse_ns,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+};
+
const struct bpf_func_proto bpf_get_current_task_proto __weak;
const struct bpf_func_proto bpf_probe_read_user_proto __weak;
const struct bpf_func_proto bpf_probe_read_user_str_proto __weak;
@@ -695,6 +706,8 @@ bpf_base_func_proto(enum bpf_func_id func_id)
return &bpf_ringbuf_discard_proto;
case BPF_FUNC_ringbuf_query:
return &bpf_ringbuf_query_proto;
+ case BPF_FUNC_ktime_get_coarse_ns:
+ return &bpf_ktime_get_coarse_ns_proto;
default:
break;
}
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 02986c7b90eb..c3b2222ab573 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1354,6 +1354,8 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_per_cpu_ptr_proto;
case BPF_FUNC_bpf_this_cpu_ptr:
return &bpf_this_cpu_ptr_proto;
+ case BPF_FUNC_ktime_get_coarse_ns:
+ return &bpf_ktime_get_coarse_ns_proto;
default:
return NULL;
}
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 162999b12790..b637b68b10a9 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -3787,6 +3787,14 @@ union bpf_attr {
* *ARG_PTR_TO_BTF_ID* of type *task_struct*.
* Return
* Pointer to the current task.
+ *
+ * u64 bpf_ktime_get_coarse_ns(void)
+ * Description
+ * Return a coarse-grained version of the time elapsed since system boot, in nanoseconds.
+ * Does not include time the system was suspended.
+ * See: **clock_gettime**\ (**CLOCK_MONOTONIC_COARSE**)
+ * Return
+ * Current *ktime*.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -3948,6 +3956,7 @@ union bpf_attr {
FN(task_storage_get), \
FN(task_storage_delete), \
FN(get_current_task_btf), \
+ FN(ktime_get_coarse_ns), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
--
2.24.1
