Commit d0551261 authored by Dmitrii Banshchikov's avatar Dmitrii Banshchikov Committed by Daniel Borkmann
Browse files

bpf: Add bpf_ktime_get_coarse_ns helper 



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: default avatarDmitrii Banshchikov <me@ubique.spb.ru>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarMartin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20201117184549.257280-1-me@ubique.spb.ru
parent ea87ae85

include/linux/bpf.h

+1 −0
Original line number Diff line number Diff line
@@ -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);

include/uapi/linux/bpf.h

+11 −0
Original line number Diff line number Diff line
@@ -3797,6 +3797,16 @@ union bpf_attr { 
 *		is cleared if the flag is not specified.

 *	Return

 *		**-EINVAL** if invalid *flags* are passed, zero otherwise.

 *

 * 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),			\
@@ -3959,6 +3969,7 @@ union bpf_attr { 
	FN(task_storage_delete),	\

	FN(get_current_task_btf),	\

	FN(bprm_opts_set),		\

	FN(ktime_get_coarse_ns),	\

	/* */



/* integer value in 'imm' field of BPF_CALL instruction selects which helper

kernel/bpf/core.c

+1 −0
Original line number Diff line number Diff line
@@ -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;

kernel/bpf/helpers.c

+13 −0
Original line number Diff line number Diff line
@@ -167,6 +167,17 @@ const struct bpf_func_proto bpf_ktime_get_boot_ns_proto = { 
	.ret_type	= RET_INTEGER,

};



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,

};



BPF_CALL_0(bpf_get_current_pid_tgid)

{

	struct task_struct *task = current;
@@ -685,6 +696,8 @@ bpf_base_func_proto(enum bpf_func_id func_id) 
		return &bpf_ktime_get_ns_proto;

	case BPF_FUNC_ktime_get_boot_ns:

		return &bpf_ktime_get_boot_ns_proto;

	case BPF_FUNC_ktime_get_coarse_ns:

		return &bpf_ktime_get_coarse_ns_proto;

	case BPF_FUNC_ringbuf_output:

		return &bpf_ringbuf_output_proto;

	case BPF_FUNC_ringbuf_reserve:

kernel/trace/bpf_trace.c

+2 −0
Original line number Diff line number Diff line
@@ -1280,6 +1280,8 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) 
		return &bpf_ktime_get_ns_proto;

	case BPF_FUNC_ktime_get_boot_ns:

		return &bpf_ktime_get_boot_ns_proto;

	case BPF_FUNC_ktime_get_coarse_ns:

		return &bpf_ktime_get_coarse_ns_proto;

	case BPF_FUNC_tail_call:

		return &bpf_tail_call_proto;

	case BPF_FUNC_get_current_pid_tgid:

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