Yonghong Song 908432ca84 bpf: add helper bpf_perf_event_read_value for perf event array map ... Hardware pmu counters are limited resources. When there are more pmu based perf events opened than available counters, kernel will multiplex these events so each event gets certain percentage (but not 100%) of the pmu time. In case that multiplexing happens, the number of samples or counter value will not reflect the case compared to no multiplexing. This makes comparison between different runs difficult. Typically, the number of samples or counter value should be normalized before comparing to other experiments. The typical normalization is done like: normalized_num_samples = num_samples * time_enabled / time_running normalized_counter_value = counter_value * time_enabled / time_running where time_enabled is the time enabled for event and time_running is the time running for event since last normalization. This patch adds helper bpf_perf_event_read_value for kprobed based perf event array map, to read perf counter and enabled/running time. The enabled/running time is accumulated since the perf event open. To achieve scaling factor between two bpf invocations, users can can use cpu_id as the key (which is typical for perf array usage model) to remember the previous value and do the calculation inside the bpf program. Signed-off-by: Yonghong Song <yhs@fb.com> Acked-by: Alexei Starovoitov <ast@fb.com> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: David S. Miller <davem@davemloft.net>		2017-10-07 23:05:57 +01:00
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arraymap.c	bpf: perf event change needed for subsequent bpf helpers	2017-10-07 23:05:57 +01:00
bpf_lru_list.c	bpf: lru: Lower the PERCPU_NR_SCANS from 16 to 4	2017-04-17 13:55:52 -04:00
bpf_lru_list.h	bpf: Only set node->ref = 1 if it has not been set	2017-09-01 09:57:39 -07:00
cgroup.c	bpf: introduce BPF_PROG_QUERY command	2017-10-04 16:05:05 -07:00
core.c	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net	2017-10-05 18:19:22 -07:00
devmap.c	bpf: devmap: pass on return value of bpf_map_precharge_memlock	2017-09-18 16:53:30 -07:00
hashtab.c	bpf: Only set node->ref = 1 if it has not been set	2017-09-01 09:57:39 -07:00
helpers.c	bpf: rename ARG_PTR_TO_STACK	2017-01-09 16:56:27 -05:00
inode.c	bpf: Implement show_options	2017-07-06 03:31:46 -04:00
lpm_trie.c	bpf: Optimize lpm trie delete	2017-09-25 14:37:54 -07:00
Makefile	bpf: sock_map fixes for !CONFIG_BPF_SYSCALL and !STREAM_PARSER	2017-08-16 15:34:13 -07:00
map_in_map.c	bpf: Add syscall lookup support for fd array and htab	2017-06-29 13:13:25 -04:00
map_in_map.h	bpf: Add syscall lookup support for fd array and htab	2017-06-29 13:13:25 -04:00
percpu_freelist.c	bpf: introduce percpu_freelist	2016-03-08 15:28:31 -05:00
percpu_freelist.h	bpf: introduce percpu_freelist	2016-03-08 15:28:31 -05:00
sockmap.c	bpf: rename bpf_compute_data_end into bpf_compute_data_pointers	2017-09-26 13:36:44 -07:00
stackmap.c	bpf: Allow selecting numa node during map creation	2017-08-19 21:35:43 -07:00
syscall.c	bpf: introduce BPF_PROG_QUERY command	2017-10-04 16:05:05 -07:00
tnum.c	bpf/verifier: track signed and unsigned min/max values	2017-08-08 17:51:34 -07:00
verifier.c	bpf: add helper bpf_perf_event_read_value for perf event array map	2017-10-07 23:05:57 +01:00