On 1/31/23 3:05 AM, Anton Protopopov wrote:
On 23/01/30 04:22, Martin KaFai Lau wrote:
On 1/27/23 10:14 AM, Anton Protopopov wrote:
+/* The number of slots to store times */
+#define NR_SLOTS 32
+
+/* Configured by userspace */
+u64 nr_entries;
+u64 nr_loops;
+u32 __attribute__((__aligned__(8))) key[256];
+
+/* Filled by us */
+u64 __attribute__((__aligned__(256))) percpu_times_index[NR_SLOTS]; > +u64 __attribute__((__aligned__(256))) percpu_times[256][NR_SLOTS];
+
+static inline void patch_key(u32 i)
+{
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+ key[0] = i + 1;
+#else
+ key[0] = __builtin_bswap32(i + 1);
+#endif
+ /* the rest of key is random and is configured by userspace */
+}
+
+static int lookup_callback(__u32 index, u32 *unused)
+{
+ patch_key(index);
+ return bpf_map_lookup_elem(&hash_map_bench, key) ? 0 : 1;
+}
+
+static int loop_lookup_callback(__u32 index, u32 *unused)
+{
+ return bpf_loop(nr_entries, lookup_callback, NULL, 0) ? 0 : 1;
+}
+
+SEC("fentry/" SYS_PREFIX "sys_getpgid")
+int benchmark(void *ctx)
+{
+ u32 cpu = bpf_get_smp_processor_id();
+ u32 times_index;
+ u64 start_time;
+
+ times_index = percpu_times_index[cpu & 255] % NR_SLOTS;
percpu_times_index only has NR_SLOTS (32) elements?
Yes, the idea was the following. One measurement (bpf prog execution) takes
about 20-80 ms (depending on the key/map size). So in 2-3 seconds we can get
about NR_SLOTS elements. For me 32 looked like enough to get stats for this
benchmark. Do you think this is better to make the NR_SLOTS
bigger/configurable?
I thought percpu_times_index[] is the next slot to use for a particular cpu in
percpu_times[256][NR_SLOTS]. 256 is the max number of cpu supported? It is doing
"cpu" & 255 also. Should it be sized as percpu_times_index[256] instead then?
May be #define what 256 is here such that it can have a self describe name.
+ start_time = bpf_ktime_get_ns();
+ bpf_loop(nr_loops, loop_lookup_callback, NULL, 0);
+ percpu_times[cpu & 255][times_index] = bpf_ktime_get_ns() - start_time;
+ percpu_times_index[cpu & 255] += 1;
+ return 0;
+}
