From 5c7fc2d27d004f28f3a94b35edd40e68f779e35a Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Wed, 25 Mar 2015 12:49:25 -0700 Subject: samples/bpf: Add IO latency analysis (iosnoop/heatmap) tool BPF C program attaches to blk_mq_start_request()/blk_update_request() kprobe events to calculate IO latency. For every completed block IO event it computes the time delta in nsec and records in a histogram map: map[log10(delta)*10]++ User space reads this histogram map every 2 seconds and prints it as a 'heatmap' using gray shades of text terminal. Black spaces have many events and white spaces have very few events. Left most space is the smallest latency, right most space is the largest latency in the range. Usage: $ sudo ./tracex3 and do 'sudo dd if=/dev/sda of=/dev/null' in other terminal. Observe IO latencies and how different activity (like 'make kernel') affects it. Similar experiments can be done for network transmit latencies, syscalls, etc. '-t' flag prints the heatmap using normal ascii characters: $ sudo ./tracex3 -t heatmap of IO latency # - many events with this latency - few events |1us |10us |100us |1ms |10ms |100ms |1s |10s *ooo. *O.#. # 221 . *# . # 125 .. .o#*.. # 55 . . . . .#O # 37 .# # 175 .#*. # 37 # # 199 . . *#*. # 55 *#..* # 42 # # 266 ...***Oo#*OO**o#* . # 629 # # 271 . .#o* o.*o* # 221 . . o* *#O.. # 50 Signed-off-by: Alexei Starovoitov Cc: Arnaldo Carvalho de Melo Cc: Arnaldo Carvalho de Melo Cc: Daniel Borkmann Cc: David S. Miller Cc: Jiri Olsa Cc: Linus Torvalds Cc: Masami Hiramatsu Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Peter Zijlstra Cc: Steven Rostedt Link: http://lkml.kernel.org/r/1427312966-8434-9-git-send-email-ast@plumgrid.com Signed-off-by: Ingo Molnar --- samples/bpf/Makefile | 4 ++ samples/bpf/tracex3_kern.c | 89 +++++++++++++++++++++++++++ samples/bpf/tracex3_user.c | 150 +++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 243 insertions(+) create mode 100644 samples/bpf/tracex3_kern.c create mode 100644 samples/bpf/tracex3_user.c (limited to 'samples/bpf') diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile index 6dd272143733..dcd850546d52 100644 --- a/samples/bpf/Makefile +++ b/samples/bpf/Makefile @@ -8,6 +8,7 @@ hostprogs-y += sockex1 hostprogs-y += sockex2 hostprogs-y += tracex1 hostprogs-y += tracex2 +hostprogs-y += tracex3 test_verifier-objs := test_verifier.o libbpf.o test_maps-objs := test_maps.o libbpf.o @@ -16,6 +17,7 @@ sockex1-objs := bpf_load.o libbpf.o sockex1_user.o sockex2-objs := bpf_load.o libbpf.o sockex2_user.o tracex1-objs := bpf_load.o libbpf.o tracex1_user.o tracex2-objs := bpf_load.o libbpf.o tracex2_user.o +tracex3-objs := bpf_load.o libbpf.o tracex3_user.o # Tell kbuild to always build the programs always := $(hostprogs-y) @@ -23,6 +25,7 @@ always += sockex1_kern.o always += sockex2_kern.o always += tracex1_kern.o always += tracex2_kern.o +always += tracex3_kern.o HOSTCFLAGS += -I$(objtree)/usr/include @@ -31,6 +34,7 @@ HOSTLOADLIBES_sockex1 += -lelf HOSTLOADLIBES_sockex2 += -lelf HOSTLOADLIBES_tracex1 += -lelf HOSTLOADLIBES_tracex2 += -lelf +HOSTLOADLIBES_tracex3 += -lelf # point this to your LLVM backend with bpf support LLC=$(srctree)/tools/bpf/llvm/bld/Debug+Asserts/bin/llc diff --git a/samples/bpf/tracex3_kern.c b/samples/bpf/tracex3_kern.c new file mode 100644 index 000000000000..255ff2792366 --- /dev/null +++ b/samples/bpf/tracex3_kern.c @@ -0,0 +1,89 @@ +/* Copyright (c) 2013-2015 PLUMgrid, http://plumgrid.com + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of version 2 of the GNU General Public + * License as published by the Free Software Foundation. + */ +#include +#include +#include +#include +#include "bpf_helpers.h" + +struct bpf_map_def SEC("maps") my_map = { + .type = BPF_MAP_TYPE_HASH, + .key_size = sizeof(long), + .value_size = sizeof(u64), + .max_entries = 4096, +}; + +/* kprobe is NOT a stable ABI. If kernel internals change this bpf+kprobe + * example will no longer be meaningful + */ +SEC("kprobe/blk_mq_start_request") +int bpf_prog1(struct pt_regs *ctx) +{ + long rq = ctx->di; + u64 val = bpf_ktime_get_ns(); + + bpf_map_update_elem(&my_map, &rq, &val, BPF_ANY); + return 0; +} + +static unsigned int log2l(unsigned long long n) +{ +#define S(k) if (n >= (1ull << k)) { i += k; n >>= k; } + int i = -(n == 0); + S(32); S(16); S(8); S(4); S(2); S(1); + return i; +#undef S +} + +#define SLOTS 100 + +struct bpf_map_def SEC("maps") lat_map = { + .type = BPF_MAP_TYPE_ARRAY, + .key_size = sizeof(u32), + .value_size = sizeof(u64), + .max_entries = SLOTS, +}; + +SEC("kprobe/blk_update_request") +int bpf_prog2(struct pt_regs *ctx) +{ + long rq = ctx->di; + u64 *value, l, base; + u32 index; + + value = bpf_map_lookup_elem(&my_map, &rq); + if (!value) + return 0; + + u64 cur_time = bpf_ktime_get_ns(); + u64 delta = cur_time - *value; + + bpf_map_delete_elem(&my_map, &rq); + + /* the lines below are computing index = log10(delta)*10 + * using integer arithmetic + * index = 29 ~ 1 usec + * index = 59 ~ 1 msec + * index = 89 ~ 1 sec + * index = 99 ~ 10sec or more + * log10(x)*10 = log2(x)*10/log2(10) = log2(x)*3 + */ + l = log2l(delta); + base = 1ll << l; + index = (l * 64 + (delta - base) * 64 / base) * 3 / 64; + + if (index >= SLOTS) + index = SLOTS - 1; + + value = bpf_map_lookup_elem(&lat_map, &index); + if (value) + __sync_fetch_and_add((long *)value, 1); + + return 0; +} +char _license[] SEC("license") = "GPL"; +u32 _version SEC("version") = LINUX_VERSION_CODE; diff --git a/samples/bpf/tracex3_user.c b/samples/bpf/tracex3_user.c new file mode 100644 index 000000000000..0aaa933ab938 --- /dev/null +++ b/samples/bpf/tracex3_user.c @@ -0,0 +1,150 @@ +/* Copyright (c) 2013-2015 PLUMgrid, http://plumgrid.com + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of version 2 of the GNU General Public + * License as published by the Free Software Foundation. + */ +#include +#include +#include +#include +#include +#include +#include +#include "libbpf.h" +#include "bpf_load.h" + +#define ARRAY_SIZE(x) (sizeof(x) / sizeof(*(x))) + +#define SLOTS 100 + +static void clear_stats(int fd) +{ + __u32 key; + __u64 value = 0; + + for (key = 0; key < SLOTS; key++) + bpf_update_elem(fd, &key, &value, BPF_ANY); +} + +const char *color[] = { + "\033[48;5;255m", + "\033[48;5;252m", + "\033[48;5;250m", + "\033[48;5;248m", + "\033[48;5;246m", + "\033[48;5;244m", + "\033[48;5;242m", + "\033[48;5;240m", + "\033[48;5;238m", + "\033[48;5;236m", + "\033[48;5;234m", + "\033[48;5;232m", +}; +const int num_colors = ARRAY_SIZE(color); + +const char nocolor[] = "\033[00m"; + +const char *sym[] = { + " ", + " ", + ".", + ".", + "*", + "*", + "o", + "o", + "O", + "O", + "#", + "#", +}; + +bool full_range = false; +bool text_only = false; + +static void print_banner(void) +{ + if (full_range) + printf("|1ns |10ns |100ns |1us |10us |100us" + " |1ms |10ms |100ms |1s |10s\n"); + else + printf("|1us |10us |100us |1ms |10ms " + "|100ms |1s |10s\n"); +} + +static void print_hist(int fd) +{ + __u32 key; + __u64 value; + __u64 cnt[SLOTS]; + __u64 max_cnt = 0; + __u64 total_events = 0; + + for (key = 0; key < SLOTS; key++) { + value = 0; + bpf_lookup_elem(fd, &key, &value); + cnt[key] = value; + total_events += value; + if (value > max_cnt) + max_cnt = value; + } + clear_stats(fd); + for (key = full_range ? 0 : 29; key < SLOTS; key++) { + int c = num_colors * cnt[key] / (max_cnt + 1); + + if (text_only) + printf("%s", sym[c]); + else + printf("%s %s", color[c], nocolor); + } + printf(" # %lld\n", total_events); +} + +int main(int ac, char **argv) +{ + char filename[256]; + int i; + + snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]); + + if (load_bpf_file(filename)) { + printf("%s", bpf_log_buf); + return 1; + } + + for (i = 1; i < ac; i++) { + if (strcmp(argv[i], "-a") == 0) { + full_range = true; + } else if (strcmp(argv[i], "-t") == 0) { + text_only = true; + } else if (strcmp(argv[i], "-h") == 0) { + printf("Usage:\n" + " -a display wider latency range\n" + " -t text only\n"); + return 1; + } + } + + printf(" heatmap of IO latency\n"); + if (text_only) + printf(" %s", sym[num_colors - 1]); + else + printf(" %s %s", color[num_colors - 1], nocolor); + printf(" - many events with this latency\n"); + + if (text_only) + printf(" %s", sym[0]); + else + printf(" %s %s", color[0], nocolor); + printf(" - few events\n"); + + for (i = 0; ; i++) { + if (i % 20 == 0) + print_banner(); + print_hist(map_fd[1]); + sleep(2); + } + + return 0; +} -- cgit v1.2.3