libbpf-tools/biotop：Add PID filter support

libbpf-tools/biotop.bpf.c

@@ -9,6 +9,8 @@
 #include "maps.bpf.h"
 #include "core_fixes.bpf.h"
 
+const volatile pid_t target_pid = 0;
+
 struct {
  __uint(type, BPF_MAP_TYPE_HASH);
  __uint(max_entries, 10240);
@@ -34,10 +36,18 @@ static __always_inline
 int trace_start(struct request *req)
 {
  struct who_t who = {};
+ __u64 pid_tgid;
+ __u32 pid;
 
  /* cache PID and comm by-req */
+ pid_tgid = bpf_get_current_pid_tgid();
+ pid = pid_tgid >> 32;
+
+ if (target_pid && target_pid != pid)
+ return 0;
+
  bpf_get_current_comm(&who.name, sizeof(who.name));
- who.pid = bpf_get_current_pid_tgid() >> 32;
+ who.pid = pid;
  bpf_map_update_elem(&whobyreq, &req, &who, 0);
 
  return 0;
@@ -66,11 +76,16 @@ int trace_done(struct request *req)
  struct gendisk *disk;
  struct who_t *whop;
  u64 delta_us;
+ u64 id = bpf_get_current_pid_tgid();
+ u32 pid = id >> 32;
+
+ if (target_pid && target_pid != pid)
+ goto cleanup;
 
  /* fetch timestamp and calculate delta */
  startp = bpf_map_lookup_elem(&start, &req);
  if (!startp)
- return 0; /* missed tracing issue */
+ goto cleanup; /* missed tracing issue */
 
  delta_us = (bpf_ktime_get_ns() - startp->ts) / 1000;
 
@@ -97,9 +112,9 @@ int trace_done(struct request *req)
  valp->io++;
  }
 
+cleanup:
  bpf_map_delete_elem(&start, &req);
  bpf_map_delete_elem(&whobyreq, &req);
-
  return 0;
 }
 

libbpf-tools/biotop.c

@@ -6,6 +6,7 @@
  *
  * Based on biotop(8) from BCC by Brendan Gregg.
  * 03-Mar-2022 Francis Laniel Created this.
+ * 23-Nov-2023 Pcheng Cui Add PID filter support.
  */
 #ifndef _GNU_SOURCE
 #define _GNU_SOURCE
@@ -83,6 +84,7 @@ static int output_rows = 20;
 static int sort_by = ALL;
 static int interval = 1;
 static int count = 99999999;
+static pid_t target_pid = 0;
 static bool verbose = false;
 
 const char *argp_program_version = "biotop 0.1";
@@ -91,24 +93,26 @@ const char *argp_program_bug_address =
 const char argp_program_doc[] =
 "Trace file reads/writes by process.\n"
 "\n"
-"USAGE: biotop [-h] [interval] [count]\n"
+"USAGE: biotop [-h] [interval] [count] [-p PID]\n"
 "\n"
 "EXAMPLES:\n"
 " biotop # file I/O top, refresh every 1s\n"
-" biotop 5 10 # 5s summaries, 10 times\n";
+" biotop 5 10 # 5s summaries, 10 times\n"
+" biotop -p 181 # only trace PID 1216\n";
 
 static const struct argp_option opts[] = {
  { "noclear", 'C', NULL, 0, "Don't clear the screen" },
  { "sort", 's', "SORT", 0, "Sort columns, default all [all, io, bytes, time]" },
  { "rows", 'r', "ROWS", 0, "Maximum rows to print, default 20" },
+ { "pid", 'p', "PID", 0, "Process ID to trace" },
  { "verbose", 'v', NULL, 0, "Verbose debug output" },
  { NULL, 'h', NULL, OPTION_HIDDEN, "Show the full help" },
  {},
 };
 
 static error_t parse_arg(int key, char *arg, struct argp_state *state)
 {
- long rows;
+ long rows, pid;
  static int pos_args;
 
  switch (key) {
@@ -140,6 +144,15 @@ static error_t parse_arg(int key, char *arg, struct argp_state *state)
  if (output_rows > OUTPUT_ROWS_LIMIT)
  output_rows = OUTPUT_ROWS_LIMIT;
  break;
+ case 'p':
+ errno = 0;
+ pid = strtol(arg, NULL, 10);
+ if (errno || pid <= 0) {
+ warn("Invalid PID: %s\n", arg);
+ argp_usage(state);
+ }
+ target_pid = pid;
+ break;
  case 'v':
  verbose = true;
  break;
@@ -409,6 +422,8 @@ int main(int argc, char **argv)
  return 1;
  }
 
+ obj->rodata->target_pid = target_pid;
+
  parse_disk_stat();
 
  ksyms = ksyms__load();