libbpf-tools/biotop：Add PID filter support

Author: Ting Zhang

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();