linux: add ppid cache

src/process_iterator_linux.c

@@ -35,6 +35,17 @@
 #include <errno.h>
 #include <ctype.h>
 #include <time.h>
+#include <stdlib.h>
+#include "uthash.h"
+
+struct ppid_info
+{
+	pid_t pid;
+	pid_t ppid;
+	UT_hash_handle hh;
+};
+
+struct ppid_info *ppid_cache = NULL;
 
 static int check_proc(void)
 {
@@ -46,21 +57,40 @@ static int check_proc(void)
 	return 1;
 }
 
-int init_process_iterator(struct process_iterator *it, struct process_filter *filter)
+static int is_numeric(const char *str)
 {
-	if (!check_proc())
+	for (; *str != '\0' && isdigit(*str); str++)
+		;
+	return *str == '\0';
+}
+
+static void update_ppid_cache(struct process *p)
+{
+	struct ppid_info *pi;
+	pid_t pid = p->pid;
+	HASH_FIND(hh, ppid_cache, &pid, sizeof(pid_t), pi);
+	if (pi != NULL)
 	{
-		fprintf(stderr, "procfs is not mounted!\nAborting\n");
-		exit(-2);
+		pi->ppid = p->ppid;
 	}
-	/* open a directory stream to /proc directory */
-	if ((it->dip = opendir("/proc")) == NULL)
+	else
 	{
-		perror("opendir");
-		return -1;
+		pi = (struct ppid_info *)malloc(sizeof(struct ppid_info));
+		pi->pid = p->pid;
+		pi->ppid = p->ppid;
+		HASH_ADD(hh, ppid_cache, pid, sizeof(pid_t), pi);
+	}
+}
+
+static void delete_from_ppid_cache(pid_t pid)
+{
+	struct ppid_info *pi;
+	HASH_FIND(hh, ppid_cache, &pid, sizeof(pid_t), pi);
+	if (pi != NULL)
+	{
+		HASH_DEL(ppid_cache, pi);
+		free(pi);
 	}
-	it->filter = filter;
-	return 0;
 }
 
 static int read_process_info(pid_t pid, struct process *p)
@@ -74,48 +104,62 @@ static int read_process_info(pid_t pid, struct process *p)
 
 	p->pid = pid;
 
-	/* read command line */
-	sprintf(exefile, "/proc/%ld/cmdline", (long)p->pid);
-	if ((fd = fopen(exefile, "r")) != NULL)
+	/* read stat file */
+	sprintf(statfile, "/proc/%ld/stat", (long)p->pid);
+	if ((fd = fopen(statfile, "r")) != NULL)
 	{
-		if (fgets(p->command, sizeof(p->command), fd) == NULL)
+		if (fscanf(fd, "%*d (%*[^)]) %c %ld %*d %*d %*d %*d %*d %*d %*d %*d %*d %lf %lf",
+				   &state, &ppid, &utime, &stime) == 4)
 		{
-			ret = -1;
+			p->ppid = (pid_t)ppid;
 		}
 		else
 		{
-			p->max_cmd_len = sizeof(p->command) - 1;
+			ret = -1;
+		}
+		if (ret == 0 && strchr("ZXx", state) != NULL)
+		{
+			ret = -1;
+		}
+		if (ret == 0)
+		{
+			if (sc_clk_tck < 0)
+			{
+				sc_clk_tck = (double)sysconf(_SC_CLK_TCK);
+			}
+			p->cputime = (utime + stime) * 1000.0 / sc_clk_tck;
 		}
 		fclose(fd);
+		if (ret != 0)
+		{
+			p->ppid = (pid_t)-1;
+		}
+		update_ppid_cache(p);
 	}
 	else
 	{
+		if (access(statfile, F_OK) != 0)
+		{
+			delete_from_ppid_cache(pid);
+		}
 		ret = -1;
 	}
-
 	if (ret != 0)
 	{
 		return ret;
 	}
 
-	/* read stat file */
-	sprintf(statfile, "/proc/%ld/stat", (long)p->pid);
-	if ((fd = fopen(statfile, "r")) != NULL)
+	/* read command line */
+	sprintf(exefile, "/proc/%ld/cmdline", (long)p->pid);
+	if ((fd = fopen(exefile, "r")) != NULL)
 	{
-		if (fscanf(fd, "%*d (%*[^)]) %c %ld %*d %*d %*d %*d %*d %*d %*d %*d %*d %lf %lf",
-				   &state, &ppid, &utime, &stime) != 4 ||
-			strchr("ZXx", state) != NULL)
+		if (fgets(p->command, sizeof(p->command), fd) == NULL)
 		{
 			ret = -1;
 		}
 		else
 		{
-			p->ppid = (pid_t)ppid;
-			if (sc_clk_tck < 0)
-			{
-				sc_clk_tck = (double)sysconf(_SC_CLK_TCK);
-			}
-			p->cputime = (utime + stime) * 1000.0 / sc_clk_tck;
+			p->max_cmd_len = sizeof(p->command) - 1;
 		}
 		fclose(fd);
 	}
@@ -127,21 +171,53 @@ static int read_process_info(pid_t pid, struct process *p)
 	return ret;
 }
 
-pid_t getppid_of(pid_t pid)
+static void clear_ppid_cache(void)
 {
-	char statfile[32];
-	FILE *fd;
-	long ppid = -1;
-	if (pid <= 0)
-		return (pid_t)(-1);
-	sprintf(statfile, "/proc/%ld/stat", (long)pid);
-	if ((fd = fopen(statfile, "r")) != NULL)
+	struct ppid_info *current_item, *tmp;
+	HASH_ITER(hh, ppid_cache, current_item, tmp)
 	{
-		if (fscanf(fd, "%*d (%*[^)]) %*c %ld", &ppid) != 1)
-			ppid = -1;
-		fclose(fd);
+		HASH_DEL(ppid_cache, current_item);
+		free(current_item);
+	}
+}
+
+static void init_ppid_cache(void)
+{
+	static int run = 1;
+	if (!run)
+		return;
+	atexit(&clear_ppid_cache);
+	run = 0;
+}
+
+int init_process_iterator(struct process_iterator *it, struct process_filter *filter)
+{
+	init_ppid_cache();
+	if (!check_proc())
+	{
+		fprintf(stderr, "procfs is not mounted!\nAborting\n");
+		exit(-2);
+	}
+	/* open a directory stream to /proc directory */
+	if ((it->dip = opendir("/proc")) == NULL)
+	{
+		perror("opendir");
+		return -1;
 	}
-	return (pid_t)ppid;
+	it->filter = filter;
+	return 0;
+}
+
+pid_t getppid_of(pid_t pid)
+{
+	struct ppid_info *pi;
+	struct process proc;
+	HASH_FIND(hh, ppid_cache, &pid, sizeof(pid_t), pi);
+	if (pi != NULL)
+		return pi->ppid;
+	if (read_process_info(pid, &proc) == 0)
+		return proc.ppid;
+	return (pid_t)-1;
 }
 
 static int get_start_time(pid_t pid, struct timespec *start_time)
@@ -186,13 +262,6 @@ int is_child_of(pid_t child_pid, pid_t parent_pid)
 	return 0;
 }
 
-static int is_numeric(const char *str)
-{
-	for (; *str != '\0' && isdigit(*str); str++)
-		;
-	return *str == '\0';
-}
-
 int get_next_process(struct process_iterator *it, struct process *p)
 {
 	struct dirent *dit = NULL;