Increase performance of atop utility on the systems with many threads.

atop-proclist-size.patch

--- atop-2.1.1/atop.c.orig	2014-09-06 17:12:52.000000000 +0400
+++ atop-2.1.1/atop.c	2016-12-20 18:57:25.733100314 +0300
@@ -299,7 +299,6 @@
 #include "parseable.h"
 
 #define	allflags  "ab:cde:fghijklmnopqrstuvwxyz1ABCDEFGHIJKL:MNOP:QRSTUVWXYZ"
-#define	PROCCHUNK	100	/* process-entries for future expansion  */
 #define	MAXFL		64      /* maximum number of command-line flags  */
 
 /*
@@ -733,7 +732,7 @@
 	presstat = calloc(1, sizeof(struct sstat));
 	devsstat = calloc(1, sizeof(struct sstat));
 
-	curtlen  = countprocs() * 3 / 2;	/* add 50% for threads */
+	curtlen  = countprocs() * 2;	/* increase twice for threads */
 	curtpres = calloc(curtlen, sizeof(struct tstat));
 
 	ptrverify(cursstat, "Malloc failed for current sysstats\n");
@@ -839,7 +838,7 @@
 
 		while ( (ntaskpres = photoproc(curtpres, curtlen)) == curtlen)
 		{
-			curtlen += PROCCHUNK;
+			curtlen *= 2;
 
 			curtpres = realloc(curtpres,
 					curtlen * sizeof(struct tstat));
--- atop-2.1.1/photoproc.c.orig	2014-09-06 17:12:52.000000000 +0400
+++ atop-2.1.1/photoproc.c	2016-12-20 21:53:30.890806203 +0300
@@ -373,7 +373,40 @@
 }
 
 /*
-** count number of processes currently running
+** count number of threads for given process
+*/
+unsigned int
+counttasks(const char *pid)
+{
+	unsigned int	nr = 0;
+	DIR		*dirp;
+	struct dirent	*entp;
+	char		origdir[1024];
+
+	if ( getcwd(origdir, sizeof origdir) == NULL)
+		cleanstop(53);
+
+	if ( chdir("/proc") == -1 || chdir(pid) == -1 || chdir("task") == -1)
+		cleanstop(53);
+
+	dirp = opendir(".");
+
+	while ( (entp = readdir(dirp)) )
+	{
+		if (isdigit(entp->d_name[0]))
+			nr++;
+	}
+
+	closedir(dirp);
+
+	if ( chdir(origdir) == -1)
+		cleanstop(53);
+
+	return nr ? nr : 1;
+}
+
+/*
+** count number of processes and threads currently running
 */
 unsigned int
 countprocs(void)
@@ -397,7 +430,7 @@
 		** count subdirectory-names starting with a digit
 		*/
 		if (isdigit(entp->d_name[0]))
-			nr++;
+			nr += counttasks(entp->d_name);
 	}
 
 	closedir(dirp);