Support a wider history counter in pmcstat(8) gmon output

pmcstat(8) contains an option to output sampling data in a gmon format
compatible with gprof(1). Currently, it uses the default histcounter,
which is an (unsigned short). With large sets of sampling data, it
is possible to overflow the maximum value provided by an (unsigned
short).

This change adds the -e argument to pmcstat. If -e and -g are both
specified, pmcstat will use a histcounter type of uint64_t.

Differential Revision:	https://reviews.freebsd.org/D4151
Reviewed by:	jhb, bjk
Approved by:	gnn (mentor)
MFC after:	1 month
Sponsored by:	Juniper Networks

usr.sbin/pmcstat/pmcpl_gprof.c

@@ -74,6 +74,14 @@ __FBSDID("$FreeBSD$");
 #include "pmcpl_callgraph.h"
 #include "pmcpl_gprof.h"
 
+typedef	uint64_t	WIDEHISTCOUNTER;
+
+#define	WIDEHISTCOUNTER_MAX		UINT64_MAX
+#define	HISTCOUNTER_MAX			USHRT_MAX
+#define	WIDEHISTCOUNTER_GMONTYPE	((int) 64)
+#define	HISTCOUNTER_GMONTYPE		((int) 0)
+static int hc_sz=0;
+
 /*
  * struct pmcstat_gmonfile tracks a given 'gmon.out' file.  These
  * files are mmap()'ed in as needed.
@@ -126,11 +134,13 @@ pmcstat_gmon_create_file(struct pmcstat_gmonfile *pgf,
 
 	gm.lpc = image->pi_start;
 	gm.hpc = image->pi_end;
-	gm.ncnt = (pgf->pgf_nbuckets * sizeof(HISTCOUNTER)) +
+	gm.ncnt = (pgf->pgf_nbuckets * hc_sz) + sizeof(struct gmonhdr);
-	    sizeof(struct gmonhdr);
 	gm.version = GMONVERSION;
 	gm.profrate = 0;		/* use ticks */
-	gm.histcounter_type = 0;	/* compatibility with moncontrol() */
+	if (args.pa_flags & FLAG_DO_WIDE_GPROF_HC)
+		gm.histcounter_type = WIDEHISTCOUNTER_GMONTYPE;
+	else
+		gm.histcounter_type = HISTCOUNTER_GMONTYPE;
 	gm.spare[0] = gm.spare[1] = 0;
 
 	/* Write out the gmon header */
@@ -400,6 +410,7 @@ pmcpl_gmon_process(struct pmcstat_process *pp, struct pmcstat_pmcrecord *pmcr,
 	struct pmcstat_gmonfile *pgf;
 	uintfptr_t bucket;
 	HISTCOUNTER *hc;
+	WIDEHISTCOUNTER *whc;
 	pmc_id_t pmcid;
 
 	(void) nsamples; (void) usermode; (void) cpu;
@@ -437,6 +448,14 @@ pmcpl_gmon_process(struct pmcstat_process *pp, struct pmcstat_pmcrecord *pmcr,
 	 */
 	pgf = pmcstat_image_find_gmonfile(image, pmcid);
 	if (pgf == NULL) {
+		if (hc_sz == 0) {
+			/* Determine the correct histcounter size. */
+			if (args.pa_flags & FLAG_DO_WIDE_GPROF_HC)
+				hc_sz = sizeof(WIDEHISTCOUNTER);
+			else
+				hc_sz = sizeof(HISTCOUNTER);
+		}
+
 		if ((pgf = calloc(1, sizeof(*pgf))) == NULL)
 			err(EX_OSERR, "ERROR:");
 
@@ -448,7 +467,7 @@ pmcpl_gmon_process(struct pmcstat_process *pp, struct pmcstat_pmcrecord *pmcr,
 		pgf->pgf_nbuckets = (image->pi_end - image->pi_start) /
 		    FUNCTION_ALIGNMENT;	/* see <machine/profile.h> */
 		pgf->pgf_ndatabytes = sizeof(struct gmonhdr) +
-		    pgf->pgf_nbuckets * sizeof(HISTCOUNTER);
+		    pgf->pgf_nbuckets * hc_sz;
 		pgf->pgf_nsamples = 0;
 		pgf->pgf_file = NULL;
 
@@ -474,14 +493,25 @@ pmcpl_gmon_process(struct pmcstat_process *pp, struct pmcstat_pmcrecord *pmcr,
 
 	assert(bucket < pgf->pgf_nbuckets);
 
-	hc = (HISTCOUNTER *) ((uintptr_t) pgf->pgf_gmondata +
+	if (args.pa_flags & FLAG_DO_WIDE_GPROF_HC) {
-	    sizeof(struct gmonhdr));
+		whc = (WIDEHISTCOUNTER *) ((uintptr_t) pgf->pgf_gmondata +
+		    sizeof(struct gmonhdr));
 
-	/* saturating add */
+		/* saturating add */
-	if (hc[bucket] < 0xFFFFU)  /* XXX tie this to sizeof(HISTCOUNTER) */
+		if (whc[bucket] < WIDEHISTCOUNTER_MAX)
-		hc[bucket]++;
+			whc[bucket]++;
-	else /* mark that an overflow occurred */
+		else /* mark that an overflow occurred */
-		pgf->pgf_overflow = 1;
+			pgf->pgf_overflow = 1;
+	} else {
+		hc = (HISTCOUNTER *) ((uintptr_t) pgf->pgf_gmondata +
+		    sizeof(struct gmonhdr));
+
+		/* saturating add */
+		if (hc[bucket] < HISTCOUNTER_MAX)
+			hc[bucket]++;
+		else /* mark that an overflow occurred */
+			pgf->pgf_overflow = 1;
+	}
 
 	pgf->pgf_nsamples++;
 }

usr.sbin/pmcstat/pmcstat.8

@@ -25,7 +25,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd May 27, 2015
+.Dd November 17, 2015
 .Dt PMCSTAT 8
 .Os
 .Sh NAME
@@ -49,6 +49,7 @@
 .Op Fl a Ar pathname
 .Op Fl c Ar cpu-spec
 .Op Fl d
+.Op Fl e
 .Op Fl f Ar pluginopt
 .Op Fl g
 .Op Fl k Ar kerneldir
@@ -260,6 +261,12 @@ The default is to measure events for the target process alone.
 .Fl P ,
 or
 .Fl S ) .
+.It Fl e
+Specify that the gprof profile files will use a wide history counter.
+These files are produced in a format compatible with
+.Xr gprof 1 .
+However, other tools that cannot fully parse a BSD-style
+gmon header might be unable to correctly parse these files.
 .It Fl f Ar pluginopt
 Pass option string to the active plugin.
 .br

usr.sbin/pmcstat/pmcstat.c

@@ -506,6 +506,7 @@ pmcstat_show_usage(void)
 	    "\t -a file\t print sampled PCs and callgraph to \"file\"\n"
 	    "\t -c cpu-list\t set cpus for subsequent system-wide PMCs\n"
 	    "\t -d\t\t (toggle) track descendants\n"
+	    "\t -e\t\t use wide history counter for gprof(1) output\n"
 	    "\t -f spec\t pass \"spec\" to as plugin option\n"
 	    "\t -g\t\t produce gprof(1) compatible profiles\n"
 	    "\t -k dir\t\t set the path to the kernel\n"
@@ -627,7 +628,7 @@ main(int argc, char **argv)
 	CPU_COPY(&rootmask, &cpumask);
 
 	while ((option = getopt(argc, argv,
-	    "CD:EF:G:M:NO:P:R:S:TWa:c:df:gk:l:m:n:o:p:qr:s:t:vw:z:")) != -1)
+	    "CD:EF:G:M:NO:P:R:S:TWa:c:def:gk:l:m:n:o:p:qr:s:t:vw:z:")) != -1)
 		switch (option) {
 		case 'a':	/* Annotate + callgraph */
 			args.pa_flags |= FLAG_DO_ANNOTATE;
@@ -668,6 +669,10 @@ main(int argc, char **argv)
 			args.pa_required |= FLAG_HAS_PROCESS_PMCS;
 			break;
 
+		case 'e':	/* wide gprof metrics */
+			args.pa_flags |= FLAG_DO_WIDE_GPROF_HC;
+			break;
+
 		case 'F':	/* produce a system-wide calltree */
 			args.pa_flags |= FLAG_DO_CALLGRAPHS;
 			args.pa_plugin = PMCSTAT_PL_CALLTREE;
@@ -1022,6 +1027,13 @@ main(int argc, char **argv)
 "ERROR: options -g/-G/-m/-T require sampling PMCs or -R to be specified."
 		    );
 
+	/* check if -e was specified without -g */
+	if ((args.pa_flags & FLAG_DO_WIDE_GPROF_HC) &&
+	    !(args.pa_flags & FLAG_DO_GPROF))
+		errx(EX_USAGE,
+"ERROR: option -e requires gprof mode to be specified."
+		    );
+
 	/* check if -O was spuriously specified */
 	if ((args.pa_flags & FLAG_HAS_OUTPUT_LOGFILE) &&
 	    (args.pa_required & FLAG_HAS_OUTPUT_LOGFILE) == 0)

usr.sbin/pmcstat/pmcstat.h

@@ -55,6 +55,7 @@
 #define	FLAG_DO_ANALYSIS		0x00020000	/* -g or -G or -m or -T */
 #define	FLAGS_HAS_CPUMASK		0x00040000	/* -c */
 #define	FLAG_HAS_DURATION		0x00080000	/* -l secs */
+#define	FLAG_DO_WIDE_GPROF_HC		0x00100000	/* -e */
 
 #define	DEFAULT_SAMPLE_COUNT		65536
 #define	DEFAULT_WAIT_INTERVAL		5.0