0b05a4e71

Denys Vlasenko

2025-08-06

SUCCESS Duration: 158s

Subject

top,pmap: speed up /smaps parsing

No binary (build failed)

Architecture: x86_64-linux-gnu Compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0

—

(log yok)

include/platform.h+3 -0

@@ -209,6 +209,8 @@
	# define SWAP_LE64(x) bb_bswap_64(x)
	# define IF_BIG_ENDIAN(...) __VA_ARGS__
	# define IF_LITTLE_ENDIAN(...)
+	/* How do bytes a,b,c,d (sequential in memory) look if fetched into uint32_t? */
+	# define PACK32_BYTES(a,b,c,d) (uint32_t)((d)+((c)<<8)+((b)<<16)+((a)<<24))
	#else
	# define SWAP_BE16(x) bswap_16(x)
	# define SWAP_BE32(x) bswap_32(x)
@@ -218,6 +220,7 @@
	# define SWAP_LE64(x) (x)
	# define IF_BIG_ENDIAN(...)
	# define IF_LITTLE_ENDIAN(...) __VA_ARGS__
+	# define PACK32_BYTES(a,b,c,d) (uint32_t)((a)+((b)<<8)+((c)<<16)+((d)<<24))
	#endif

libbb/procps.c+20 -13

@@ -195,7 +195,7 @@ static NOINLINE void procps_read_smaps(pid_t pid, procps_status_t *sp)

	FILE *file;
	char filename[sizeof("/proc/%u/smaps") + sizeof(int)*3];
-	char buf[PROCPS_BUFSIZE];
+	char buf[PROCPS_BUFSIZE] ALIGN4;

	sprintf(filename, "/proc/%u/smaps", (int)pid);

@@ -211,20 +211,27 @@ static NOINLINE void procps_read_smaps(pid_t pid, procps_status_t *sp)
	// .....

	char *tp;
-
-	if (buf[0] == 'S' \|\| buf[0] == 'P') {
+	#define bytes4 (uint32_t)buf
+	#define Priv PACK32_BYTES('P','r','i','v')
+	#define Shar PACK32_BYTES('S','h','a','r')
	#define SCAN(S, X) \
-	if (memcmp(buf, S, sizeof(S)-1) == 0) { \
-	tp = skip_whitespace(buf + sizeof(S)-1); \
-	sp->X += fast_strtoul_10(&tp); \
-	continue; \
-	}
-	SCAN("Private_Dirty:", private_dirty)
-	SCAN("Private_Clean:", private_clean)
-	SCAN("Shared_Dirty:" , shared_dirty )
-	SCAN("Shared_Clean:" , shared_clean )
-	#undef SCAN
+	if (memcmp(buf+4, S, sizeof(S)-1) == 0) { \
+	tp = skip_whitespace(buf+4 + sizeof(S)-1); \
+	sp->X += fast_strtoul_10(&tp); \
+	continue; \
+	}
+	if (bytes4 == Priv) {
+	SCAN("ate_Dirty:", private_dirty)
+	SCAN("ate_Clean:", private_clean)
+	}
+	if (bytes4 == Shar) {
+	SCAN("ed_Dirty:" , shared_dirty )
+	SCAN("ed_Clean:" , shared_clean )
	}
+	#undef bytes4
+	#undef Priv
+	#undef Shar
+	#undef SCAN
	tp = strchr(buf, '-');
	if (tp) {
	// We reached next mapping - the line of this form:

procps/pmap.c+26 -11

@@ -109,18 +109,33 @@ static int read_smaps(pid_t pid, char buf[PMAP_BUFSZ], struct smaprec *total)

	char tp, p;

-	if (buf[0] == 'S' \|\| buf[0] == 'P') {
+	#define bytes4 (uint32_t)buf
+	#define Pss_ PACK32_BYTES('P','s','s',':')
+	#define Swap PACK32_BYTES('S','w','a','p')
+	#define Priv PACK32_BYTES('P','r','i','v')
+	#define FETCH(X, N) \
+	tp = skip_whitespace(buf+4 + (N)); \
+	total->X += currec.X = fast_strtoul_10(&tp); \
+	continue
	#define SCAN(S, X) \
-	if (memcmp(buf, S, sizeof(S)-1) == 0) { \
-	tp = skip_whitespace(buf + sizeof(S)-1); \
-	total->X += currec.X = fast_strtoul_10(&tp); \
-	continue; \
-	}
-	SCAN("Pss:" , smap_pss );
-	SCAN("Swap:" , smap_swap );
-	SCAN("Private_Dirty:", private_dirty);
-	#undef SCAN
+	if (memcmp(buf+4, S, sizeof(S)-1) == 0) { \
+	FETCH(X, sizeof(S)-1); \
+	}
+	if (bytes4 == Pss_) {
+	FETCH(smap_pss, 0);
	}
+	if (bytes4 == Swap && buf[4] == ':') {
+	FETCH(smap_swap, 1);
+	}
+	if (bytes4 == Priv) {
+	SCAN("ate_Dirty:", private_dirty);
+	}
+	#undef bytes4
+	#undef Pss_
+	#undef Swap
+	#undef Priv
+	#undef FETCH
+	#undef SCAN
	tp = strchr(buf, '-');
	if (tp) {
	// We reached next mapping - the line of this form:
@@ -162,7 +177,7 @@ static int procps_get_maps(pid_t pid, unsigned opt)
	{
	struct smaprec total;
	int ret;
-	char buf[PMAP_BUFSZ];
+	char buf[PMAP_BUFSZ] ALIGN4;

	ret = read_cmdline(buf, sizeof(buf), pid, NULL);
	if (ret < 0)