top,pmap: speed up /smaps parsing

function                                             old     new   delta
procps_read_smaps                                    515     529     +14
procps_get_maps                                      685     665     -20
.rodata                                           105847  105820     -27
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/2 up/down: 14/-47)            Total: -33 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 20 insertions, 13 deletions

diff --git a/libbb/procps.c b/libbb/procps.c
index d512993e8..de640d29e 100644
--- a/libbb/procps.c
+++ b/libbb/procps.c
@@ -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: