top: much faster cursor key navigation by avoiding process rescan

function                                             old     new   delta
handle_input                                         549     560     +11
top_main                                             889     891      +2

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

diff --git a/procps/top.c b/procps/top.c
index fc056621b362af76b63d0067a80f5163749dc60d..075c96c2792ec6e4ae99ca04e29f1d7d9dbd27e1 100644 (file)
--- a/procps/top.c
+++ b/procps/top.c
@@ -896,7 +896,8 @@ enum {
                | PSSCAN_PID
                | PSSCAN_SMAPS
                | PSSCAN_COMM,
-       EXIT_MASK = (unsigned)-1,
+       EXIT_MASK = 0,
+       NO_RESCAN_MASK = (unsigned)-1,
 };
 
 #if ENABLE_FEATURE_TOP_INTERACTIVE
@@ -934,7 +935,7 @@ static unsigned handle_input(unsigned scan_mask, unsigned interval)
                }
                if (c == KEYCODE_HOME) {
                        G_scroll_ofs = 0;
-                       break;
+                       goto normalize_ofs;
                }
                if (c == KEYCODE_END) {
                        G_scroll_ofs = ntop - G.lines / 2;
@@ -951,7 +952,7 @@ static unsigned handle_input(unsigned scan_mask, unsigned interval)
                                G_scroll_ofs = ntop - 1;
                        if (G_scroll_ofs < 0)
                                G_scroll_ofs = 0;
-                       break;
+                       return NO_RESCAN_MASK;
                }
 
                c |= 0x20; /* lowercase */
@@ -1156,6 +1157,7 @@ int top_main(int argc UNUSED_PARAM, char **argv)
 #endif
 
        while (scan_mask != EXIT_MASK) {
+               unsigned new_mask;
                procps_status_t *p = NULL;
 
                if (OPT_BATCH_MODE) {
@@ -1233,21 +1235,32 @@ int top_main(int argc UNUSED_PARAM, char **argv)
 #else
                        qsort(top, ntop, sizeof(top_status_t), (void*)(sort_function[0]));
 #endif
-                       display_process_list(G.lines, col);
                }
 #if ENABLE_FEATURE_TOPMEM
                else { /* TOPMEM */
                        qsort(topmem, ntop, sizeof(topmem_status_t), (void*)topmem_sort);
+               }
+#endif
+ IF_FEATURE_TOP_INTERACTIVE(display:)
+               IF_FEATURE_TOPMEM(if (scan_mask != TOPMEM_MASK)) {
+                       display_process_list(G.lines, col);
+               }
+#if ENABLE_FEATURE_TOPMEM
+               else { /* TOPMEM */
                        display_topmem_process_list(G.lines, col);
                }
 #endif
-               clearmems();
                if (iterations >= 0 && !--iterations)
                        break;
 #if !ENABLE_FEATURE_TOP_INTERACTIVE
+               clearmems();
                sleep(interval);
 #else
-               scan_mask = handle_input(scan_mask, interval);
+               new_mask = handle_input(scan_mask, interval);
+               if (new_mask == NO_RESCAN_MASK)
+                       goto display;
+               scan_mask = new_mask;
+               clearmems();
 #endif
        } /* end of "while (not Q)" */