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>

1 files changed, 19 insertions, 6 deletions

diff --git a/procps/top.c b/procps/top.c
index fc056621b..075c96c27 100644
--- 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)" */