Add Linux process column for context switches

Displays the incremental sum of voluntary_ctxt_switches and nonvoluntary_ctxt_switches.

htop.1.in

@@ -386,6 +386,9 @@ Which cgroup the process is in.
 .B OOM
 OOM killer score.
 .TP
+.B CTXT
+Incremental sum of voluntary and nonvoluntary context switches.
+.TP
 .B IO_PRIORITY (IO)
 The I/O scheduling class followed by the priority if the class supports it:
    \fBR\fR for Realtime

linux/LinuxProcess.c

@@ -107,6 +107,7 @@ ProcessFieldData Process_fields[] = {
    [M_PSS] = { .name = "M_PSS", .title = "  PSS ", .description = "proportional set size, same as M_RESIDENT but each page is divided by the number of processes sharing it.", .flags = PROCESS_FLAG_LINUX_SMAPS, },
    [M_SWAP] = { .name = "M_SWAP", .title = " SWAP ", .description = "Size of the process's swapped pages", .flags = PROCESS_FLAG_LINUX_SMAPS, },
    [M_PSSWP] = { .name = "M_PSSWP", .title = " PSSWP ", .description = "shows proportional swap share of this mapping, Unlike \"Swap\", this does not take into account swapped out page of underlying shmem objects.", .flags = PROCESS_FLAG_LINUX_SMAPS, },
+   [CTXT] = { .name = "CTXT", .title = " CTXT ", .description = "Context switches (incremental sum of voluntary_ctxt_switches and nonvoluntary_ctxt_switches)", .flags = PROCESS_FLAG_LINUX_CTXT, },
    [LAST_PROCESSFIELD] = { .name = "*** report bug! ***", .title = NULL, .description = NULL, .flags = 0, },
 };
 
@@ -276,6 +277,11 @@ void LinuxProcess_writeField(Process* this, RichString* str, ProcessField field)
    case PERCENT_IO_DELAY: LinuxProcess_printDelay(lp->blkio_delay_percent, buffer, n); break;
    case PERCENT_SWAP_DELAY: LinuxProcess_printDelay(lp->swapin_delay_percent, buffer, n); break;
    #endif
+   case CTXT:
+      if (lp->ctxt_diff > 1000)
+         attr |= A_BOLD;
+      xSnprintf(buffer, n, "%5lu ", lp->ctxt_diff);
+      break;
    default:
       Process_writeField((Process*)this, str, field);
       return;
@@ -359,6 +365,8 @@ long LinuxProcess_compare(const void* v1, const void* v2) {
    #endif
    case IO_PRIORITY:
       return LinuxProcess_effectiveIOPriority(p1) - LinuxProcess_effectiveIOPriority(p2);
+   case CTXT:
+      return ((long)p2->ctxt_diff - (long)p1->ctxt_diff);
    default:
       return Process_compare(v1, v2);
    }

linux/LinuxProcess.h

@@ -14,6 +14,7 @@ in the source distribution for its full text.
 #define PROCESS_FLAG_LINUX_CGROUP   0x0800
 #define PROCESS_FLAG_LINUX_OOM      0x1000
 #define PROCESS_FLAG_LINUX_SMAPS    0x2000
+#define PROCESS_FLAG_LINUX_CTXT     0x4000
 
 typedef enum UnsupportedProcessFields {
    FLAGS = 9,
@@ -80,7 +81,8 @@ typedef enum LinuxProcessFields {
    M_PSS = 119,
    M_SWAP = 120,
    M_PSSWP = 121,
-   LAST_PROCESSFIELD = 122,
+   CTXT = 122,
+   LAST_PROCESSFIELD = 123,
 } LinuxProcessField;
 
 #include "IOPriority.h"
@@ -138,6 +140,8 @@ typedef struct LinuxProcess_ {
    float blkio_delay_percent;
    float swapin_delay_percent;
    #endif
+   unsigned long ctxt_total;
+   unsigned long ctxt_diff;
 } LinuxProcess;
 
 #define Process_isKernelThread(_process) (((LinuxProcess*)(_process))->isKernelThread)

linux/LinuxProcessList.c

@@ -588,6 +588,32 @@ static void LinuxProcessList_readOomData(LinuxProcess* process, const char* dirn
    fclose(file);
 }
 
+static void LinuxProcessList_readCtxtData(LinuxProcess* process, const char* dirname, const char* name) {
+   char filename[MAX_NAME+1];
+   xSnprintf(filename, MAX_NAME, "%s/%s/status", dirname, name);
+   FILE* file = fopen(filename, "r");
+   if (!file)
+      return;
+   char buffer[PROC_LINE_LENGTH + 1];
+   unsigned long ctxt = 0;
+   while (fgets(buffer, PROC_LINE_LENGTH, file)) {
+      if (String_startsWith(buffer, "voluntary_ctxt_switches:")) {
+         unsigned long vctxt;
+         int ok = sscanf(buffer, "voluntary_ctxt_switches:\t%lu", &vctxt);
+         if (ok >= 1)
+            ctxt += vctxt;
+      } else if (String_startsWith(buffer, "nonvoluntary_ctxt_switches:")) {
+         unsigned long nvctxt;
+         int ok = sscanf(buffer, "nonvoluntary_ctxt_switches:\t%lu", &nvctxt);
+         if (ok >= 1)
+            ctxt += nvctxt;
+      }
+   }
+   fclose(file);
+   process->ctxt_diff = (ctxt > process->ctxt_total) ? (ctxt - process->ctxt_total) : 0;
+   process->ctxt_total = ctxt;
+}
+
 #ifdef HAVE_DELAYACCT
 
 static int handleNetlinkMsg(struct nl_msg *nlmsg, void *linuxProcess) {
@@ -885,6 +911,9 @@ static bool LinuxProcessList_recurseProcTree(LinuxProcessList* this, const char*
       if (settings->flags & PROCESS_FLAG_LINUX_OOM)
          LinuxProcessList_readOomData(lp, dirname, name);
 
+      if (settings->flags & PROCESS_FLAG_LINUX_CTXT)
+         LinuxProcessList_readCtxtData(lp, dirname, name);
+
       if (proc->state == 'Z' && (proc->basenameOffset == 0)) {
          proc->basenameOffset = -1;
          setCommand(proc, command, commLen);