System call hacking stuff

451f323d · Silas Boyd-Wickizer · 8160fa28 · 451f323d
--- a/preadtest.cc
+++ b/preadtest.cc
@@ -14,12 +14,20 @@
 #define BSIZE 4096
 #define PSIZE (4*BSIZE)

-static int usekernlet;
+static int use_async;

 static char buf[BSIZE];

 struct ipcctl *ipcctl = (struct ipcctl*)KSHARED;

+struct {
+  u64 acount;
+  u64 atot;
+
+  u64 pcount;
+  u64 ptot;
+} stats;
+
 static msgid_t
 ipc_msg_alloc(void)
 {
@@ -70,7 +78,12 @@ kernlet_pread(int fd, size_t count, off_t off)
  struct ipcmsg *msg;
  msgid_t msgid;
  pageid_t pageid;
+  u64 t0, t1;

+  if (!use_async)
+    return;
+
+  t0 = rdtsc();
  msgid = ipc_msg_alloc();
  if (msgid == NULL_MSGID) {
    fprintf(2, "kernlet_pread: ipc_alloc_msg failed");
@@ -91,14 +104,20 @@ kernlet_pread(int fd, size_t count, off_t off)

  if (async(fd, count, off, msgid, pageid) != 0)
    die("kernlet");
+
+  t1 = rdtsc();
+  stats.acount++;
+  stats.atot += t1 - t0;
 }

 static ssize_t
 xpread(int fd, void *buf, size_t count, off_t off)
 {
  struct ipcmsg *msg;
+  u64 t0, t1;
  int msgid;

+  t0 = rdtsc();
  msgid = ipcctl->msgtail % IPC_NMSG;
  msg = &ipcctl->msg[msgid];

@@ -108,7 +127,7 @@ xpread(int fd, void *buf, size_t count, off_t off)
    if (msg->result == -1)
      die("xpread: result oops");
    if (msg->off != off)
-      die("xpread: off oops");
+      die("xpread: off oops %lu", off);

    char *kbuf = (char*) (KSHARED+PGSIZE+(msg->pageid*PGSIZE));
    off_t kbufoff = off - msg->off;
@@ -117,10 +136,17 @@ xpread(int fd, void *buf, size_t count, off_t off)
    memmove(buf, kbuf+kbufoff, kbufcount);
    ipc_msg_free(msgid);
    ipc_page_free(msg->pageid);
+    t1 = rdtsc();
+    stats.pcount++;
+    stats.ptot += t1 - t0;
    return kbufcount;
  }

-  return pread(fd, buf, count, off);
+  ssize_t r = pread(fd, buf, count, off);
+  t1 = rdtsc();
+  stats.pcount++;
+  stats.ptot += t1 - t0;
+  return r;
 }

 int
@@ -133,7 +159,7 @@ main(int ac, char **av)
  memset(ipcctl, 0, sizeof(*ipcctl));

  if (ac > 1)
-    usekernlet = av[1][0] == 'k';
+    use_async = av[1][0] == 'a';
  
  fd = open("preadtest.x", O_CREATE|O_RDWR);
  if (fd < 0)
@@ -144,16 +170,26 @@ main(int ac, char **av)
      die("write failed");

  t0 = rdtsc();
-  kernlet_pread(fd, BSIZE, 0);
+  kernlet_pread(fd, BSIZE, 0*BSIZE);
+  kernlet_pread(fd, BSIZE, 1*BSIZE);
+  kernlet_pread(fd, BSIZE, 2*BSIZE);
+  kernlet_pread(fd, BSIZE, 3*BSIZE);
+  kernlet_pread(fd, BSIZE, 4*BSIZE);
  for (i = 0; i < FSIZE; i+=BSIZE) {
    if (xpread(fd, buf, BSIZE, i) != BSIZE)
      die("pread failed");
-    kernlet_pread(fd, BSIZE, i+BSIZE);
+    if (i+BSIZE+3*BSIZE < FSIZE)
+      kernlet_pread(fd, BSIZE, i+BSIZE+4*BSIZE);
  }
  t1 = rdtsc();

-  fprintf(1, "usekernlet %u\n", usekernlet);  
-  fprintf(1, "cycles %lu\n", t1 - t0);
+  printf("use_async %u\n", use_async);  
+  printf("pread: count %lu total %lu ave %lu\n",
+         stats.pcount, stats.ptot, stats.ptot / stats.pcount);
+  if (use_async)
+    printf("async: count %lu total %lu ave %lu\n",
+           stats.acount, stats.atot, stats.atot / stats.acount);
+  printf("total %lu\n", t1 - t0);  

  exit();
 }