diff --git a/Makefile b/Makefile
index 1c07efd..2db7c33 100644
--- a/Makefile
+++ b/Makefile
@@ -150,6 +150,7 @@ UPROGS=\
 	$U/_wc\
 	$U/_zombie\
 	$U/_trace\
+	$U/_sysinfotest
 
 
 
diff --git a/kernel/defs.h b/kernel/defs.h
index 4b9bbc0..fa86032 100644
--- a/kernel/defs.h
+++ b/kernel/defs.h
@@ -63,6 +63,7 @@ void            ramdiskrw(struct buf*);
 void*           kalloc(void);
 void            kfree(void *);
 void            kinit(void);
+uint64          getfreemem(void);
 
 // log.c
 void            initlog(int, struct superblock*);
@@ -104,6 +105,7 @@ void            yield(void);
 int             either_copyout(int user_dst, uint64 dst, void *src, uint64 len);
 int             either_copyin(void *dst, int user_src, uint64 src, uint64 len);
 void            procdump(void);
+uint64          getnproc(void);
 
 // swtch.S
 void            swtch(struct context*, struct context*);
diff --git a/kernel/kalloc.c b/kernel/kalloc.c
index fa6a0ac..9d7565a 100644
--- a/kernel/kalloc.c
+++ b/kernel/kalloc.c
@@ -80,3 +80,20 @@ kalloc(void)
     memset((char*)r, 5, PGSIZE); // fill with junk
   return (void*)r;
 }
+
+uint64
+getfreemem(void)
+{
+  struct run *r;
+  uint64 n = 0;
+
+  acquire(&kmem.lock);
+  r = kmem.freelist;
+  while (r) {
+    ++n;
+    r = r->next;
+  }
+  release(&kmem.lock);
+
+  return n * PGSIZE;
+}
diff --git a/kernel/proc.c b/kernel/proc.c
index 3de92aa..222e664 100644
--- a/kernel/proc.c
+++ b/kernel/proc.c
@@ -694,3 +694,14 @@ procdump(void)
     printf("\n");
   }
 }
+
+uint64
+getnproc(void)
+{
+  uint64 n = 0;
+  struct proc *p;
+  for (p = proc; p < &proc[NPROC]; ++p) {
+    if (p->state != UNUSED) ++n;
+  }
+  return n;
+}
diff --git a/kernel/syscall.c b/kernel/syscall.c
index d554c45..be48ab7 100644
--- a/kernel/syscall.c
+++ b/kernel/syscall.c
@@ -105,6 +105,7 @@ extern uint64 sys_wait(void);
 extern uint64 sys_write(void);
 extern uint64 sys_uptime(void);
 extern uint64 sys_trace(void);
+extern uint64 sys_sysinfo(void);
 
 static uint64 (*syscalls[])(void) = {
 [SYS_fork]    sys_fork,
@@ -129,6 +130,7 @@ static uint64 (*syscalls[])(void) = {
 [SYS_mkdir]   sys_mkdir,
 [SYS_close]   sys_close,
 [SYS_trace]   sys_trace,
+[SYS_sysinfo] sys_sysinfo,
 };
 
 static char *syscall_list[23] = {
diff --git a/kernel/syscall.h b/kernel/syscall.h
index cc112b9..0dfedc7 100644
--- a/kernel/syscall.h
+++ b/kernel/syscall.h
@@ -21,3 +21,4 @@
 #define SYS_mkdir  20
 #define SYS_close  21
 #define SYS_trace  22
+#define SYS_sysinfo 23
diff --git a/kernel/sysproc.c b/kernel/sysproc.c
index 8de6712..2b3eb3a 100644
--- a/kernel/sysproc.c
+++ b/kernel/sysproc.c
@@ -6,6 +6,7 @@
 #include "memlayout.h"
 #include "spinlock.h"
 #include "proc.h"
+#include "sysinfo.h"
 
 uint64
 sys_exit(void)
@@ -108,3 +109,23 @@ sys_trace(void)
 
   return 0;
 }
+
+uint64
+sys_sysinfo(void)
+{
+  uint64 addr; // user virtual address, pointing to a struct sysinfo.
+
+  if (argaddr(0, &addr) < 0)
+    return -1;
+
+  struct proc *p = myproc();
+  struct sysinfo si;
+
+  si.freemem = getfreemem();
+  si.nproc = getnproc();
+
+  if (copyout(p->pagetable, addr, (char *)&si, sizeof(si)) < 0)
+    return -1;
+
+  return 0;
+}
diff --git a/user/user.h b/user/user.h
index fdeeefc..83fe38a 100644
--- a/user/user.h
+++ b/user/user.h
@@ -1,5 +1,6 @@
 struct stat;
 struct rtcdate;
+struct sysinfo;
 
 // system calls
 int fork(void);
@@ -24,6 +25,7 @@ char* sbrk(int);
 int sleep(int);
 int uptime(void);
 int trace(int);
+int sysinfo(struct sysinfo *);
 
 // ulib.c
 int stat(const char*, struct stat*);
diff --git a/user/usys.pl b/user/usys.pl
index 9c97b05..bc109fd 100755
--- a/user/usys.pl
+++ b/user/usys.pl
@@ -37,3 +37,4 @@ sub entry {
 entry("sleep");
 entry("uptime");
 entry("trace");
+entry("sysinfo");