Date: Mon, 24 Mar 2003 08:23:48 -0800 From: Wes Peters <wes@softweyr.com> To: freebsd-arch@freebsd.org Subject: Patch to protect process from pageout killing Message-ID: <200303240823.48262.wes@softweyr.com>
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As promised, here's the patch to protect a process from being killed when
pageout is in memory shortage. This allows a process to specify that it
is important enough to be skipped when pageout is looking for the largest
process to kill.
My needs are simple. We make a box that is a web proxy and runs from a
memory disk, using flash for permanent storage. The flash is mounted
only when a configuration write is needed, the box runs from the memory
disk. We've experienced a problem at certain customer sites where bind
will consume a lot (~30 MB) of ram and then pageout will kill the largest
process, which is usually either named or squid. This pretty much kills
the box. We'd much rather have pageout kill off some of the squid worker
processes, we can recover from that.
Is this a good approach to the problem? Feedback welcome.
--- kern/kern_resource.c.orig Sun Mar 23 22:12:55 2003
+++ kern/kern_resource.c Sun Mar 23 22:14:17 2003
@@ -562,12 +562,12 @@
}
switch (which) {
-
case RLIMIT_CPU:
mtx_lock_spin(&sched_lock);
p->p_cpulimit = limp->rlim_cur;
mtx_unlock_spin(&sched_lock);
break;
+
case RLIMIT_DATA:
if (limp->rlim_cur > maxdsiz)
limp->rlim_cur = maxdsiz;
@@ -625,6 +625,15 @@
if (limp->rlim_max < 1)
limp->rlim_max = 1;
break;
+
+ case RLIMIT_PROTECT:
+ mtx_lock_spin(&sched_lock);
+ if (limp->rlim_cur)
+ p->p_flag |= P_PROTECTED;
+ else
+ p->p_flag &= ~P_PROTECTED;
+ mtx_unlock_spin(&sched_lock);
+ break;
}
*alimp = *limp;
return (0);
--- sys/proc.h.orig Sun Mar 23 21:36:13 2003
+++ sys/proc.h Sun Mar 23 21:37:56 2003
@@ -629,6 +629,7 @@
#define P_EXEC 0x04000 /* Process called exec. */
#define P_THREADED 0x08000 /* Process is using threads. */
#define P_CONTINUED 0x10000 /* Proc has continued from a stopped state.
*/
+#define P_PROTECTED 0x20000 /* Do not kill on memory overcommit. */
/* flags that control how threads may be suspended for some reason */
#define P_STOPPED_SIG 0x20000 /* Stopped due to SIGSTOP/SIGTSTP */
--- sys/resource.h.orig Sun Mar 23 22:07:50 2003
+++ sys/resource.h Sun Mar 23 22:09:45 2003
@@ -92,8 +92,9 @@
#define RLIMIT_NOFILE 8 /* number of open files */
#define RLIMIT_SBSIZE 9 /* maximum size of all socket buffers */
#define RLIMIT_VMEM 10 /* virtual process size (inclusive of mmap) */
+#define RLIMIT_PROTECT 11 /* protect process from overcommit kill */
-#define RLIM_NLIMITS 11 /* number of resource limits */
+#define RLIM_NLIMITS 12 /* number of resource limits */
#define RLIM_INFINITY ((rlim_t)(((u_quad_t)1 << 63) - 1))
@@ -115,6 +116,7 @@
"nofile",
"sbsize",
"vmem",
+ "protect",
};
#endif
--- vm/vm_pageout.c.orig Sun Mar 23 21:38:19 2003
+++ vm/vm_pageout.c Sun Mar 23 21:40:15 2003
@@ -1184,9 +1184,10 @@
if (PROC_TRYLOCK(p) == 0)
continue;
/*
- * if this is a system process, skip it
+ * If this is a system or protected process, skip it.
*/
if ((p->p_flag & P_SYSTEM) || (p->p_pid == 1) ||
+ (p->p_flag & P_PROTECTED) ||
((p->p_pid < 48) && (vm_swap_size != 0))) {
PROC_UNLOCK(p);
continue;
--
Where am I, and what am I doing in this handbasket?
Wes Peters wes@softweyr.com
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