Add a generic Proportional Integral Derivative (PID) controller algorithm and

use it to regulate page daemon output.

This provides much smoother and more responsive page daemon output, anticipating
demand and avoiding pageout stalls by increasing the number of pages to match
the workload.  This is a reimplementation of work done by myself and mlaier at
Isilon.

Reviewed by:	bsdimp
Tested by:	pho
Sponsored by:	Netflix, Dell/EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D14402

1 files changed, 7 insertions, 0 deletions

diff --git a/sys/vm/vm_pagequeue.h b/sys/vm/vm_pagequeue.h
index 3e3654cb0cfc..6380ccb22da1 100644
--- a/sys/vm/vm_pagequeue.h
+++ b/sys/vm/vm_pagequeue.h
@@ -73,6 +73,8 @@ struct vm_pagequeue {
 	const char	* const pq_name;
 } __aligned(CACHE_LINE_SIZE);
 
+#include <sys/pidctrl.h>
+struct sysctl_oid;
 
 struct vm_domain {
 	struct vm_pagequeue vmd_pagequeues[PQ_COUNT];
@@ -83,6 +85,7 @@ struct vm_domain {
 	long vmd_segs;			/* bitmask of the segments */
 
 	/* Paging control variables, locked by domain_free_mtx. */
+	struct pidctrl vmd_pid;		/* Pageout controller. */
 	u_int vmd_free_count;
 	boolean_t vmd_oom;
 	int vmd_oom_seq;
@@ -113,6 +116,10 @@ struct vm_domain {
 	u_int vmd_pageout_wakeup_thresh;/* (c) min pages to wake pagedaemon */
 	u_int vmd_interrupt_free_min;	/* (c) reserved pages for int code */
 	u_int vmd_free_severe;		/* (c) severe page depletion point */
+
+	/* Name for sysctl etc. */
+	struct sysctl_oid *vmd_oid;
+	char vmd_name[sizeof(__XSTRING(MAXMEMDOM))];
 } __aligned(CACHE_LINE_SIZE);
 
 extern struct vm_domain vm_dom[MAXMEMDOM];