[src/trunk]: src/sys/kern Add a sysctl hashstat collector for bufhash.

[simonb <simonb%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/1f615abde42e
branches:  trunk
changeset: 960880:1f615abde42e
user:      simonb <simonb%NetBSD.org@localhost>
date:      Thu Apr 01 06:25:59 2021 +0000

description:
Add a sysctl hashstat collector for bufhash.

diffstat:

 sys/kern/vfs_bio.c |  41 +++++++++++++++++++++++++++++++++++++++--
 1 files changed, 39 insertions(+), 2 deletions(-)

diffs (76 lines):

diff -r 2906bd9ae554 -r 1f615abde42e sys/kern/vfs_bio.c
--- a/sys/kern/vfs_bio.c        Thu Apr 01 06:25:45 2021 +0000
+++ b/sys/kern/vfs_bio.c        Thu Apr 01 06:25:59 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: vfs_bio.c,v 1.297 2020/07/31 04:07:30 chs Exp $        */
+/*     $NetBSD: vfs_bio.c,v 1.298 2021/04/01 06:25:59 simonb Exp $     */
 
 /*-
  * Copyright (c) 2007, 2008, 2009, 2019, 2020 The NetBSD Foundation, Inc.
@@ -123,7 +123,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vfs_bio.c,v 1.297 2020/07/31 04:07:30 chs Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_bio.c,v 1.298 2021/04/01 06:25:59 simonb Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_bufcache.h"
@@ -252,6 +252,8 @@
 LIST_HEAD(bufhashhdr, buf) *bufhashtbl, invalhash;
 u_long bufhash;
 
+static int     bufhash_stats(struct hashstat_sysctl *, bool);
+
 static kcondvar_t needbuffer_cv;
 
 /*
@@ -536,6 +538,7 @@
 
        sysctl_kern_buf_setup();
        sysctl_vm_buf_setup();
+       hashstat_register("bufhash", bufhash_stats);
 }
 
 void
@@ -1953,6 +1956,40 @@
                       CTL_VM, CTL_CREATE, CTL_EOL);
 }
 
+static int
+bufhash_stats(struct hashstat_sysctl *hs, bool fill)
+{
+       buf_t *bp;
+       uint64_t chain;
+
+       strlcpy(hs->hash_name, "bufhash", sizeof(hs->hash_name));
+       strlcpy(hs->hash_desc, "buffer hash", sizeof(hs->hash_desc));
+       if (!fill)
+               return 0;
+
+       hs->hash_size = bufhash + 1;
+
+       for (size_t i = 0; i < hs->hash_size; i++) {
+               chain = 0;
+
+               mutex_enter(&bufcache_lock);
+               LIST_FOREACH(bp, &bufhashtbl[i], b_hash) {
+                       chain++;
+               }
+               mutex_exit(&bufcache_lock);
+
+               if (chain > 0) {
+                       hs->hash_used++;
+                       hs->hash_items += chain;
+                       if (chain > hs->hash_maxchain)
+                               hs->hash_maxchain = chain;
+               }
+               preempt_point();
+       }
+
+       return 0;
+}
+
 #ifdef DEBUG
 /*
  * Print out statistics on the current allocation of the buffer pool.