Allocate pager bufs from UMA instead of 80-ish mutex protected linked list.

o In vm_pager_bufferinit() create pbuf_zone and start accounting on how many
  pbufs are we going to have set.
  In various subsystems that are going to utilize pbufs create private zones
  via call to pbuf_zsecond_create(). The latter calls uma_zsecond_create(),
  and sets a limit on created zone. After startup preallocate pbufs according
  to requirements of all pbuf zones.

  Subsystems that used to have a private limit with old allocator now have
  private pbuf zones: md(4), fusefs, NFS client, smbfs, VFS cluster, FFS,
  swap, vnode pager.

  The following subsystems use shared pbuf zone: cam(4), nvme(4), physio(9),
  aio(4). They should have their private limits, but changing that is out of
  scope of this commit.

o Fetch tunable value of kern.nswbuf from init_param2() and while here move
  NSWBUF_MIN to opt_param.h and eliminate opt_swap.h, that was holding only
  this option.
  Default values aren't touched by this commit, but they probably should be
  reviewed wrt to modern hardware.

This change removes a tight bottleneck from sendfile(2) operation, that
uses pbufs in vnode pager. Other pagers also would benefit from faster
allocation.

Together with:	gallatin
Tested by:	pho

1 files changed, 0 insertions, 16 deletions

diff --git a/sys/kern/vfs_bio.c b/sys/kern/vfs_bio.c
index 2f0f3a637f7e..3766c7d8d55f 100644
--- a/sys/kern/vfs_bio.c
+++ b/sys/kern/vfs_bio.c
@@ -86,7 +86,6 @@ __FBSDID("$FreeBSD$");
 #include <vm/vm_extern.h>
 #include <vm/vm_map.h>
 #include <vm/swap_pager.h>
-#include "opt_swap.h"
 
 static MALLOC_DEFINE(M_BIOBUF, "biobuf", "BIO buffer");
 
@@ -1017,10 +1016,6 @@ bd_speedup(void)
 	mtx_unlock(&bdlock);
 }
 
-#ifndef NSWBUF_MIN
-#define	NSWBUF_MIN	16
-#endif
-
 #ifdef __i386__
 #define	TRANSIENT_DENOM	5
 #else
@@ -1130,19 +1125,8 @@ kern_vfs_bio_buffer_alloc(caddr_t v, long physmem_est)
 	}
 
 	/*
-	 * swbufs are used as temporary holders for I/O, such as paging I/O.
-	 * We have no less then 16 and no more then 256.
-	 */
-	nswbuf = min(nbuf / 4, 256);
-	TUNABLE_INT_FETCH("kern.nswbuf", &nswbuf);
-	if (nswbuf < NSWBUF_MIN)
-		nswbuf = NSWBUF_MIN;
-
-	/*
 	 * Reserve space for the buffer cache buffers
 	 */
-	swbuf = (void *)v;
-	v = (caddr_t)(swbuf + nswbuf);
 	buf = (void *)v;
 	v = (caddr_t)(buf + nbuf);