The vfs.write_behind sysctl and related code support has been added to
allow changes to the filesystem's write_behind behavior. By the default the filesystem aggressively issues write_behind's. Three values may be specified for vfs.write_behind. 0 disables write_behind, 1 results in historical operation (agressive write_behind), and 2 is an experimental backed-off write_behind. The values of 0 and 1 are recommended. The value of 0 is recommended in conjuction with an increase in the number of NBUF's and the number of dirty buffers allowed (vfs.{lo,hi}dirtybuffers). Note that a value of 0 will radically increase the dirty buffer load on the system. Future work on write_behind behavior will use values 2 and greater for testing purposes. Submitted by: Matthew Dillon <dillon@apollo.backplane.com> Reviewed by: Kirk McKusick <mckusick@mckusick.com>
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parent
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Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=48545
@ -33,7 +33,7 @@
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* SUCH DAMAGE.
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*
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* @(#)vfs_cluster.c 8.7 (Berkeley) 2/13/94
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* $Id: vfs_cluster.c,v 1.84 1999/06/26 02:46:08 mckusick Exp $
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* $Id: vfs_cluster.c,v 1.85 1999/06/29 05:59:43 peter Exp $
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*/
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#include "opt_debug_cluster.h"
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@ -51,6 +51,7 @@
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#include <vm/vm_prot.h>
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#include <vm/vm_object.h>
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#include <vm/vm_page.h>
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#include <sys/sysctl.h>
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#if defined(CLUSTERDEBUG)
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#include <sys/sysctl.h>
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@ -66,6 +67,9 @@ static struct buf *
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cluster_rbuild __P((struct vnode *vp, u_quad_t filesize, daddr_t lbn,
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daddr_t blkno, long size, int run, struct buf *fbp));
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static int write_behind = 1;
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SYSCTL_INT(_vfs, OID_AUTO, write_behind, CTLFLAG_RW, &write_behind, 0, "");
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extern vm_page_t bogus_page;
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extern int cluster_pbuf_freecnt;
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@ -153,12 +157,14 @@ cluster_read(vp, filesize, lblkno, size, cred, totread, seqcount, bpp)
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(i == (maxra - 1)))
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tbp->b_flags |= B_RAM;
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#if 0
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if ((tbp->b_usecount < 1) &&
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BUF_REFCNT(tbp) == 0 &&
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(tbp->b_qindex == QUEUE_LRU)) {
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TAILQ_REMOVE(&bufqueues[QUEUE_LRU], tbp, b_freelist);
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TAILQ_INSERT_TAIL(&bufqueues[QUEUE_LRU], tbp, b_freelist);
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}
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#endif
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}
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splx(s);
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if (i >= maxra) {
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@ -494,6 +500,37 @@ cluster_callback(bp)
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relpbuf(bp, &cluster_pbuf_freecnt);
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}
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/*
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* cluster_wbuild_wb:
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*
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* Implement modified write build for cluster.
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*
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* write_behind = 0 write behind disabled
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* write_behind = 1 write behind normal (default)
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* write_behind = 2 write behind backed-off
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*/
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static __inline int
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cluster_wbuild_wb(struct vnode *vp, long size, daddr_t start_lbn, int len)
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{
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int r = 0;
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switch(write_behind) {
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case 2:
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if (start_lbn < len)
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break;
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start_lbn -= len;
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/* fall through */
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case 1:
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r = cluster_wbuild(vp, size, start_lbn, len);
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/* fall through */
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default:
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/* fall through */
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break;
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}
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return(r);
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}
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/*
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* Do clustered write for FFS.
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*
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@ -566,7 +603,7 @@ cluster_write(bp, filesize)
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bpp < endbp; bpp++)
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brelse(*bpp);
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free(buflist, M_SEGMENT);
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cluster_wbuild(vp, lblocksize,
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cluster_wbuild_wb(vp, lblocksize,
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vp->v_cstart, cursize);
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} else {
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/*
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@ -612,7 +649,7 @@ cluster_write(bp, filesize)
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* At end of cluster, write it out.
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*/
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bdwrite(bp);
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cluster_wbuild(vp, lblocksize, vp->v_cstart, vp->v_clen + 1);
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cluster_wbuild_wb(vp, lblocksize, vp->v_cstart, vp->v_clen + 1);
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vp->v_clen = 0;
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vp->v_cstart = lbn + 1;
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} else
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