[src/trunk]: src/sys/miscfs/specfs When reading from a block device, queue pa...

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

details:   https://anonhg.NetBSD.org/src/rev/7edb7d83d24a
branches:  trunk
changeset: 948300:7edb7d83d24a
user:      mlelstv <mlelstv%NetBSD.org@localhost>
date:      Fri Dec 25 09:28:56 2020 +0000

description:
When reading from a block device, queue parallel block requests to
fill a buffer with breadn.

diffstat:

 sys/miscfs/specfs/spec_vnops.c |  41 ++++++++++++++++++++++++++++++++++++-----
 1 files changed, 36 insertions(+), 5 deletions(-)

diffs (78 lines):

diff -r 2138af3a1771 -r 7edb7d83d24a sys/miscfs/specfs/spec_vnops.c
--- a/sys/miscfs/specfs/spec_vnops.c    Fri Dec 25 09:02:41 2020 +0000
+++ b/sys/miscfs/specfs/spec_vnops.c    Fri Dec 25 09:28:56 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: spec_vnops.c,v 1.180 2020/06/27 17:29:19 christos Exp $        */
+/*     $NetBSD: spec_vnops.c,v 1.181 2020/12/25 09:28:56 mlelstv Exp $ */
 
 /*-
  * Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -58,7 +58,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: spec_vnops.c,v 1.180 2020/06/27 17:29:19 christos Exp $");
+__KERNEL_RCSID(0, "$NetBSD: spec_vnops.c,v 1.181 2020/12/25 09:28:56 mlelstv Exp $");
 
 #include <sys/param.h>
 #include <sys/proc.h>
@@ -695,6 +695,10 @@
        struct partinfo pi;
        int n, on;
        int error = 0;
+       int i, nra;
+       daddr_t lastbn, *rablks;
+       int *rasizes;
+       int nrablks, ratogo;
 
        KASSERT(uio->uio_rw == UIO_READ);
        KASSERTMSG(VMSPACE_IS_KERNEL_P(uio->uio_vmspace) ||
@@ -723,18 +727,45 @@
                        bsize = BLKDEV_IOSIZE;
 
                bscale = bsize >> DEV_BSHIFT;
+
+               nra = uimax(16 * MAXPHYS / bsize - 1, 511);
+               rablks = kmem_alloc(nra * sizeof(*rablks), KM_SLEEP);
+               rasizes = kmem_alloc(nra * sizeof(*rasizes), KM_SLEEP);
+               lastbn = ((uio->uio_offset + uio->uio_resid - 1) >> DEV_BSHIFT)
+                   &~ (bscale - 1);
+               nrablks = ratogo = 0;
                do {
                        bn = (uio->uio_offset >> DEV_BSHIFT) &~ (bscale - 1);
                        on = uio->uio_offset % bsize;
                        n = uimin((unsigned)(bsize - on), uio->uio_resid);
-                       error = bread(vp, bn, bsize, 0, &bp);
-                       if (error) {
-                               return (error);
+
+                       if (ratogo == 0) {
+                               nrablks = uimin((lastbn - bn) / bscale, nra);
+                               ratogo = nrablks;
+
+                               for (i = 0; i < nrablks; ++i) {
+                                       rablks[i] = bn + (i+1) * bscale;
+                                       rasizes[i] = bsize;
+                               }
+
+                               error = breadn(vp, bn, bsize,
+                                              rablks, rasizes, nrablks,
+                                              0, &bp);
+                       } else {
+                               if (ratogo > 0)
+                                       --ratogo;
+                               error = bread(vp, bn, bsize, 0, &bp);
                        }
+                       if (error)
+                               break;
                        n = uimin(n, bsize - bp->b_resid);
                        error = uiomove((char *)bp->b_data + on, n, uio);
                        brelse(bp, 0);
                } while (error == 0 && uio->uio_resid > 0 && n != 0);
+
+               kmem_free(rablks, nra * sizeof(*rablks));
+               kmem_free(rasizes, nra * sizeof(*rasizes));
+
                return (error);
 
        default: