[src/trunk]: src/sys/uvm switch swap space allocation code to use blist inste...

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

details:   https://anonhg.NetBSD.org/src/rev/be4fbb365894
branches:  trunk
changeset: 580049:be4fbb365894
user:      yamt <yamt%NetBSD.org@localhost>
date:      Wed Apr 06 13:51:33 2005 +0000

description:
switch swap space allocation code to use blist instead of extent(9).
fix "warning: resource shortage: %d pages of swap lost".

extent(9) has some undesirable characteristics for swap allocation:
        - it involves alloc-to-free.
        - its operational cost is O(n*n) where n is number of entries.

diffstat:

 sys/uvm/uvm_swap.c |  50 ++++++++++++++++++++------------------------------
 1 files changed, 20 insertions(+), 30 deletions(-)

diffs (150 lines):

diff -r 31f9dc5b1761 -r be4fbb365894 sys/uvm/uvm_swap.c
--- a/sys/uvm/uvm_swap.c        Wed Apr 06 13:49:31 2005 +0000
+++ b/sys/uvm/uvm_swap.c        Wed Apr 06 13:51:33 2005 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: uvm_swap.c,v 1.89 2004/10/28 07:07:47 yamt Exp $       */
+/*     $NetBSD: uvm_swap.c,v 1.90 2005/04/06 13:51:33 yamt Exp $       */
 
 /*
  * Copyright (c) 1995, 1996, 1997 Matthew R. Green
@@ -32,7 +32,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uvm_swap.c,v 1.89 2004/10/28 07:07:47 yamt Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uvm_swap.c,v 1.90 2005/04/06 13:51:33 yamt Exp $");
 
 #include "fs_nfs.h"
 #include "opt_uvmhist.h"
@@ -53,6 +53,7 @@
 #include <sys/vnode.h>
 #include <sys/file.h>
 #include <sys/extent.h>
+#include <sys/blist.h>
 #include <sys/mount.h>
 #include <sys/pool.h>
 #include <sys/sa.h>
@@ -135,8 +136,7 @@
        int                     swd_npgbad;     /* #pages bad */
        int                     swd_drumoffset; /* page0 offset in drum */
        int                     swd_drumsize;   /* #pages in drum */
-       struct extent           *swd_ex;        /* extent for this swapdev */
-       char                    swd_exname[12]; /* name of extent above */
+       blist_t                 swd_blist;      /* blist for this swapdev */
        struct vnode            *swd_vp;        /* backing vnode */
        CIRCLEQ_ENTRY(swapdev)  swd_next;       /* priority circleq */
 
@@ -767,7 +767,6 @@
        struct proc *p;
        struct swapdev *sdp;
 {
-       static int count = 0;   /* static */
        struct vnode *vp;
        int error, npages, nblocks, size;
        long addr;
@@ -889,17 +888,10 @@
        /*
         * now we need to allocate an extent to manage this swap device
         */
-       snprintf(sdp->swd_exname, sizeof(sdp->swd_exname), "swap0x%04x",
-           count++);
 
-       /* note that extent_create's 3rd arg is inclusive, thus "- 1" */
-       sdp->swd_ex = extent_create(sdp->swd_exname, 0, npages - 1, M_VMSWAP,
-                                   0, 0, EX_WAITOK);
-       /* allocate the `saved' region from the extent so it won't be used */
-       if (addr) {
-               if (extent_alloc_region(sdp->swd_ex, 0, addr, EX_WAITOK))
-                       panic("disklabel region");
-       }
+       sdp->swd_blist = blist_create(npages);
+       /* mark all expect the `saved' region free. */
+       blist_free(sdp->swd_blist, addr, size);
 
        /*
         * if the vnode we are swapping to is the root vnode
@@ -933,9 +925,9 @@
                if (rootpages > size)
                        panic("swap_on: miniroot larger than swap?");
 
-               if (extent_alloc_region(sdp->swd_ex, addr,
-                                       rootpages, EX_WAITOK))
+               if (rootpages != blist_fill(sdp->swd_blist, addr, rootpages)) {
                        panic("swap_on: unable to preserve miniroot");
+               }
 
                size -= rootpages;
                printf("Preserved %d pages of miniroot ", rootpages);
@@ -979,8 +971,8 @@
         */
 
 bad:
-       if (sdp->swd_ex) {
-               extent_destroy(sdp->swd_ex);
+       if (sdp->swd_blist) {
+               blist_destroy(sdp->swd_blist);
        }
        if (vp != rootvp) {
                (void)VOP_CLOSE(vp, FREAD|FWRITE, p->p_ucred, p);
@@ -1055,7 +1047,7 @@
         */
        extent_free(swapmap, sdp->swd_drumoffset, sdp->swd_drumsize,
                    EX_WAITOK);
-       extent_destroy(sdp->swd_ex);
+       blist_destroy(sdp->swd_blist);
        bufq_free(&sdp->swd_tab);
        free(sdp, M_VMSWAP);
        return (0);
@@ -1463,7 +1455,6 @@
 {
        struct swapdev *sdp;
        struct swappri *spp;
-       u_long  result;
        UVMHIST_FUNC("uvm_swap_alloc"); UVMHIST_CALLED(pdhist);
 
        /*
@@ -1480,16 +1471,18 @@
 ReTry: /* XXXMRG */
        LIST_FOREACH(spp, &swap_priority, spi_swappri) {
                CIRCLEQ_FOREACH(sdp, &spp->spi_swapdev, swd_next) {
+                       uint64_t result;
+
                        /* if it's not enabled, then we can't swap from it */
                        if ((sdp->swd_flags & SWF_ENABLE) == 0)
                                continue;
                        if (sdp->swd_npginuse + *nslots > sdp->swd_npages)
                                continue;
-                       if (extent_alloc(sdp->swd_ex, *nslots, EX_NOALIGN,
-                                        EX_NOBOUNDARY, EX_MALLOCOK|EX_NOWAIT,
-                                        &result) != 0) {
+                       result = blist_alloc(sdp->swd_blist, *nslots);
+                       if (result == BLIST_NONE) {
                                continue;
                        }
+                       KASSERT(result < sdp->swd_drumsize);
 
                        /*
                         * successful allocation!  now rotate the circleq.
@@ -1510,7 +1503,8 @@
        /* XXXMRG: BEGIN HACK */
        if (*nslots > 1 && lessok) {
                *nslots = 1;
-               goto ReTry;     /* XXXMRG: ugh!  extent should support this for us */
+               /* XXXMRG: ugh!  blist should support this for us */
+               goto ReTry;
        }
        /* XXXMRG: END HACK */
 
@@ -1598,11 +1592,7 @@
        KASSERT(uvmexp.nswapdev >= 1);
        KASSERT(sdp != NULL);
        KASSERT(sdp->swd_npginuse >= nslots);
-       if (extent_free(sdp->swd_ex, startslot - sdp->swd_drumoffset, nslots,
-                       EX_MALLOCOK|EX_NOWAIT) != 0) {
-               printf("warning: resource shortage: %d pages of swap lost\n",
-                       nslots);
-       }
+       blist_free(sdp->swd_blist, startslot - sdp->swd_drumoffset, nslots);
        sdp->swd_npginuse -= nslots;
        uvmexp.swpginuse -= nslots;
        simple_unlock(&uvm.swap_data_lock);