Implement write combining for crashdumps. This is useful when

write caching is disabled on both SCSI and IDE disks where large
memory dumps could take up to an hour to complete.

Taking an i386 scsi based system with 512MB of ram and timing (in
seconds) how long it took to complete a dump, the following results
were obtained:

Before:				After:
	WCE           TIME		WCE           TIME
	------------------		------------------
	1	141.820972		1	 15.600111
	0	797.265072		0	 65.480465

Obtained from:	Yahoo!
Reviewed by:	peter

sys/alpha/alpha/pmap.c

@@ -2223,9 +2223,9 @@ retry:
  * during dump.
  */
 void *
-pmap_kenter_temporary(vm_offset_t pa)
+pmap_kenter_temporary(vm_offset_t pa, int i)
 {
-	return (void *) ALPHA_PHYS_TO_K0SEG(pa);
+	return (void *) ALPHA_PHYS_TO_K0SEG(pa - (i * PAGE_SIZE));
 }
 
 #define MAX_INIT_PT (96)

sys/alpha/include/param.h

@@ -107,6 +107,7 @@
 #endif
 #define DFLTPHYS	(64 * 1024)	/* default max raw I/O transfer size */
 #define MAXPHYS		(128 * 1024)	/* max raw I/O transfer size */
+#define MAXDUMPPGS	(DFLTPHYS/PAGE_SIZE)
 
 #define	CLSIZE		1
 #define	CLSIZELOG2	0

sys/amd64/amd64/pmap.c

@@ -182,6 +182,12 @@ static caddr_t CADDR2;
 static pt_entry_t *msgbufmap;
 struct msgbuf *msgbufp=0;
 
+/*
+ * Crashdump maps.
+ */
+static pt_entry_t *pt_crashdumpmap;
+static caddr_t crashdumpmap;
+
 #ifdef SMP
 extern pt_entry_t *SMPpt;
 #else
@@ -333,6 +339,11 @@ pmap_bootstrap(firstaddr, loadaddr)
 	SYSMAP(caddr_t, CMAP1, CADDR1, 1)
 	SYSMAP(caddr_t, CMAP2, CADDR2, 1)
 
+	/*
+	 * Crashdump maps.
+	 */
+	SYSMAP(caddr_t, pt_crashdumpmap, crashdumpmap, MAXDUMPPGS);
+
 	/*
 	 * ptvmmap is used for reading arbitrary physical pages via /dev/mem.
 	 * XXX ptmmap is not used.
@@ -2231,10 +2242,10 @@ retry:
  * to be used for panic dumps.
  */
 void *
-pmap_kenter_temporary(vm_offset_t pa)
+pmap_kenter_temporary(vm_offset_t pa, int i)
 {
-	pmap_kenter((vm_offset_t)CADDR1, pa);
+	pmap_kenter((vm_offset_t)crashdumpmap + (i * PAGE_SIZE), pa);
-	return ((void *)CADDR1);
+	return ((void *)crashdumpmap);
 }
 
 #define MAX_INIT_PT (96)

sys/cam/scsi/scsi_da.c

@@ -634,7 +634,9 @@ dadump(dev_t dev)
 	long	    blkcnt;
 	vm_offset_t addr;	
 	struct	    ccb_scsiio csio;
+	int         dumppages = MAXDUMPPGS;
 	int	    error;
+	int         i;
 
 	/* toss any characters present prior to dump */
 	while (cncheckc() != -1)
@@ -659,12 +661,17 @@ dadump(dev_t dev)
 	blkcnt = howmany(PAGE_SIZE, secsize);
 
 	while (num > 0) {
-		void *va;
+		caddr_t va;
 
-		if (is_physical_memory(addr)) {
+		if ((num / blkcnt) < dumppages)
-			va = pmap_kenter_temporary(trunc_page(addr));
+			dumppages = num / blkcnt;
-		} else {
+
-			va = pmap_kenter_temporary(trunc_page(0));
+		for (i = 0; i < dumppages; ++i) {
+			vm_offset_t a = addr + (i * PAGE_SIZE);
+			if (is_physical_memory(a))
+				va = pmap_kenter_temporary(trunc_page(a), i);
+			else
+				va = pmap_kenter_temporary(trunc_page(0), i);
 		}
 
 		xpt_setup_ccb(&csio.ccb_h, periph->path, /*priority*/1);
@@ -677,9 +684,9 @@ dadump(dev_t dev)
 				/*byte2*/0,
 				/*minimum_cmd_size*/ softc->minimum_cmd_size,
 				blknum,
-				blkcnt,
+				blkcnt * dumppages,
 				/*data_ptr*/(u_int8_t *) va,
-				/*dxfer_len*/blkcnt * secsize,
+				/*dxfer_len*/blkcnt * secsize * dumppages,
 				/*sense_len*/SSD_FULL_SIZE,
 				DA_DEFAULT_TIMEOUT * 1000);		
 		xpt_polled_action((union ccb *)&csio);
@@ -706,9 +713,9 @@ dadump(dev_t dev)
 		}
 		
 		/* update block count */
-		num -= blkcnt;
+		num -= blkcnt * dumppages;
-		blknum += blkcnt;
+		blknum += blkcnt * dumppages;
-		addr += PAGE_SIZE;
+		addr += PAGE_SIZE * dumppages;
 
 		/* operator aborting dump? */
 		if (cncheckc() != -1)

sys/dev/ata/ata-disk.c

@@ -257,7 +257,10 @@ addump(dev_t dev)
     struct ad_request request;
     u_int count, blkno, secsize;
     vm_offset_t addr = 0;
+    long blkcnt;
+    int dumppages = MAXDUMPPGS;
     int error;
+    int i;
 
     if ((error = disk_dumpcheck(dev, &count, &blkno, &secsize)))
 	return error;
@@ -269,18 +272,27 @@ addump(dev_t dev)
     adp->controller->mode[ATA_DEV(adp->unit)] = ATA_PIO;
     ata_reinit(adp->controller);
 
+    blkcnt = howmany(PAGE_SIZE, secsize);
+
     while (count > 0) {
 	caddr_t va;
 	DELAY(1000);
-	if (is_physical_memory(addr))
+
-	    va = pmap_kenter_temporary(trunc_page(addr));
+	if ((count / blkcnt) < dumppages)
+	    dumppages = count / blkcnt;
+
+	for (i = 0; i < dumppages; ++i) {
+	    vm_offset_t a = addr + (i * PAGE_SIZE);
+	    if (is_physical_memory(a))
+		va = pmap_kenter_temporary(trunc_page(a), i);
 	    else
-	    va = pmap_kenter_temporary(trunc_page(0));
+		va = pmap_kenter_temporary(trunc_page(0), i);
+	}
 
 	bzero(&request, sizeof(struct ad_request));
 	request.device = adp;
 	request.blockaddr = blkno;
-	request.bytecount = PAGE_SIZE;
+	request.bytecount = PAGE_SIZE * dumppages;
 	request.data = va;
 
 	while (request.bytecount > 0) {
@@ -300,9 +312,9 @@ addump(dev_t dev)
 	    printf("%ld ", (long)(count * DEV_BSIZE) / (1024 * 1024));
 	}
 
-	blkno += howmany(PAGE_SIZE, secsize);
+	blkno += blkcnt * dumppages;
-	count -= howmany(PAGE_SIZE, secsize);
+	count -= blkcnt * dumppages;
-	addr += PAGE_SIZE;
+	addr += PAGE_SIZE * dumppages;
 	if (cncheckc() != -1)
 	    return EINTR;
     }

sys/i386/i386/pmap.c

@@ -182,6 +182,12 @@ static caddr_t CADDR2;
 static pt_entry_t *msgbufmap;
 struct msgbuf *msgbufp=0;
 
+/*
+ * Crashdump maps.
+ */
+static pt_entry_t *pt_crashdumpmap;
+static caddr_t crashdumpmap;
+
 #ifdef SMP
 extern pt_entry_t *SMPpt;
 #else
@@ -333,6 +339,11 @@ pmap_bootstrap(firstaddr, loadaddr)
 	SYSMAP(caddr_t, CMAP1, CADDR1, 1)
 	SYSMAP(caddr_t, CMAP2, CADDR2, 1)
 
+	/*
+	 * Crashdump maps.
+	 */
+	SYSMAP(caddr_t, pt_crashdumpmap, crashdumpmap, MAXDUMPPGS);
+
 	/*
 	 * ptvmmap is used for reading arbitrary physical pages via /dev/mem.
 	 * XXX ptmmap is not used.
@@ -2231,10 +2242,10 @@ retry:
  * to be used for panic dumps.
  */
 void *
-pmap_kenter_temporary(vm_offset_t pa)
+pmap_kenter_temporary(vm_offset_t pa, int i)
 {
-	pmap_kenter((vm_offset_t)CADDR1, pa);
+	pmap_kenter((vm_offset_t)crashdumpmap + (i * PAGE_SIZE), pa);
-	return ((void *)CADDR1);
+	return ((void *)crashdumpmap);
 }
 
 #define MAX_INIT_PT (96)

sys/i386/include/param.h

@@ -96,6 +96,7 @@
 #endif
 #define DFLTPHYS	(64 * 1024)	/* default max raw I/O transfer size */
 #define MAXPHYS		(128 * 1024)	/* max raw I/O transfer size */
+#define MAXDUMPPGS	(DFLTPHYS/PAGE_SIZE)
 
 #define IOPAGES	2		/* pages of i/o permission bitmap */
 #define UPAGES	2		/* pages of u-area */

sys/ia64/ia64/pmap.c

@@ -1478,9 +1478,9 @@ pmap_enter_quick(pmap_t pmap, vm_offset_t va, vm_page_t m)
  * during dump.
  */
 void *
-pmap_kenter_temporary(vm_offset_t pa)
+pmap_kenter_temporary(vm_offset_t pa, int i)
 {
-	return (void *) IA64_PHYS_TO_RR7(pa);
+	return (void *) IA64_PHYS_TO_RR7(pa - (i * PAGE_SIZE));
 }
 
 #define MAX_INIT_PT (96)

sys/ia64/include/param.h

@@ -103,6 +103,7 @@
 #endif
 #define DFLTPHYS	(64 * 1024)	/* default max raw I/O transfer size */
 #define MAXPHYS		(128 * 1024)	/* max raw I/O transfer size */
+#define MAXDUMPPGS	(DFLTPHYS/PAGE_SIZE)
 
 #define	CLSIZE		1
 #define	CLSIZELOG2	0

sys/vm/pmap.h

@@ -140,7 +140,7 @@ void		 pmap_swapout_proc __P((struct proc *p));
 void		 pmap_swapin_proc __P((struct proc *p));
 void		 pmap_activate __P((struct proc *p));
 vm_offset_t	 pmap_addr_hint __P((vm_object_t obj, vm_offset_t addr, vm_size_t size));
-void		*pmap_kenter_temporary __P((vm_offset_t pa));
+void		*pmap_kenter_temporary __P((vm_offset_t pa, int i));
 void		 pmap_init2 __P((void));
 
 #endif /* _KERNEL */