commit 25f9e82e4ac93e71c6cf06fe2faa1899967db725
Author: Bryan Venteicher <bryanventeicher@gmail.com>
Date:   Sun Sep 29 13:56:42 2013 -0500

    Call blk_write() with a run of physically contiguous pages
    
    Previously, blk_write() was being called one page at a time, which
    would cause it to poll the console for every page. This change makes
    dumping a magnitude faster, and is especially useful on large memory
    machines.

diff --git a/sys/amd64/amd64/minidump_machdep.c b/sys/amd64/amd64/minidump_machdep.c
index f14c539..26b2b31 100644
--- a/sys/amd64/amd64/minidump_machdep.c
+++ b/sys/amd64/amd64/minidump_machdep.c
@@ -221,7 +221,8 @@ minidumpsys(struct dumperinfo *di)
 	vm_offset_t va;
 	int error;
 	uint64_t bits;
-	uint64_t *pml4, *pdp, *pd, *pt, pa;
+	uint64_t *pml4, *pdp, *pd, *pt, start_pa, pa;
+	size_t sz;
 	int i, ii, j, k, n, bit;
 	int retry_count;
 	struct minidumphdr mdhdr;
@@ -412,18 +413,29 @@ minidumpsys(struct dumperinfo *di)
 	}
 
 	/* Dump memory chunks */
-	/* XXX cluster it up and use blk_dump() */
-	for (i = 0; i < vm_page_dump_size / sizeof(*vm_page_dump); i++) {
+	for (i = 0, start_pa = 0, sz = 0;
+	     i < vm_page_dump_size / sizeof(*vm_page_dump); i++) {
 		bits = vm_page_dump[i];
 		while (bits) {
 			bit = bsfq(bits);
 			pa = (((uint64_t)i * sizeof(*vm_page_dump) * NBBY) + bit) * PAGE_SIZE;
-			error = blk_write(di, 0, pa, PAGE_SIZE);
-			if (error)
-				goto fail;
+			if (sz == 0 || start_pa + sz == pa) {
+				if (sz == 0)
+					start_pa = pa;
+				sz += PAGE_SIZE;
+			} else {
+				error = blk_write(di, 0, start_pa, sz);
+				if (error)
+					goto fail;
+				start_pa = pa;
+				sz = PAGE_SIZE;
+			}
 			bits &= ~(1ul << bit);
 		}
 	}
+	error = blk_write(di, 0, start_pa, sz);
+	if (error)
+		goto fail;
 
 	error = blk_flush(di);
 	if (error)