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From: Peter Wemm <peter@FreeBSD.org>
To: Perforce Change Reviews <perforce@freebsd.org>
Cc: 
Subject: PERFORCE change 80051 for review
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http://perforce.freebsd.org/chv.cgi?CH=80051

Change 80051 by peter@peter_overcee on 2005/07/12 20:30:33

	Check in some WIP code that we're experimenting with (default off) at
	work to see if we're seeing a 4K/2M page alias problem when atomic
	ops are mixed in.  This allows an expensive 4.x style temporary
	ephemeral mapping for each operation.

Affected files ...

.. //depot/projects/hammer/sys/amd64/amd64/uio_machdep.c#5 edit

Differences ...

==== //depot/projects/hammer/sys/amd64/amd64/uio_machdep.c#5 (text+ko) ====

@@ -48,6 +48,10 @@
 
 #include <vm/vm.h>
 #include <vm/vm_page.h>
+#ifdef NODMAP
+#include <vm/vm_extern.h>
+#include <vm/vm_kern.h>
+#endif
 
 #include <machine/vmparam.h>
 
@@ -65,11 +69,17 @@
 	size_t cnt;
 	int error = 0;
 	int save = 0;
+#ifdef NODMAP
+	vm_offset_t kva;
+#endif
 
 	KASSERT(uio->uio_rw == UIO_READ || uio->uio_rw == UIO_WRITE,
 	    ("uiomove_fromphys: mode"));
 	KASSERT(uio->uio_segflg != UIO_USERSPACE || uio->uio_td == curthread,
 	    ("uiomove_fromphys proc"));
+#ifdef NODMAP
+	kva = kmem_alloc_nofault(kernel_map, PAGE_SIZE);
+#endif
 	save = td->td_pflags & TDP_DEADLKTREAT;
 	td->td_pflags |= TDP_DEADLKTREAT;
 	while (n > 0 && uio->uio_resid) {
@@ -84,8 +94,13 @@
 			cnt = n;
 		page_offset = offset & PAGE_MASK;
 		cnt = min(cnt, PAGE_SIZE - page_offset);
+#ifdef NODMAP
+		pmap_kenter(kva, VM_PAGE_TO_PHYS(ma[offset >> PAGE_SHIFT]));
+		cp = (char *)kva + page_offset;
+#else
 		cp = (char *)PHYS_TO_DMAP(ma[offset >> PAGE_SHIFT]->phys_addr) +
 		    page_offset;
+#endif
 		switch (uio->uio_segflg) {
 		case UIO_USERSPACE:
 			if (ticks - PCPU_GET(switchticks) >= hogticks)
@@ -106,6 +121,9 @@
 		case UIO_NOCOPY:
 			break;
 		}
+#ifdef NODMAP
+		pmap_kremove(kva);
+#endif
 		iov->iov_base = (char *)iov->iov_base + cnt;
 		iov->iov_len -= cnt;
 		uio->uio_resid -= cnt;
@@ -116,5 +134,8 @@
 out:
 	if (save == 0)
 		td->td_pflags &= ~TDP_DEADLKTREAT;
+#ifdef NODMAP
+	kmem_free(kernel_map, kva, PAGE_SIZE);
+#endif
 	return (error);
 }