[Xen-changelog] [xen-unstable] minios: Optimize mmap(open("/dev/mem"))

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1256288385 -3600
# Node ID 4a65bd76e09b152053202b2e58b536264935e6ef
# Parent  37829fd7c1e3faf19f77058ab604fd79dee194d0
minios: Optimize mmap(open("/dev/mem"))

Set map_frames_ex's stride parameter to 0 and increment to 1 to avoid
building an explicit list of mfns.

Signed-Off-By: Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>
---
 extras/mini-os/lib/sys.c |    7 ++-----
 1 files changed, 2 insertions(+), 5 deletions(-)

diff -r 37829fd7c1e3 -r 4a65bd76e09b extras/mini-os/lib/sys.c
--- a/extras/mini-os/lib/sys.c  Wed Oct 21 16:08:28 2009 +0100
+++ b/extras/mini-os/lib/sys.c  Fri Oct 23 09:59:45 2009 +0100
@@ -1256,11 +1256,8 @@ void *mmap(void *start, size_t length, i
         unsigned long zero = 0;
         return map_frames_ex(&zero, n, 0, 0, 1, DOMID_SELF, 0, 0);
     } else if (files[fd].type == FTYPE_MEM) {
-        int i;
-        unsigned long mfns[n];
-        for (i = 0; i < n; i++)
-            mfns[i] = ((unsigned long) offset + (i * PAGE_SIZE)) >> PAGE_SHIFT;
-        return map_frames_ex(mfns, n, 1, 0, 1, DOMID_IO, 0, 
_PAGE_PRESENT|_PAGE_RW);
+        unsigned long first_mfn = offset >> PAGE_SHIFT;
+        return map_frames_ex(&first_mfn, n, 0, 1, 1, DOMID_IO, 0, 
_PAGE_PRESENT|_PAGE_RW);
     } else ASSERT(0);
 }
 

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