| Message ID | 1309180927-19003-4-git-send-email-avi@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 2011-06-27 15:21, Avi Kivity wrote: > Simple implementations of memory routers, for example the Cirrus VGA memory banks > or the 440FX PAM registers can generate adjacent memory regions which are contiguous. > Detect these and merge them; this saves kvm memory slots and shortens lookup times. That reminds me of KVM_CAP_JOIN_MEMORY_REGIONS_WORKS. Have you checked if things still work in the absence of the feature or if we need to lift our requirements on the host kernel (would be 2.6.30, not that problematic)? Jan
On 06/27/2011 04:56 PM, Jan Kiszka wrote: > On 2011-06-27 15:21, Avi Kivity wrote: > > Simple implementations of memory routers, for example the Cirrus VGA memory banks > > or the 440FX PAM registers can generate adjacent memory regions which are contiguous. > > Detect these and merge them; this saves kvm memory slots and shortens lookup times. > > That reminds me of KVM_CAP_JOIN_MEMORY_REGIONS_WORKS. Have you checked > if things still work in the absence of the feature or if we need to lift > our requirements on the host kernel (would be 2.6.30, not that problematic)? Good catch. We should probably disable merging if it doesn't work. Or we should declare that a kernel bug should be fixed in the kernel, not userspace, and backport the fix to 2.6.27.whatever.
diff --git a/memory.c b/memory.c index d962fff..f136714 100644 --- a/memory.c +++ b/memory.c @@ -122,6 +122,27 @@ static void flatview_destroy(FlatView *view) qemu_free(view->ranges); } +/* Attempt to simplify a view by merging ajacent ranges */ +static void flatview_simplify(FlatView *view) +{ + unsigned i; + FlatRange *r1, *r2; + + for (i = 0; i + 1 < view->nr; ++i) { + r1 = &view->ranges[i]; + r2 = &view->ranges[i+1]; + if (addrrange_end(r1->addr) == r2->addr.start + && r1->mr == r2->mr + && r1->offset_in_region + r1->addr.size == r2->offset_in_region + && r1->dirty_log_mask == r2->dirty_log_mask) { + r1->addr.size += r2->addr.size; + memmove(r2, r2 + 1, (view->nr - (i + 2)) * sizeof(*r2)); + --view->nr; + --i; + } + } +} + /* Render a memory region into the global view. Ranges in @view obscure * ranges in @mr. */ @@ -209,6 +230,7 @@ static FlatView generate_memory_topology(MemoryRegion *mr) flatview_init(&view); render_memory_region(&view, mr, 0, addrrange_make(0, UINT64_MAX)); + flatview_simplify(&view); return view; }
Simple implementations of memory routers, for example the Cirrus VGA memory banks or the 440FX PAM registers can generate adjacent memory regions which are contiguous. Detect these and merge them; this saves kvm memory slots and shortens lookup times. Signed-off-by: Avi Kivity <avi@redhat.com> --- memory.c | 22 ++++++++++++++++++++++ 1 files changed, 22 insertions(+), 0 deletions(-)