diff options
| author | aliguori <aliguori@c046a42c-6fe2-441c-8c8c-71466251a162> | 2008-12-09 20:09:57 +0000 |
|---|---|---|
| committer | aliguori <aliguori@c046a42c-6fe2-441c-8c8c-71466251a162> | 2008-12-09 20:09:57 +0000 |
| commit | f65ed4c1529f29a7d62d6733eaa50bed24a4b2ed (patch) | |
| tree | 1d0351afc0542f8f709f9ed7f6a445474b137a9e /hw/vga.c | |
| parent | d85dc283fa87353be10b11b463196d10eb49ca41 (diff) | |
| download | qemu-f65ed4c1529f29a7d62d6733eaa50bed24a4b2ed.tar.gz | |
KVM: Coalesced MMIO support
MMIO exits are more expensive in KVM or Xen than in QEMU because they
involve, at least, privilege transitions. However, MMIO write
operations can be effectively batched if those writes do not have side
effects.
Good examples of this include VGA pixel operations when in a planar
mode. As it turns out, we can get a nice boost in other areas too.
Laurent mentioned a 9.7% performance boost in iperf with the coalesced
MMIO changes for the e1000 when he originally posted this work for KVM.
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5961 c046a42c-6fe2-441c-8c8c-71466251a162
Diffstat (limited to 'hw/vga.c')
| -rw-r--r-- | hw/vga.c | 2 |
1 files changed, 2 insertions, 0 deletions
@@ -2256,6 +2256,7 @@ void vga_init(VGAState *s) vga_io_memory = cpu_register_io_memory(0, vga_mem_read, vga_mem_write, s); cpu_register_physical_memory(isa_mem_base + 0x000a0000, 0x20000, vga_io_memory); + qemu_register_coalesced_mmio(isa_mem_base + 0x000a0000, 0x20000); } /* Memory mapped interface */ @@ -2330,6 +2331,7 @@ static void vga_mm_init(VGAState *s, target_phys_addr_t vram_base, cpu_register_physical_memory(ctrl_base, 0x100000, s_ioport_ctrl); s->bank_offset = 0; cpu_register_physical_memory(vram_base + 0x000a0000, 0x20000, vga_io_memory); + qemu_register_coalesced_mmio(vram_base + 0x000a0000, 0x20000); } int isa_vga_init(DisplayState *ds, uint8_t *vga_ram_base, |