[Qemu-devel] Re: [PATCH 09/10] kvm: port qemu-kvm's bitmap scanning

[Yoshiaki Tamura <tamura.yoshiaki@lab.ntt.co.jp>]

Hi,

This patch may conflict with the patch I posted on April 19.

http://www.mail-archive.com/qemu-devel@nongnu.org/msg29941.html

If Marcelo's is going to be merged, I need to rebase the above to it.
It would be helpful if you could tell me the plan.

Thanks,

Yoshi

2010/4/27 Marcelo Tosatti <mtosatti@redhat.com>:
> Which is significantly faster.
>
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> ---
>  kvm-all.c |   53 +++++++++++++++++++++++++++++++++++++----------------
>  1 files changed, 37 insertions(+), 16 deletions(-)
>
> diff --git a/kvm-all.c b/kvm-all.c
> index eabb097..ef45418 100644
> --- a/kvm-all.c
> +++ b/kvm-all.c
> @@ -26,6 +26,7 @@
>  #include "hw/hw.h"
>  #include "gdbstub.h"
>  #include "kvm.h"
> +#include "bswap.h"
>
>  /* KVM uses PAGE_SIZE in it's definition of COALESCED_MMIO_MAX */
>  #define PAGE_SIZE TARGET_PAGE_SIZE
> @@ -282,11 +283,41 @@ static int kvm_set_migration_log(int enable)
>     return 0;
>  }
>
> -static int test_le_bit(unsigned long nr, unsigned char *addr)
> +/* get kvm's dirty pages bitmap and update qemu's */
> +static int kvm_get_dirty_pages_log_range(unsigned long start_addr,
> +                                         unsigned long *bitmap,
> +                                         unsigned long offset,
> +                                         unsigned long mem_size)
>  {
> -    return (addr[nr >> 3] >> (nr & 7)) & 1;
> +    unsigned int i, j;
> +    unsigned long page_number, addr, addr1, c;
> +    ram_addr_t ram_addr;
> +    unsigned int len = ((mem_size / TARGET_PAGE_SIZE) + HOST_LONG_BITS - 1) /
> +        HOST_LONG_BITS;
> +
> +    /*
> +     * bitmap-traveling is faster than memory-traveling (for addr...)
> +     * especially when most of the memory is not dirty.
> +     */
> +    for (i = 0; i < len; i++) {
> +        if (bitmap[i] != 0) {
> +            c = leul_to_cpu(bitmap[i]);
> +            do {
> +                j = ffsl(c) - 1;
> +                c &= ~(1ul << j);
> +                page_number = i * HOST_LONG_BITS + j;
> +                addr1 = page_number * TARGET_PAGE_SIZE;
> +                addr = offset + addr1;
> +                ram_addr = cpu_get_physical_page_desc(addr);
> +                cpu_physical_memory_set_dirty(ram_addr);
> +            } while (c != 0);
> +        }
> +    }
> +    return 0;
>  }
>
> +#define ALIGN(x, y)  (((x)+(y)-1) & ~((y)-1))
> +
>  /**
>  * kvm_physical_sync_dirty_bitmap - Grab dirty bitmap from kernel space
>  * This function updates qemu's dirty bitmap using cpu_physical_memory_set_dirty().
> @@ -300,8 +331,6 @@ static int kvm_physical_sync_dirty_bitmap(target_phys_addr_t start_addr,
>  {
>     KVMState *s = kvm_state;
>     unsigned long size, allocated_size = 0;
> -    target_phys_addr_t phys_addr;
> -    ram_addr_t addr;
>     KVMDirtyLog d;
>     KVMSlot *mem;
>     int ret = 0;
> @@ -313,7 +342,7 @@ static int kvm_physical_sync_dirty_bitmap(target_phys_addr_t start_addr,
>             break;
>         }
>
> -        size = ((mem->memory_size >> TARGET_PAGE_BITS) + 7) / 8;
> +        size = ALIGN(((mem->memory_size) >> TARGET_PAGE_BITS), HOST_LONG_BITS) / 8;
>         if (!d.dirty_bitmap) {
>             d.dirty_bitmap = qemu_malloc(size);
>         } else if (size > allocated_size) {
> @@ -330,17 +359,9 @@ static int kvm_physical_sync_dirty_bitmap(target_phys_addr_t start_addr,
>             break;
>         }
>
> -        for (phys_addr = mem->start_addr, addr = mem->phys_offset;
> -             phys_addr < mem->start_addr + mem->memory_size;
> -             phys_addr += TARGET_PAGE_SIZE, addr += TARGET_PAGE_SIZE) {
> -            unsigned char *bitmap = (unsigned char *)d.dirty_bitmap;
> -            unsigned nr = (phys_addr - mem->start_addr) >> TARGET_PAGE_BITS;
> -
> -            if (test_le_bit(nr, bitmap)) {
> -                cpu_physical_memory_set_dirty(addr);
> -            }
> -        }
> -        start_addr = phys_addr;
> +        kvm_get_dirty_pages_log_range(mem->start_addr, d.dirty_bitmap,
> +                                      mem->start_addr, mem->memory_size);
> +        start_addr = mem->start_addr + mem->memory_size;
>     }
>     qemu_free(d.dirty_bitmap);
>
> --
> 1.6.6.1