Re: [Qemu-devel] [PATCH] migration: ram_handle_compressed

["Michael R. Hines" <mrhines@linux.vnet.ibm.com>]

On 09/18/2013 06:07 AM, Isaku Yamahata wrote:
> ram_handle_compressed() should be aware size > TARGET_PAGE_SIZE
> migration-rdma can call it with larger size.
>
> Signed-off-by: Isaku Yamahata <yamahata@private.email.ne.jp>
> ---
>   arch_init.c |   21 ++++++++++++++-------
>   1 file changed, 14 insertions(+), 7 deletions(-)
>
> diff --git a/arch_init.c b/arch_init.c
> index e47e139..64c81b0 100644
> --- a/arch_init.c
> +++ b/arch_init.c
> @@ -844,15 +844,22 @@ static inline void *host_from_stream_offset(QEMUFile *f,
>    */
>   void ram_handle_compressed(void *host, uint8_t ch, uint64_t size)
>   {
> -    if (ch != 0 || !is_zero_page(host)) {
> -        memset(host, ch, size);
> +    uint64_t pagesize = getpagesize();
> +    while (size > 0) {
> +        uint64_t length = MIN(pagesize, size);
> +
> +        if (ch !=0 || buffer_find_nonzero_offset(host, length) != length) {
> +            memset(host, ch, length);
>   #ifndef _WIN32
> -        if (ch == 0 &&
> -            (!kvm_enabled() || kvm_has_sync_mmu()) &&
> -            getpagesize() <= TARGET_PAGE_SIZE) {
> -            qemu_madvise(host, TARGET_PAGE_SIZE, QEMU_MADV_DONTNEED);
> -        }
> +            if (ch == 0 &&
> +                (!kvm_enabled() || kvm_has_sync_mmu()) && pagesize <= length) {
> +                qemu_madvise(host, size, QEMU_MADV_DONTNEED);
> +            }
>   #endif
> +        }
> +
> +        size -= length;
> +        host += length;
>       }
>   }
>

What is the reason for breaking the madvise() into smaller pieces?

- Michael