Peter Lieven <p...@kamp.de> wrote:
> The madvise for zeroed out pages was introduced when every transferred
> zero page was memset to zero and thus allocated. Since commit
> 211ea740 we check for zeroness of a target page before we memset
> it to zero. Additionally we memmap target memory so it is essentially
> zero initialized (except for e.g. option roms and bios which are loaded
> into target memory although they shouldn't).
>
> It was reported recently that this madvise causes a performance degradation
> in some situations. As the madvise should only be called rarely and if it's
> called
> it is likely on a busy page (it was non-zero and changed to zero during
> migration)
> drop it completely.
Reviewed-by: Juan Quintela <quint...@redhat.com>
I take it. I am on KVM Forum/LinuxCon this week. Will send when back
at home.
Thanks.
>
> Reported-By: Zhang Haoyu <haoyu.zh...@huawei.com>
> Acked-by: Paolo Bonzini <pbonz...@redhat.com>
> Signed-off-by: Peter Lieven <p...@kamp.de>
> ---
> arch_init.c | 8 --------
> 1 file changed, 8 deletions(-)
>
> diff --git a/arch_init.c b/arch_init.c
> index 7545d96..e0acbc5 100644
> --- a/arch_init.c
> +++ b/arch_init.c
> @@ -850,14 +850,6 @@ void ram_handle_compressed(void *host, uint8_t ch,
> uint64_t size)
> {
> if (ch != 0 || !is_zero_range(host, size)) {
> memset(host, ch, size);
> -#ifndef _WIN32
> - if (ch == 0 && (!kvm_enabled() || kvm_has_sync_mmu())) {
> - size = size & ~(getpagesize() - 1);
> - if (size > 0) {
> - qemu_madvise(host, size, QEMU_MADV_DONTNEED);
> - }
> - }
> -#endif
> }
> }
