The comments of ram_handle_compressed needs to be changed accordingly, "Do not memset pages to zero if they already read as zero to avoid allocating zero pages and consuming memory unnecessarily."
Thanks, Zhang Haoyu > 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. > > 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 > } > } > > -- > 1.7.9.5 >