From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:44515) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VZFFV-0007xP-5j for qemu-devel@nongnu.org; Thu, 24 Oct 2013 03:22:33 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VZFFQ-0005Za-DV for qemu-devel@nongnu.org; Thu, 24 Oct 2013 03:22:29 -0400 Received: from mx.ipv6.kamp.de ([2a02:248:0:51::16]:47214 helo=mx01.kamp.de) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VZFFQ-0005ZW-1g for qemu-devel@nongnu.org; Thu, 24 Oct 2013 03:22:24 -0400 From: Peter Lieven Date: Thu, 24 Oct 2013 09:21:29 +0200 Message-Id: <1382599289-9503-1-git-send-email-pl@kamp.de> Subject: [Qemu-devel] [RESEND][PATCH] migration: drop MADVISE_DONT_NEED for incoming zero pages List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: quintela@redhat.com, haoyu.zhang@huawei.com, Peter Lieven , xiaoguangrong@linux.vnet.ibm.com, pbonzini@redhat.com, afaerber@suse.de 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 Acked-by: Paolo Bonzini Signed-off-by: Peter Lieven --- 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