48 lines
1.7 KiB
Diff
48 lines
1.7 KiB
Diff
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From b96534d01807de76afa262568e156156c0a6fdd6 Mon Sep 17 00:00:00 2001
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From: Peter Lieven <pl@kamp.de>
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Date: Thu, 24 Oct 2013 09:21:29 +0200
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Subject: [PATCH] migration: drop MADVISE_DONT_NEED for incoming zero pages
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The madvise for zeroed out pages was introduced when every transferred
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zero page was memset to zero and thus allocated. Since commit
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211ea740 we check for zeroness of a target page before we memset
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it to zero. Additionally we memmap target memory so it is essentially
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zero initialized (except for e.g. option roms and bios which are loaded
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into target memory although they shouldn't).
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It was reported recently that this madvise causes a performance degradation
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in some situations. As the madvise should only be called rarely and if it's called
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it is likely on a busy page (it was non-zero and changed to zero during migration)
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drop it completely.
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Reported-By: Zhang Haoyu <haoyu.zhang@huawei.com>
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Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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Signed-off-by: Peter Lieven <pl@kamp.de>
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Signed-off-by: Juan Quintela <quintela@redhat.com>
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(cherry picked from commit fc1c4a5d32e15a4c40c47945da85ef9c1e0c1b54)
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Conflicts:
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arch_init.c
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---
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arch_init.c | 7 -------
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1 file changed, 7 deletions(-)
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diff --git a/arch_init.c b/arch_init.c
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index 68a7ab7..23151b3 100644
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--- a/arch_init.c
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+++ b/arch_init.c
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@@ -845,13 +845,6 @@ void ram_handle_compressed(void *host, uint8_t ch, uint64_t size)
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{
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if (ch != 0 || !is_zero_page(host)) {
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memset(host, ch, size);
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-#ifndef _WIN32
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- if (ch == 0 &&
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- (!kvm_enabled() || kvm_has_sync_mmu()) &&
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- getpagesize() <= TARGET_PAGE_SIZE) {
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- qemu_madvise(host, TARGET_PAGE_SIZE, QEMU_MADV_DONTNEED);
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- }
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-#endif
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}
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}
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