migration: do not overwrite zero pages
on incoming migration do not memset pages to zero if they already read as zero. this will allocate a new zero page and consume memory unnecessarily. even if we madvise a MADV_DONTNEED later this will only deallocate the memory asynchronously. Signed-off-by: Peter Lieven <pl@kamp.de> Signed-off-by: Juan Quintela <quintela@redhat.com>
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@ -835,6 +835,7 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
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}
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ch = qemu_get_byte(f);
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if (ch != 0 || !is_zero_page(host)) {
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memset(host, ch, TARGET_PAGE_SIZE);
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#ifndef _WIN32
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if (ch == 0 &&
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@ -843,6 +844,7 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
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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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} else if (flags & RAM_SAVE_FLAG_PAGE) {
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void *host;
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