Am 05.04.2013 um 21:23 schrieb Kevin Wolf <kw...@redhat.com>:
> Am 26.03.2013 um 10:58 hat Peter Lieven geschrieben:
>> virtually all dup pages are zero pages. remove
>> the special is_dup_page() function and use the
>> optimized buffer_find_nonzero_offset() function
>> instead.
>>
>> here buffer_find_nonzero_offset() is used directly
>> to avoid the unnecssary additional checks in
>> buffer_is_zero().
>>
>> raw performace gain checking 1 GByte zeroed memory
>> over is_dup_page() is approx. 10-12% with SSE2
>> and 8-10% with unsigned long arithmedtic.
>>
>> Signed-off-by: Peter Lieven <p...@kamp.de>
>> Reviewed-by: Orit Wasserman <owass...@redhat.com>
>> Reviewed-by: Eric Blake <ebl...@redhat.com>
>
> Okay, so I bisected again and this is the second patch that is involved
> in the slowness of qemu-iotests case 007.
>
Can you try if the following solves your issue:
diff --git a/exec.c b/exec.c
index 786987a..54baa4a 100644
--- a/exec.c
+++ b/exec.c
@@ -1071,6 +1071,7 @@ ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size, void
*host,
memory_try_enable_merging(new_block->host, size);
}
}
+ qemu_madvise(new_block->host, size, QEMU_MADV_DONTNEED);
new_block->length = size;
/* Keep the list sorted from biggest to smallest block. */
BR,
Peter
