Am 08.04.2013 um 10:33 schrieb Peter Lieven <p...@kamp.de>:
>
> 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.
>>
>
actually this might be better?!:
diff --git a/exec.c b/exec.c
index 786987a..334a46e 100644
--- a/exec.c
+++ b/exec.c
@@ -1071,6 +1071,11 @@ ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size, void
*host,
memory_try_enable_merging(new_block->host, size);
}
}
+ if (mem_prealloc) {
+ memset(new_block->host, size, 0x00);
+ } else {
+ qemu_madvise(new_block->host, size, QEMU_MADV_DONTNEED);
+ }
new_block->length = size;
/* Keep the list sorted from biggest to smallest block. */
