Am 08.04.2013 um 10:49 schrieb Kevin Wolf <kw...@redhat.com>: > Am 08.04.2013 um 10:33 hat Peter Lieven geschrieben: >> >> 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. */ > > It does. But perhaps Paolo's suggestion of using mmap() to allocate the > memory would be better. I'm not sure how MADV_DONTNEED behaves on > non-Linux.
its not guaranteed to zero memory. Peter > > Kevin
