Re: [Qemu-devel] [PATCH] snapshot: use local variable to bdrv_pwrite_sync L1 table

[Kevin Wolf <kwolf@redhat.com>]

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Am 23.10.2014 um 00:18 hat Eric Blake geschrieben:
> On 10/21/2014 03:24 AM, Max Reitz wrote:
> > On 2014-10-21 at 10:04, Zhang Haoyu wrote:
> >> Use local variable to bdrv_pwrite_sync L1 table,
> >> needless to make conversion of cached L1 table between
> >> big-endian and host style.
> >>
> >> Signed-off-by: Zhang Haoyu <zhanghy@sangfor.com>
> >> ---
> >>   block/qcow2-refcount.c | 22 +++++++---------------
> >>   1 file changed, 7 insertions(+), 15 deletions(-)
> >>
> 
> I know we're up to v5 and that Max already took it into his branch, but...
> 
> 
> >>       l1_size2 = l1_size * sizeof(uint64_t);
> >> +    l1_table = g_try_malloc0(align_offset(l1_size2, 512));
> > 
> > I wanted to propose using qemu_try_blockalign(), but since it'd require
> > a memset() afterwards, it gets rather ugly.
> 
> Not after this recent patch:
> 
> https://lists.gnu.org/archive/html/qemu-devel/2014-10/msg02499.html

We can switch to qemu_try_blockalign0() in a follow-up patch.

But this is far from being a fast path, so there is very little to gain
anyway.

Kevin

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