RE: [Xen-ia64-devel] [PATCH] xentrace buffer alignment

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

>-----Original Message-----
>From: Masaki Kanno
>Sent: 2005年11月24日 17:21
>Hi, Rob, Kevin,
>
>> The alignment directive is necessary there since they're dynamically marked
>> on an allocated buf. Or how about adding padding bytes to avoid using 
>> compiler
>> directive and ifdef? Then, still no need for "t_rec".
>
>Sorry, "t_rec" alignment is mistake. I thought "sizeof(t_rec) = 52 bytes".
>
>The patch was made on Kevin's idea.
>However, I'm worried. When someone adds other members to "t_buf", isn't 
>alignment
>for ia64 forgotten?

I meant to add padding bytes like "char padding[4]" with warning to developer 
that 8 bytes alignment should be promised. But now I think your original 
".align" approach may be easier without concern how many padding bytes need to 
be there on different architecture. So you can send out a patch with your 
original ".align" approach (but remove "ifdef __ia64__" to xen mailing list 
since it's a common code modification. Also please keep a comment to warn 
alignment requirement here. ;-)

Thanks,
Kevin
>
>Signed-off-by: Masaki Kanno <kanno.masaki@xxxxxxxxxxxxxx>
>
>Thanks,
> kan
>
>diff -r 51f32d60536b xen/include/public/trace.h
>--- a/xen/include/public/trace.h        Fri Nov 18 00:35:14 2005
>+++ b/xen/include/public/trace.h        Thu Nov 24 18:04:31 2005
>@@ -69,6 +69,7 @@
>     unsigned int  prod;      /* Next item to be produced by Xen.           */
>     unsigned int  nr_recs;   /* Number of records in this trace buffer.    */
>     /* 'nr_recs' records follow immediately after the meta-data header.    */
>+    unsigned int  align_buf; /* 8 bytes alignment for ia64                 */
> };
>
> #endif /* __XEN_PUBLIC_TRACE_H__ */
>
>
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