On Fri, 24 Jul 2009 23:32:19 +0200Jörn Engel <joern@xxxxxxxxx> wrote:
> On Tue, 21 July 2009 01:46:41 +0200, Arnd Bergmann wrote:> > On Friday 17 July 2009, Greg Kroah-Hartman wrote:> > > @@ -43,7 +43,7 @@ typedef struct _RING_BUFFER {> > > // volatile u32 InterruptMask;> > > // Ring data starts here + RingDataStartOffset !!! DO NOT place any fields below this !!!> > > u8 Buffer[0];> > > -} STRUCT_PACKED RING_BUFFER;> > > +} __attribute__((packed)) RING_BUFFER;> > > > > > > The data structure is actually packed already, the attribute does not make it better> > and could be removed. We also have __packed as a shortcut for __attribute__((packed)).> > Honestly, I don't know how useful __packed really is. In a shared> kernel/userspace header, it is only defined for the kernel.>
As I remember, gcc generates worse code for packed structures on many architecturessince it may have to do byte fetchs/recombining to avoid unalignedaccesses.
-- _______________________________________________Virtualization mailing listVirtualization@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx://lists.linux-foundation.org/mailman/listinfo/virtualization
