On 12/06/2010 10:38 PM, David Sharp wrote:
On Sat, Dec 4, 2010 at 12:11 AM, Avi Kivity<avi@xxxxxxxxxx> wrote: > On 12/04/2010 02:13 AM, David Sharp wrote: >> >> Signed-off-by: David Sharp<dhsharp@xxxxxxxxxx> >> --- >> arch/x86/kvm/trace.h | 8 ++++---- >> 1 files changed, 4 insertions(+), 4 deletions(-) >> >> diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h >> index a6544b8..ab41fb0 100644 >> --- a/arch/x86/kvm/trace.h >> +++ b/arch/x86/kvm/trace.h >> @@ -62,21 +62,21 @@ TRACE_EVENT(kvm_hv_hypercall, >> TP_ARGS(code, fast, rep_cnt, rep_idx, ingpa, outgpa), >> >> TP_STRUCT__entry( >> - __field( __u16, code ) >> - __field( bool, fast ) >> __field( __u16, rep_cnt ) >> __field( __u16, rep_idx ) >> __field( __u64, ingpa ) >> __field( __u64, outgpa ) >> + __field( __u16, code ) >> + __field( bool, fast ) >> ), >> > > Looks like a pessimisation. > > Before: 24 bytes > After: 32 bytes > > (on a 64-bit machine, assuming no packing) This patch is predicated on packing the event structures. And since the ring buffer is 32-bit addressable, I don't attempt to improve alignment beyond 32-bit boundaries.
I don't understand this. Can you elaborate? What does "32-bit addressable" mean? And "predicated on packing the event structures"? Is the structure __attribute__((packed)), or is it not?
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