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SubjectRe: [PATCH 18/18] 2.6.17.9 perfmon2 patch for review: new x86_64 files
Christoph,

On Wed, Aug 23, 2006 at 04:25:55PM +0100, Christoph Hellwig wrote:
> On Wed, Aug 23, 2006 at 03:29:32AM -0700, Stephane Eranian wrote:
> > > > +#define PFM_EM64T_PEBS_SMPL_UUID { \
> > > > + 0x36, 0xbe, 0x97, 0x94, 0x1f, 0xbf, 0x41, 0xdf,\
> > > > + 0xb4, 0x63, 0x10, 0x62, 0xeb, 0x72, 0x9b, 0xad}
> > >
> > > What does it need the UUID for?
> > >
> > Every sampling format is identified by a UUID. This is how an
> > application can identify the format it wants to use when it
> > creates a context.
>
> Please use a string name, just like every other interface for
> such selections.

What are the advantages at the syscall level (i.e., copy_user,
format parsing) compared to a 16-entry byte array?

We are passing that uuid into a struct:

struct pfarg_ctx {
__u8 ctx_smpl_buf_id[16];
__u32 ctx_flags;
__s32 ctx_fd;
__u64 ctx_smpl_buf_size;
__u64 ctx_reserved3[12];
};

--
-Stephane
-
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