Re: [Qemu-devel] RFC: Design Doc for a new trace format (to support variable number/size of args per event) simpletrace-v2

[Markus Armbruster]

Stefan Hajnoczi <address@hidden> writes:

[...]
> So forget I said "self-describing" :).  I think the only changes from
> the v1 format we need are:
>
> 1. New magic number to mark v2 format.
>
> 2. Trace records are no longer fixed-length, they include a size field:
>
> typedef struct {
>     uint32_t length; /* in bytes */
>     uint32_t reserved; /* unused */
>     uint64_t event;
>     uint64_t timestamp_ns;
>     uint8_t arguments[];
> } TraceRecord;
>
> 3. Strings are serialized like this:
>
> uint16_t length;
> char chars[length];

16 bit length?  Sure you want that?

> These changes enable:
>
> 1. Variable number of trace event arguments.
>
> 2. Variable-length strings.

Byte strings, i.e. zero bytes not special.