Re: [Xen-devel] [RFC][PATCH] 1/3] [XEN] Use explicit bit sized fields for exported xentrace data.

["George Dunlap " <dunlapg@xxxxxxxxx>]

Hmm... this has the unfortunate side-effect of doubling the size of
the trace, and effectively halving the effectiveness of the trace
buffer in avoiding drops.  My moderate-length traces are already in
the gigabyte range, and I occasionally lose trace records even with a
buffer size of 256.  It would be really nice if we could avoid that.

I happen to be using the VMENTER/VMEXIT tracing, which could be
consolidated into one record if we went to a 64-bit trace.  Is anyone
else doing high-bandwidth tracing that this would affect in a
significantly negative way?

-George

On 11/30/06, Tony Breeds <tony@xxxxxxxxxxxxxxxxxx> wrote:
> Signed-off-by: Tony Breeds <tony@xxxxxxxxxxxxxxxxxx>
> ---
>
>  xen/common/trace.c         |    6 +++---
>  xen/include/public/trace.h |    2 +-
>  xen/include/xen/trace.h    |   14 +++++++-------
>  3 files changed, 11 insertions(+), 11 deletions(-)
>
> Index: xen-unstable.hg-mainline.xentrace/xen/common/trace.c
> ===================================================================
> --- xen-unstable.hg-mainline.xentrace.orig/xen/common/trace.c
> +++ xen-unstable.hg-mainline.xentrace/xen/common/trace.c
> @@ -46,7 +46,7 @@ static int nr_recs;
>  static int t_buf_highwater;
>
>  /* Number of records lost due to per-CPU trace buffer being full. */
> -static DEFINE_PER_CPU(unsigned long, lost_records);
> +static DEFINE_PER_CPU(uint64_t, lost_records);
>
>  /* a flag recording whether initialization has been done */
>  /* or more properly, if the tbuf subsystem is enabled right now */
> @@ -228,8 +228,8 @@ int tb_control(xen_sysctl_tbuf_op_t *tbc
>   * failure, otherwise 0.  Failure occurs only if the trace buffers are not yet
>   * initialised.
>   */
> -void trace(u32 event, unsigned long d1, unsigned long d2,
> -           unsigned long d3, unsigned long d4, unsigned long d5)
> +void trace(uint32_t event, uint64_t d1, uint64_t d2, uint64_t d3, uint64_t d4,
> +                           uint64_t d5)
>  {
>      struct t_buf *buf;
>      struct t_rec *rec;
> Index: xen-unstable.hg-mainline.xentrace/xen/include/public/trace.h
> ===================================================================
> --- xen-unstable.hg-mainline.xentrace.orig/xen/include/public/trace.h
> +++ xen-unstable.hg-mainline.xentrace/xen/include/public/trace.h
> @@ -76,7 +76,7 @@
>  struct t_rec {
>      uint64_t cycles;          /* cycle counter timestamp */
>      uint32_t event;           /* event ID                */
> -    unsigned long data[5];    /* event data items        */
> +    uint64_t data[5];         /* event data items        */
>  };
>
>  /*
> Index: xen-unstable.hg-mainline.xentrace/xen/include/xen/trace.h
> ===================================================================
> --- xen-unstable.hg-mainline.xentrace.orig/xen/include/xen/trace.h
> +++ xen-unstable.hg-mainline.xentrace/xen/include/xen/trace.h
> @@ -33,19 +33,19 @@ void init_trace_bufs(void);
>  /* used to retrieve the physical address of the trace buffers */
>  int tb_control(struct xen_sysctl_tbuf_op *tbc);
>
> -void trace(u32 event, unsigned long d1, unsigned long d2,
> -           unsigned long d3, unsigned long d4, unsigned long d5);
> +void trace(uint32_t event, uint64_t d1, uint64_t d2, uint64_t d3, uint64_t d4,
> +                           uint64_t d5);
>
>  /* Avoids troubling the caller with casting their arguments to a trace macro */
>  #define trace_do_casts(e,d1,d2,d3,d4,d5) \
>      do {                                 \
>          if ( unlikely(tb_init_done) )    \
>              trace(e,                     \
> -                 (unsigned long)d1,      \
> -                 (unsigned long)d2,      \
> -                 (unsigned long)d3,      \
> -                 (unsigned long)d4,      \
> -                 (unsigned long)d5);     \
> +                 (uint64_t)d1,           \
> +                 (uint64_t)d2,           \
> +                 (uint64_t)d3,           \
> +                 (uint64_t)d4,           \
> +                 (uint64_t)d5);          \
>      } while ( 0 )
>
>  /* Convenience macros for calling the trace function. */
>
>
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