On Wed, Jan 18, 2017 at 11:44:11AM -0700, Jason Gunthorpe wrote:
> On Wed, Jan 18, 2017 at 08:31:04PM +0200, Leon Romanovsky wrote:
> > On Wed, Jan 18, 2017 at 09:44:44AM -0700, Jason Gunthorpe wrote:
> > > On Wed, Jan 18, 2017 at 07:31:30AM +0200, Leon Romanovsky wrote:
> > > > > +#define PRINT_ERR(fmt, ...) \
> > > > > +do { \
> > > > > + fprintf(stderr, "[%s:%d]" fmt, __func__, __LINE__, ##__VA_ARGS__); \
> > > > > +} while (0)
> > > > > +
> > > > > +#define PRINT_DBG(dbg_mask, dbg_level, fmt, ...) \
> > > > > +do { \
> > > > > + if ((rdma_dbg_mask & dbg_mask) && (rdma_dbg_level >= dbg_level)) \
> > > > > + fprintf(stderr, "[%s:%d]" fmt, __func__, __LINE__, ##__VA_ARGS__); \
> > > > > +} while (0)
> > > > > +
> > > > > +#define LOG_DBG(dbg_fp, dbg_mask, dbg_level, fmt, ...) \
> > > > > +do { \
> > > > > + if ((rdma_dbg_mask & dbg_mask) && (rdma_dbg_level >= dbg_level)) \
> > > > > + fprintf(dbg_fp, "[%s:%d]" fmt, __func__, __LINE__, ##__VA_ARGS__); \
> > > > > +} while (0)
> > > > > +
> > > > > +#define LOG_DBG_FLUSH(dbg_fp, dbg_mask, dbg_level, fmt, ...) \
> > > > > +do { \
> > > > > + LOG_DBG(dbg_fp, dbg_mask, dbg_level, fmt, ##__VA_ARGS__); \
> > > > > + if (dbg_fp != stderr) \
> > > > > + fflush(dbg_fp); \
> > > > > +} while (0)
> > > >
> > > > IMHO, these macros should be inline functions, and better to avoid global variables.
> > >
> > > It is more expensive at the call site to inline something that calls
> > > via va_args than via ..., so these should remain as macros.
> >
> > These macros/functions need to be compiled in for DEBUG mode only, in
> > such case you can pay extra CPU cycles.
>
> One of the reasonable ways to use this is to always compile in *error
> case* debug prints, as these are intrinsically on the slow error path
> already - however for that use we certainly want to minimize icache
> consumption at the call site.
There are debug prints in data path too.
https://patchwork.kernel.org/patch/9521817/
See mlx5_get_next_cqe and mlx5_cq_read_wc_opcode functions.
>
> If we don't want to micro-optimize the DEBUG enabled case then I
> recommend this approach for the macro:
>
> #define LOG_DBG(dbg_fp, dbg_mask, dbg_level, fmt, ...)
> ({
> static const struct verbs_log_loc loc = {
> .dbg_mask = dbg_mask,
> .dbg_level = dbg_level,
> .fmt = fmt,
> .line = __LINE__,
> .func = __func__ };
> __check_fmt_args(fmt, ## __VA_ARGS__);
> verbs_log_dbg(dbg_fp, &loc, ## __VA_ARGS__);
> })
>
> verbs_log_dbg would be implemented out of line.
>
> That has the lowest call-site icache overhead as most of the required
> data is pushed into the .rodata pointer (instead of in .text) and we
> can continue to use the register calling convention for the va_args.
>
> We can probably also eliminate dbg_fp as an argument, there is no
> reason to have the providers store that, IHMO.
>
> Jason
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