Re: [PATCH] linux/fs.h - Convert debug functions declared inline __attribute__((format (printf,x,y) to statement expression macros

[Joe Perches]

On Thu, 2008-02-28 at 11:23 +0100, Jan Hubicka wrote:
> The call ought to be always
> early inlined and not seen by any optimization pass.

The inlined functions don't actually appear in the generated code.

Look at the code generation differences for kernel/sched.c
function place_entity

$ size sched.inline.o sched.if0.o
   text    data     bss     dec     hex filename
  31385    2854     328   34567    8707 sched.inline.o
  31366    2854     328   34548    86f4 sched.if0.o

The current preprocessed only kernel/sched.i file contains:

# 612 "include/linux/device.h"
static inline __attribute__((always_inline)) int __attribute__ ((format 
(printf, 2, 3)))
dev_dbg(struct device *dev, const char *fmt, ...)
{
 return 0;
}
# 628 "include/linux/device.h"
static inline __attribute__((always_inline)) int __attribute__ ((format 
(printf, 2, 3)))
dev_vdbg(struct device *dev, const char *fmt, ...)
{
 return 0;
}

But the function place_entity doesn't use it directly or indirectly.
If the lines above are removed, the generated code for place_entity changes.

static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
        u64 vruntime;

        vruntime = cfs_rq->min_vruntime;

        if (sched_feat(TREE_AVG)) {
                struct sched_entity *last = __pick_last_entity(cfs_rq);
                if (last) {
                        vruntime += last->vruntime;
                        vruntime >>= 1;
                }
        } else if (sched_feat(APPROX_AVG) && cfs_rq->nr_running)
                vruntime += sched_vslice(cfs_rq)/2;

        /*
         * The 'current' period is already promised to the current tasks,
         * however the extra weight of the new task will slow them down a
         * little, place the new task so that it fits in the slot that
         * stays open at the end.
         */
        if (initial && sched_feat(START_DEBIT))
                vruntime += sched_vslice_add(cfs_rq, se);

        if (!initial) {
                /* sleeps upto a single latency don't count. */
                if (sched_feat(NEW_FAIR_SLEEPERS))
                        vruntime -= sysctl_sched_latency;

                /* ensure we never gain time by being placed backwards. */
                vruntime = max_vruntime(se->vruntime, vruntime);
        }

        se->vruntime = vruntime;
}