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SubjectRe: [RFC PATCH v2 3/5] sched: make schedstats helper independent of cfs_rq
On Mon, Nov 23, 2020 at 08:58:06PM +0800, Yafang Shao wrote:
> The 'cfs_rq' in these helpers
> update_stats_{wait_start, wait_end, enqueue_sleeper} is only used to get
> the rq_clock, so we can pass the rq directly. Then these helpers can be
> used by all sched class after being moved into stats.h.
>
> After that change, the size of vmlinux is increased around 824Bytes.
> w/o this patch, with this patch
> Size of vmlinux: 78443832 78444656
>
> Signed-off-by: Yafang Shao <laoar.shao@gmail.com>

The inline helpers are quite large. When I was suggesting that the overhead
was minimal, what I expected what that the inline functions would be a
schedstat_enabled() followed by a real function call. It would introduce
a small additional overhead when schedstats are enabled but avoid vmlinux
growing too large

e.g.

static inline void
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
if (!schedstat_enabled())
return;

__update_stats_wait_start(cfs_rq, se);
}

where __update_stats_wait_start then lives in kernel/sched/stats.c

--
Mel Gorman
SUSE Labs

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