Messages in this thread | | | Date | Mon, 26 Aug 2013 13:46:46 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH 04/10] sched, fair: Shrink sg_lb_stats and play memset games |
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On Sat, Aug 24, 2013 at 03:15:57AM -0700, Paul Turner wrote: > > +static inline void init_sd_lb_stats(struct sd_lb_stats *sds) > > +{ > > + /* > > + * struct sd_lb_stats { > > + * struct sched_group * busiest; // 0 8 > > + * struct sched_group * this; // 8 8 > > + * long unsigned int total_load; // 16 8 > > + * long unsigned int total_pwr; // 24 8 > > + * long unsigned int avg_load; // 32 8 > > + * struct sg_lb_stats { > > + * long unsigned int avg_load; // 40 8 > > + * long unsigned int group_load; // 48 8 > > + * ... > > + * } busiest_stat; // 40 56 > > + * struct sg_lb_stats this_stat; // 96 56 > > + * > > + * // size: 152, cachelines: 3, members: 7 > > + * // last cacheline: 24 bytes > > + * }; > > + * > > + * Skimp on the clearing to avoid duplicate work. We can avoid clearing > > + * this_stat because update_sg_lb_stats() does a full clear/assignment. > > + * We must however clear busiest_stat::avg_load because > > + * update_sd_pick_busiest() reads this before assignment. > > + */ > > Does gcc seriously not get this right if we just write: > sds->busiest = NULL; > sds->local = NULL; > .... > > etc.?
There's a thought ;-) How about something like this?
sds = (struct sd_lb_stats){ .busiest = NULL, .local = NULL,
.busiest_stat = { .avg_load = 0, }, };
C99 named initializers should ignore all unmentioned fields, and I think we don't actually touch any of the other fields unless something is set.
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