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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,78 @@ | ||
| #ifndef HEADER_fd_src_ballet_pack_fd_pack_pacing_h | ||
| #define HEADER_fd_src_ballet_pack_fd_pack_pacing_h | ||
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| /* One of the keys to packing well is properly pacing CU consumption. | ||
| Without pacing, pack will end up filling the block with non-ideal | ||
| transactions. Since at the current limits, the banks can execute a | ||
| block worth of CUs in a fraction of the block time, without pacing, | ||
| any lucrative transactions that arrive at towards the end of a block | ||
| will have to be delayed until the next block (or another leader's | ||
| block if it's the last in our rotation). */ | ||
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| struct fd_pack_pacing_private { | ||
| /* Start and end time of block in ticks */ | ||
| long t_start; | ||
| long t_end; | ||
| /* Number of CUs in the block */ | ||
| ulong max_cus; | ||
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| ulong home_stretch_cutoff; /* in CUs, where the slope switches */ | ||
| float raw_slope; /* in ticks per CU */ | ||
| float offset; /* in ticks */ | ||
| }; | ||
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| typedef struct fd_pack_pacing_private fd_pack_pacing_t; | ||
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| /* fd_pack_pacing_init begins pacing for a slot which starts at now and | ||
| ends at t_end (both measured in fd_tickcount() space) and will | ||
| contain cus CUs. cus in (0, 2^32). t_end - t_start should be about | ||
| 400ms or less, but must be in (0, 2^32) as well. */ | ||
| static inline void | ||
| fd_pack_pacing_init( fd_pack_pacing_t * pacer, | ||
| long t_start, | ||
| long t_end, | ||
| ulong max_cus ) { | ||
| /* The exact style of pacing needs to be the subject of quantitative | ||
| experimentation, so for now we're just doing something that passes | ||
| the gut check. We'll pace for 90% of the CUs through the first 75% | ||
| of the block time, and then the last 10% through the last 25% of the | ||
| block time. This gives us pretty good tolerance against transactions | ||
| taking longer to execute than we expect (the extreme of which being | ||
| transactions that fail to land). */ | ||
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| pacer->t_start = t_start; | ||
| pacer->t_end = t_end; | ||
| pacer->max_cus = max_cus; | ||
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| pacer->raw_slope = (float)(t_end - t_start)/(float)max_cus; | ||
| pacer->offset = 1.5f * (float)(t_end - t_start); /* the math works out to be 1.5x */ | ||
| pacer->home_stretch_cutoff = (max_cus*9UL + 4UL)/10UL; | ||
| } | ||
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| /* fd_pack_pacing_next returns the time (in fd_tickcount() space) at | ||
| which the next attempt should be made to schedule transactions. | ||
| The returned value will typically be between t_start and t_end, but | ||
| may be slightly out of range due to rounding or if consumed_cus is | ||
| larger than the max cu value provided in fd_pack_pacing_init. | ||
| consumed_cus need not increase monotonically between calls. | ||
| now should be the time at which the consumed_cus was measured. It's | ||
| not used right now, but is provided to allow for more sophisticated | ||
| implementations in the future. | ||
| fd_pack_pacing_init must have been called prior to the first call of | ||
| fd_pack_pacing_next. */ | ||
| static inline long | ||
| fd_pack_pacing_next( fd_pack_pacing_t * pacer, | ||
| ulong consumed_cus, | ||
| long now ) { | ||
| (void)now; | ||
| int non_home_stretch = consumed_cus < pacer->home_stretch_cutoff; | ||
| return pacer->t_start + (long)( (float)consumed_cus * pacer->raw_slope * fd_float_if( non_home_stretch, 0.75f/0.9f, 0.25f/0.1f ) | ||
| - fd_float_if( non_home_stretch, 0.0f, pacer->offset )); | ||
| } | ||
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| #endif /* HEADER_fd_src_ballet_pack_fd_pack_pacing_h */ |