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Merge pull request #446 from cdhdt/perf/io-direct-pilot

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io: skip the wasted WILLNEED on expert weights under DIRECT=1 (#441 safe half)
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Vincenzo Fornaro
2026-07-20 18:11:26 +02:00
committed by GitHub
parent 04ed0049a4 85107f8ce6
commit c98b451738
1 changed files with 11 additions and 2 deletions
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c/colibri.c
+11 -2
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@@ -1789,12 +1789,21 @@ static void expert_host_ensure(Model *m, int layer, ESlot *s){
#endif
/* prefetch asincrono dei pesi di un expert (e delle sue scale .qs): avvia il readahead
* cosi' le letture sincrone successive trovano la page-cache calda. */
* cosi' le letture sincrone successive trovano la page-cache calda.
* Sotto g_direct i PESI vengono letti con O_DIRECT (bypassa la page-cache, vedi
* expert_load): il WILLNEED su di essi scalda pagine che la lettura di domanda non
* consuma -> readahead sprecato sul disco, la risorsa piu' scarsa nello streaming.
* Le scale .qs restano SEMPRE bufferizzate (pread sul fd normale), quindi il loro
* WILLNEED resta utile anche con DIRECT=1. fadvise e' solo consultivo: saltarlo non
* cambia mai l'output (bit-identico), riduce solo I/O sprecato.
* EN: under O_DIRECT the weights bypass the page cache, so their WILLNEED is wasted;
* the .qs scales are always buffered, so keep theirs. Advisory hint -> output-preserving. */
static void expert_prefetch(Model *m, int layer, int eid){
char nm[300];
const char *suf[3]={"gate_proj.weight","up_proj.weight","down_proj.weight"};
for(int k=0;k<3;k++){
snprintf(nm,sizeof(nm),"model.layers.%d.mlp.experts.%d.%s",layer,eid,suf[k]); st_prefetch(&m->S,nm);
snprintf(nm,sizeof(nm),"model.layers.%d.mlp.experts.%d.%s",layer,eid,suf[k]);
if(!g_direct) st_prefetch(&m->S,nm);
char qs[320]; snprintf(qs,sizeof(qs),"%s.qs",nm); st_prefetch(&m->S,qs);
}
}