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sched : avoid changing cur_copy when a graph is already allocated #13922

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Merged
merged 1 commit into from
May 30, 2025
Merged

sched : avoid changing cur_copy when a graph is already allocated #13922

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15 changes: 10 additions & 5 deletions ggml/src/ggml-backend.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1340,7 +1340,10 @@ static bool ggml_backend_sched_alloc_splits(ggml_backend_sched_t sched) {
// allocate graph
if (backend_ids_changed || !ggml_gallocr_alloc_graph(sched->galloc, &sched->graph)) {
// the re-allocation may cause the split inputs to be moved to a different address
ggml_backend_sched_synchronize(sched);
// synchronize without ggml_backend_sched_synchronize to avoid changing cur_copy
for (int i = 0; i < sched->n_backends; i++) {
ggml_backend_synchronize(sched->backends[i]);
}
#ifndef NDEBUG
GGML_LOG_DEBUG("%s: failed to allocate graph, reserving (backend_ids_changed = %d)\n", __func__, backend_ids_changed);
#endif
Expand Down Expand Up @@ -1564,7 +1567,6 @@ bool ggml_backend_sched_alloc_graph(ggml_backend_sched_t sched, struct ggml_cgra

ggml_backend_sched_split_graph(sched, graph);


if (!ggml_backend_sched_alloc_splits(sched)) {
return false;
}
Expand Down Expand Up @@ -1598,9 +1600,12 @@ void ggml_backend_sched_synchronize(ggml_backend_sched_t sched) {
for (int i = 0; i < sched->n_backends; i++) {
ggml_backend_synchronize(sched->backends[i]);
}
// reset the current copy to 0 so that the graphs will be similar during generation
// necessary for CUDA graphs
sched->cur_copy = 0;
if (!sched->is_alloc) {
// if the graph is not already allocated, always use copy 0 after a synchronization
// this ensures that during generation the same copy is used every time,
// which avoids changes in the graph that could cause CUDA or other graphs to be disabled
sched->cur_copy = 0;
}
}

void ggml_backend_sched_set_eval_callback(ggml_backend_sched_t sched, ggml_backend_sched_eval_callback callback, void * user_data) {
Expand Down
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