ikawrakow/ik_llama.cpp
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Reduce back-end syncs (#1049)

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* Reduce backend synchronization calls

* Also this

---------

Co-authored-by: Iwan Kawrakow <iwan.kawrakow@gmail.com>
This commit is contained in:
Kawrakow
2025-12-11 07:04:44 +01:00
committed by GitHub
parent e61cd0303a
commit 02206cff46
1 changed files with 33 additions and 13 deletions
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46
ggml/src/ggml-backend.cpp
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@@ -12,6 +12,7 @@
#include <string>
#include <vector>
#include <set>
#include <array>
#define IK_PRINT_TIMING 0
@@ -1879,6 +1880,8 @@ static enum ggml_status ggml_backend_sched_compute_splits(ggml_backend_sched_t s
std::vector<uint32_t> unique_ids;
ggml_tensor * last_ids_tensor = nullptr;
std::array<bool, GGML_SCHED_MAX_BACKENDS> needs_sync{{true}};
for (int i = 0; i < sched->n_splits; i++) {
#if IK_PRINT_TIMING
int64_t tim1 = ggml_time_us();
@@ -1897,18 +1900,24 @@ static enum ggml_status ggml_backend_sched_compute_splits(ggml_backend_sched_t s
if (input->flags & GGML_TENSOR_FLAG_INPUT) {
// inputs from the user must be copied immediately to prevent the user overwriting the data before the copy is done
if (sched->events[split_backend_id][sched->cur_copy] != NULL) {
ggml_backend_event_synchronize(sched->events[split_backend_id][sched->cur_copy]);
} else {
ggml_backend_synchronize(split_backend);
if (needs_sync[split_backend_id]) {
if (sched->events[split_backend_id][sched->cur_copy] != NULL) {
ggml_backend_event_synchronize(sched->events[split_backend_id][sched->cur_copy]);
} else {
ggml_backend_synchronize(split_backend);
}
needs_sync[split_backend_id] = false;
}
ggml_backend_tensor_copy(input, input_cpy);
} else {
// wait for the split backend to finish using the input before overwriting it
if (sched->events[split_backend_id][sched->cur_copy] != NULL) {
ggml_backend_event_wait(split_backend, sched->events[split_backend_id][sched->cur_copy]);
} else {
ggml_backend_synchronize(split_backend);
if (needs_sync[split_backend_id]) {
if (sched->events[split_backend_id][sched->cur_copy] != NULL) {
ggml_backend_event_wait(split_backend, sched->events[split_backend_id][sched->cur_copy]);
} else {
ggml_backend_synchronize(split_backend);
}
needs_sync[split_backend_id] = false;
}
ggml_tensor * node = split->graph.nodes[0];
@@ -1944,6 +1953,7 @@ static enum ggml_status ggml_backend_sched_compute_splits(ggml_backend_sched_t s
ggml_backend_tensor_get_async(ids_backend, ids_tensor, ids.data(), 0, ggml_nbytes(ids_tensor));
ggml_backend_synchronize(ids_backend);
needs_sync[tensor_backend_id(ids_tensor)] = false;
unique_ids.resize((n_expert + 31)/32);
std::memset(unique_ids.data(), 0, unique_ids.size()*sizeof(uint32_t));
@@ -2000,17 +2010,27 @@ static enum ggml_status ggml_backend_sched_compute_splits(ggml_backend_sched_t s
// try async copy, but if not possible, we can still use a sync copy without synchronizing the dst backend, since we handle the synchronization here with multiple copies and events
// TODO: add public function to facilitate this, since applications do not have direct access to the backend interface
if (!split_backend->iface.cpy_tensor_async || !split_backend->iface.cpy_tensor_async(input_backend, split_backend, input, input_cpy)) {
ggml_backend_synchronize(input_backend);
if (sched->events[split_backend_id][sched->cur_copy] != NULL) {
ggml_backend_event_synchronize(sched->events[split_backend_id][sched->cur_copy]);
} else {
ggml_backend_synchronize(split_backend);
int input_backend_id = tensor_backend_id(input);
if (needs_sync[input_backend_id]) {
ggml_backend_synchronize(input_backend);
needs_sync[input_backend_id] = false;
}
if (needs_sync[split_backend_id]) {
if (sched->events[split_backend_id][sched->cur_copy] != NULL) {
ggml_backend_event_synchronize(sched->events[split_backend_id][sched->cur_copy]);
} else {
ggml_backend_synchronize(split_backend);
}
needs_sync[split_backend_id] = false;
}
ggml_backend_tensor_copy(input, input_cpy);
}
}
}
if (split->n_inputs > 0) {
needs_sync[split_backend_id] = true;
}
if (!sched->callback_eval) {
#if IK_PRINT_TIMING
int64_t tim2 = ggml_time_us();