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llama : KV cache view API + better KV cache management #4170

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merged 4 commits into from
Nov 23, 2023
Merged

llama : KV cache view API + better KV cache management #4170

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79cb8f0
llama : keep track of used KV cells + better KV cache management
ggerganov Nov 22, 2023
671f639
llama : zero KV cache used upon clear
ggerganov Nov 22, 2023
5df7d06
llama : allow exporting a view of the KV cache (#4180)
KerfuffleV2 Nov 23, 2023
f8e9f11
common : add -dkvc arg for enabling kv cache dumps
ggerganov Nov 23, 2023
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39 changes: 35 additions & 4 deletions llama.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1280,6 +1280,7 @@ struct llama_kv_cache {
// cannot be freely changed after a slot has been allocated.
uint32_t head = 0;
uint32_t size = 0;
uint32_t used = 0; // used cells (i.e. at least one seq_id)

// computed before each graph build
uint32_t n = 0;
Expand Down Expand Up @@ -1504,6 +1505,7 @@ static bool llama_kv_cache_init(

cache.head = 0;
cache.size = n_ctx;
cache.used = 0;

cache.cells.clear();
cache.cells.resize(n_ctx);
Expand Down Expand Up @@ -1605,6 +1607,8 @@ static bool llama_kv_cache_find_slot(
}
}

cache.used += n_tokens;

return true;
}

Expand All @@ -1625,6 +1629,7 @@ static void llama_kv_cache_clear(struct llama_kv_cache & cache) {
cache.cells[i].seq_id.clear();
}
cache.head = 0;
cache.used = 0;
}

static void llama_kv_cache_seq_rm(
Expand All @@ -1647,14 +1652,17 @@ static void llama_kv_cache_seq_rm(
continue;
}
if (cache.cells[i].seq_id.empty()) {
// keep count of the number of used cells
if (cache.cells[i].pos >= 0) cache.used--;

cache.cells[i].pos = -1;
if (new_head == cache.size) new_head = i;
}
}
}

// If we freed up a slot, set head to it so searching can start there.
if (new_head != cache.size) cache.head = new_head;
if (new_head != cache.size && new_head < cache.head) cache.head = new_head;
}

static void llama_kv_cache_seq_cp(
Expand All @@ -1680,6 +1688,7 @@ static void llama_kv_cache_seq_keep(struct llama_kv_cache & cache, llama_seq_id

for (uint32_t i = 0; i < cache.size; ++i) {
if (!cache.cells[i].has_seq_id(seq_id)) {
if (cache.cells[i].pos >= 0) cache.used--;
cache.cells[i].pos = -1;
cache.cells[i].seq_id.clear();
if (new_head == cache.size) new_head = i;
Expand All @@ -1690,7 +1699,7 @@ static void llama_kv_cache_seq_keep(struct llama_kv_cache & cache, llama_seq_id
}

// If we freed up a slot, set head to it so searching can start there.
if (new_head != cache.size) cache.head = new_head;
if (new_head != cache.size && new_head < cache.head) cache.head = new_head;
}

static void llama_kv_cache_seq_shift(
Expand All @@ -1711,6 +1720,7 @@ static void llama_kv_cache_seq_shift(
cache.cells[i].delta += delta;

if (cache.cells[i].pos < 0) {
if (!cache.cells[i].seq_id.empty()) cache.used--;
cache.cells[i].pos = -1;
cache.cells[i].seq_id.clear();
if (new_head == cache.size) new_head = i;
Expand Down Expand Up @@ -5469,6 +5479,12 @@ static int llama_decode_internal(
batch.seq_id = seq_id_arr.data();
}

// if we have enough unused cells before the current head ->
// better to start searching from the beginning of the cache, hoping to fill it
if (kv_self.head > kv_self.used + 2*n_tokens) {
kv_self.head = 0;
}

if (!llama_kv_cache_find_slot(kv_self, batch)) {
return 1;
}
Expand All @@ -5479,7 +5495,7 @@ static int llama_decode_internal(
//kv_self.n = std::max(32, GGML_PAD(llama_kv_cache_cell_max(kv_self), 32)); // TODO: this might be better for CUDA?
kv_self.n = std::min((int32_t) cparams.n_ctx, std::max(32, llama_kv_cache_cell_max(kv_self)));

//printf("kv_self.n = %d\n", kv_self.n);
//printf("kv_self.n = %5d, kv_self.used = %5d, kv_self.head = %5d\n", kv_self.n, kv_self.used, kv_self.head);

ggml_allocr_reset(lctx.alloc);

Expand Down Expand Up @@ -8790,7 +8806,17 @@ int llama_model_apply_lora_from_file(const struct llama_model * model, const cha
}

int llama_get_kv_cache_token_count(const struct llama_context * ctx) {
return ctx->kv_self.head;
int result = 0;

for (uint32_t i = 0; i < ctx->kv_self.size; i++) {
result += ctx->kv_self.cells[i].seq_id.size();
}

return result;
}

int llama_get_kv_cache_used_cells(const struct llama_context * ctx) {
return ctx->kv_self.used;
}

void llama_kv_cache_clear(struct llama_context * ctx) {
Expand Down Expand Up @@ -8960,10 +8986,12 @@ static void llama_copy_state_data_internal(struct llama_context * ctx, llama_dat
const size_t kv_buf_size = kv_self.buf.size;
const uint32_t kv_head = kv_self.head;
const uint32_t kv_size = kv_self.size;
const uint32_t kv_used = kv_self.used;

data_ctx->write(&kv_buf_size, sizeof(kv_buf_size));
data_ctx->write(&kv_head, sizeof(kv_head));
data_ctx->write(&kv_size, sizeof(kv_size));
data_ctx->write(&kv_used, sizeof(kv_used));

if (kv_buf_size) {
const size_t elt_size = ggml_element_size(kv_self.k);
Expand Down Expand Up @@ -9086,10 +9114,12 @@ size_t llama_set_state_data(struct llama_context * ctx, uint8_t * src) {
size_t kv_buf_size;
uint32_t kv_head;
uint32_t kv_size;
uint32_t kv_used;

memcpy(&kv_buf_size, inp, sizeof(kv_buf_size)); inp += sizeof(kv_buf_size);
memcpy(&kv_head, inp, sizeof(kv_head)); inp += sizeof(kv_head);
memcpy(&kv_size, inp, sizeof(kv_size)); inp += sizeof(kv_size);
memcpy(&kv_used, inp, sizeof(kv_used)); inp += sizeof(kv_used);

if (kv_buf_size) {
GGML_ASSERT(kv_self.buf.size == kv_buf_size);
Expand Down Expand Up @@ -9124,6 +9154,7 @@ size_t llama_set_state_data(struct llama_context * ctx, uint8_t * src) {

ctx->kv_self.head = kv_head;
ctx->kv_self.size = kv_size;
ctx->kv_self.used = kv_used;

ctx->kv_self.cells.resize(kv_size);

Expand Down
9 changes: 6 additions & 3 deletions llama.h
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Original file line number Diff line number Diff line change
Expand Up @@ -361,9 +361,12 @@ extern "C" {
// KV cache
//

// Returns the number of tokens in the KV cache
LLAMA_API DEPRECATED(int llama_get_kv_cache_token_count(const struct llama_context * ctx),
"avoid using this, it will be removed in the future, instead - count the tokens in user code");
// Returns the number of tokens in the KV cache (slow, use only for debug)
// If a KV cell has multiple sequences assigned to it, it will be counted multiple times
LLAMA_API int llama_get_kv_cache_token_count(const struct llama_context * ctx);

// Returns the number of used KV cells (i.e. have at least one sequence assigned to them)
LLAMA_API int llama_get_kv_cache_used_cells(const struct llama_context * ctx);

// Clear the KV cache
LLAMA_API void llama_kv_cache_clear(
Expand Down
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