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llama : optimize defrag moves + fix fragmentation calculation (#6037)

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* attempt to reduce the impact of a worst-case scenario

* fragmentation calculation fix

* Update llama.cpp

---------

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>
This commit is contained in:
Michael Podvitskiy 2024-03-14 11:56:48 +01:00 committed by GitHub
parent 3ca23481dd
commit 2c4fb69246
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1 changed files with 19 additions and 11 deletions
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llama.cpp
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@ -9036,8 +9036,8 @@ static int llama_decode_internal(
//llama_synchronize(&lctx);
// decide if we need to defrag the kv cache
if (cparams.defrag_thold >= 0.0f) {
const float fragmentation = kv_self.n >= 128 ? 1.0f - float(kv_self.used + n_tokens_all)/float(kv_self.n) : 0.0f;
if (cparams.causal_attn && cparams.defrag_thold >= 0.0f) {
const float fragmentation = kv_self.n >= 128 ? 1.0f - float(kv_self.used)/float(kv_self.n) : 0.0f;
// queue defragmentation for next llama_kv_cache_update
if (fragmentation > cparams.defrag_thold) {
@ -9069,6 +9069,11 @@ static void llama_kv_cache_defrag_internal(struct llama_context & lctx) {
// number of cells moved
uint32_t n_moves = 0;
// each move requires 6*n_layer tensors (see build_defrag)
// - source view, destination view, copy operation
// - x2 for keys and values
const uint32_t max_moves = LLAMA_MAX_NODES/(6*n_layer);
// determine which KV cells to move where
//
// cell i moves to ids[i]
@ -9095,15 +9100,6 @@ static void llama_kv_cache_defrag_internal(struct llama_context & lctx) {
nh++;
}
// each move requires 6*n_layer tensors (see build_defrag)
// - source view, destination view, copy operation
// - x2 for keys and values
//
if (6*(n_moves + nh)*n_layer >= LLAMA_MAX_NODES) {
// the graph is too big, we cannot move more cells
break;
}
uint32_t nf = 0;
uint32_t is = n_kv - 1;
@ -9133,11 +9129,19 @@ static void llama_kv_cache_defrag_internal(struct llama_context & lctx) {
// are we moving a continuous block of memory?
bool cont = false;
// should we stop searching for the next move?
bool stop = false;
// go back and move the nf cells to the hole
for (; i1 < n_kv; ++i1) {
auto & cell1 = kv_self.cells[i1];
if (cell1.is_empty() || ids[i1] != n_kv) {
if (n_moves == max_moves) {
stop = true;
break;
}
cont = false;
continue;
}
@ -9164,6 +9168,10 @@ static void llama_kv_cache_defrag_internal(struct llama_context & lctx) {
}
}
if (stop || n_moves == max_moves) {
break;
}
//LLAMA_LOG_INFO("(tmp log) KV defrag: move [%u, %u) to [%u, %u)\n", is, i1 + 1, i0, i0 + nh);
i0 += nh - 1;