ggml: Support heterogeneous KV cache layer sizes in memory estimation

Gemma3 uses sliding windows for its context on 5/6 layers, significantly
reducing memory usage but leading to uneven usage across layers,
which makes allocation to the correct GPU difficult. We currently
estimate very conservatively by assuming all layers are consistent
at the max size.

Llama3.2-vision is also inconsistent between self attention and cross
attention layers - at moment, we calculate the correct total size
and then average this across layers. In some cases, this may lead
to crashes if a large layer is placed on a GPU sized by the average.

This allows memory estimation to calculate per-layer KV cache size
and take this account when placing layers onto GPUs. We already do
this for weights that vary per-tensor, so this is a logical extension.

Fixes #9730
Fixes #9890
This commit is contained in:
Jesse Gross
2025-03-24 13:39:07 -07:00
committed by Jesse Gross
parent f4f0992b6e
commit f66216e399
5 changed files with 49 additions and 28 deletions

View File

@@ -15,12 +15,12 @@ import (
)
// This algorithm looks for a complete fit to determine if we need to unload other models
func PredictServerFit(allGpus discover.GpuInfoList, f *ggml.GGML, adapters, projectors []string, opts api.Options) (bool, uint64) {
func PredictServerFit(allGpus discover.GpuInfoList, f *ggml.GGML, adapters, projectors []string, opts api.Options, numParallel int) (bool, uint64) {
// Split up the GPUs by type and try them
var estimatedVRAM uint64
for _, gpus := range allGpus.ByLibrary() {
var layerCount int
estimate := EstimateGPULayers(gpus, f, projectors, opts)
estimate := EstimateGPULayers(gpus, f, projectors, opts, numParallel)
layerCount, estimatedVRAM = estimate.Layers, estimate.VRAMSize
if opts.NumGPU < 0 {
if layerCount > 0 && layerCount >= int(f.KV().BlockCount()+1) {
@@ -71,7 +71,7 @@ type MemoryEstimate struct {
// Given a model and one or more GPU targets, predict how many layers and bytes we can load, and the total size
// The GPUs provided must all be the same Library
func EstimateGPULayers(gpus []discover.GpuInfo, f *ggml.GGML, projectors []string, opts api.Options) MemoryEstimate {
func EstimateGPULayers(gpus []discover.GpuInfo, f *ggml.GGML, projectors []string, opts api.Options, numParallel int) MemoryEstimate {
// Graph size for a partial offload, applies to all GPUs
var graphPartialOffload uint64
@@ -137,13 +137,19 @@ func EstimateGPULayers(gpus []discover.GpuInfo, f *ggml.GGML, projectors []strin
}
}
kv, graphPartialOffload, graphFullOffload := f.GraphSize(uint64(opts.NumCtx), uint64(min(opts.NumCtx, opts.NumBatch)), kvct)
kv, graphPartialOffload, graphFullOffload := f.GraphSize(uint64(opts.NumCtx), uint64(min(opts.NumCtx, opts.NumBatch)), numParallel, kvct)
// KV is proportional to the number of layers
layerSize += kv / f.KV().BlockCount()
if len(kv) > 0 {
layerSize += kv[0]
}
var kvTotal uint64
for _, kvLayer := range kv {
kvTotal += kvLayer
}
if graphPartialOffload == 0 {
graphPartialOffload = f.KV().GQA() * kv / 6
graphPartialOffload = f.KV().GQA() * kvTotal / 6
}
if graphFullOffload == 0 {
graphFullOffload = graphPartialOffload
@@ -217,7 +223,7 @@ func EstimateGPULayers(gpus []discover.GpuInfo, f *ggml.GGML, projectors []strin
// Some models have inconsistent layer sizes
if blk, ok := layers[fmt.Sprintf("blk.%d", i)]; ok {
layerSize = blk.Size()
layerSize += kv / f.KV().BlockCount()
layerSize += kv[i]
memoryWeights += blk.Size()
}
@@ -315,7 +321,7 @@ func EstimateGPULayers(gpus []discover.GpuInfo, f *ggml.GGML, projectors []strin
layersRequested: opts.NumGPU,
layersModel: int(f.KV().BlockCount()) + 1,
availableList: availableList,
kv: kv,
kv: kvTotal,
allocationsList: allocationsList,
memoryWeights: memoryWeights,
memoryLayerOutput: memoryLayerOutput,