gpu/internal/vulkan,internal/vk: allocate descriptor sets in batches

We know exactly the configuration and number of sets in each pool, so
we may as well allocate them al up front.

References: https://todo.sr.ht/~eliasnaur/gio/375
Signed-off-by: Elias Naur <mail@eliasnaur.com>

gpu/internal/vulkan/vulkan.go

@@ -107,8 +107,8 @@ type descPool struct {
 	layout     vk.PipelineLayout
 	descLayout vk.DescriptorSetLayout
 	pool       vk.DescriptorPool
+	sets       []vk.DescriptorSet
 	size       int
-	cap        int
 	texBinds   []int
 	imgBinds   []int
 	bufBinds   []int
@@ -224,7 +224,6 @@ func (b *Backend) resetPipes() {
 			continue
 		}
 		if p.desc.size > 0 {
-			vk.ResetDescriptorPool(b.dev, p.desc.pool)
 			p.desc.size = 0
 		}
 	}
@@ -686,24 +685,17 @@ func (p *descPool) release(d vk.Device) {
 }
 
 func (p *descPool) bindDescriptorSet(b *Backend, cmdBuf vk.CommandBuffer, bindPoint vk.PipelineBindPoint, texBinds [texUnits]*Texture, bufBinds [storageUnits]*Buffer) {
-	realloced := false
-	destroyPool := func() {
+	if p.size == len(p.sets) {
+		l := p.descLayout
+		if l == 0 {
+			panic("vulkan: descriptor set is dirty, but pipeline has empty layout")
+		}
+		newCap := len(p.sets) * 2
 		if pool := p.pool; pool != 0 {
 			b.deferFunc(func(d vk.Device) {
 				vk.DestroyDescriptorPool(d, pool)
 			})
 		}
-		p.pool = 0
-		p.cap = 0
-	}
-	for {
-		if p.size == p.cap {
-			if realloced {
-				panic("vulkan: vkAllocateDescriptorSet failed on a newly allocated descriptor pool")
-			}
-			newCap := p.cap * 2
-			destroyPool()
-			realloced = true
 		const initialPoolSize = 100
 		if newCap < initialPoolSize {
 			newCap = initialPoolSize
@@ -720,21 +712,17 @@ func (p *descPool) bindDescriptorSet(b *Backend, cmdBuf vk.CommandBuffer, bindPo
 		}
 		pool, err := vk.CreateDescriptorPool(b.dev, newCap, poolSizes)
 		if err != nil {
-				panic(fmt.Errorf("vulkan: failed to allocate descriptor pool with %d descriptors", newCap))
+			panic(fmt.Errorf("vulkan: failed to allocate descriptor pool with %d descriptors: %v", newCap, err))
 		}
 		p.pool = pool
-			p.cap = newCap
+		sets, err := vk.AllocateDescriptorSets(b.dev, p.pool, l, newCap)
+		if err != nil {
+			panic(fmt.Errorf("vulkan: failed to allocate descriptor with %d sets: %v", newCap, err))
+		}
+		p.sets = sets
 		p.size = 0
 	}
-		l := p.descLayout
-		if l == 0 {
-			panic("vulkan: descriptor set is dirty, but pipeline has empty layout")
-		}
-		descSet, err := vk.AllocateDescriptorSet(b.dev, p.pool, l)
-		if err != nil {
-			destroyPool()
-			continue
-		}
+	descSet := p.sets[p.size]
 	p.size++
 	for _, bind := range p.texBinds {
 		tex := texBinds[bind]
@@ -752,8 +740,6 @@ func (p *descPool) bindDescriptorSet(b *Backend, cmdBuf vk.CommandBuffer, bindPo
 		vk.UpdateDescriptorSet(b.dev, write)
 	}
 	vk.CmdBindDescriptorSets(cmdBuf, bindPoint, p.layout, 0, []vk.DescriptorSet{descSet})
-		break
-	}
 }
 
 func (t *Texture) imageBarrier(cmdBuf vk.CommandBuffer, layout vk.ImageLayout, stage vk.PipelineStageFlags, access vk.AccessFlags) {

internal/vk/vulkan.go

@@ -1739,18 +1739,22 @@ func UpdateDescriptorSet(d Device, write WriteDescriptorSet) {
 	C.vkUpdateDescriptorSets(funcs.vkUpdateDescriptorSets, d, write, 0, nil)
 }
 
-func AllocateDescriptorSet(d Device, pool DescriptorPool, layout DescriptorSetLayout) (DescriptorSet, error) {
+func AllocateDescriptorSets(d Device, pool DescriptorPool, layout DescriptorSetLayout, count int) ([]DescriptorSet, error) {
+	layouts := make([]DescriptorSetLayout, count)
+	for i := range layouts {
+		layouts[i] = layout
+	}
 	inf := C.VkDescriptorSetAllocateInfo{
 		sType:              C.VK_STRUCTURE_TYPE_DESCRIPTOR_SET_ALLOCATE_INFO,
 		descriptorPool:     pool,
-		descriptorSetCount: 1,
-		pSetLayouts:        &layout,
+		descriptorSetCount: C.uint32_t(count),
+		pSetLayouts:        &layouts[0],
 	}
-	var set C.VkDescriptorSet
-	if err := vkErr(C.vkAllocateDescriptorSets(funcs.vkAllocateDescriptorSets, d, inf, &set)); err != nil {
-		return nilDescriptorSet, fmt.Errorf("vulkan: vkAllocateDescriptorSets: %w", err)
+	sets := make([]DescriptorSet, count, count)
+	if err := vkErr(C.vkAllocateDescriptorSets(funcs.vkAllocateDescriptorSets, d, inf, &sets[0])); err != nil {
+		return nil, fmt.Errorf("vulkan: vkAllocateDescriptorSets: %w", err)
 	}
-	return set, nil
+	return sets, nil
 }
 
 func CreateComputePipeline(d Device, mod ShaderModule, layout PipelineLayout) (Pipeline, error) {