Merge #2264

2264: Render pass descriptor cache for Metal r=grovesNL a=kvark

~~Includes #2260~~
Fixes two of the performance issues in  #2161 (RP desc locking and copying costs).

Immediate recording FPS doesn't seem to change, maybe slightly lower (touching 90 from below more than from above, as I recall it doing - need to confirm. Edit - confirmed to not be caused by the PR).
Deferred recording FPS seem to go from lower 100s to higher, or even from 100 to 110, roughly speaking. There are barely any bottlenecks left for it, outside of the general architecture. Main thread now spends about 14.5% in our code, which is mostly covered by driver interaction.

PR checklist:
- [ ] `make` succeeds (on *nix)
- [x] `make reftests` succeeds
- [x] tested examples with the following backends: Metal
- [ ] `rustfmt` run on changed code


Co-authored-by: Dzmitry Malyshau <kvarkus@gmail.com>

Author: bors[bot]

src/backend/metal/Cargo.toml

@@ -34,4 +34,4 @@ dispatch = "0.1"
 smallvec = "0.6"
 spirv_cross = "0.9"
 parking_lot = "0.6.3"
-storage-map = "0.1"
+storage-map = "0.1.1"

src/backend/metal/src/command.rs

@@ -989,13 +989,7 @@ impl CommandSink {
                 }
             }
             CommandSink::Deferred { ref mut is_encoding, ref mut journal } => {
-                //Note: the original descriptor belongs to the framebuffer,
-                // and will me mutated afterwards.
-                let pass = soft::Pass::Render( unsafe {
-                    let desc: metal::RenderPassDescriptor = msg_send![descriptor, copy];
-                    msg_send![desc.as_ptr(), retain];
-                    desc
-                });
+                let pass = soft::Pass::Render(descriptor.to_owned());
                 let mut range = journal.render_commands.len() .. 0;
                 journal.render_commands.extend(init_commands.map(soft::RenderCommand::own));
                 match door {
@@ -1005,14 +999,9 @@ impl CommandSink {
                 journal.passes.push((pass, range))
             }
             CommandSink::Remote { ref queue, ref cmd_buffer, ref mut pass, ref capacity, .. } => {
-                let desc = unsafe {
-                    let desc: metal::RenderPassDescriptor = msg_send![descriptor, copy];
-                    msg_send![desc.as_ptr(), retain];
-                    desc
-                };
                 let mut list = Vec::with_capacity(capacity.render);
                 list.extend(init_commands.map(soft::RenderCommand::own));
-                let new_pass = EncodePass::Render(list, desc);
+                let new_pass = EncodePass::Render(list, descriptor.to_owned());
                 match door {
                     PassDoor::Open => *pass = Some(new_pass),
                     PassDoor::Closed { .. } => new_pass.schedule(queue, cmd_buffer),
@@ -2696,61 +2685,8 @@ impl com::RawCommandBuffer<Backend> for CommandBuffer {
         T::Item: Borrow<com::ClearValueRaw>,
     {
         // FIXME: subpasses
-        let _ap = AutoreleasePool::new();
-
-        // We are going to modify the RP descriptor here, so
-        // locking to avoid data races.
-        //TODO: if we know that we aren't in the `Immediate` recording mode,
-        // we can copy here right away and void the lock entirely.
-        let descriptor = framebuffer.descriptor.lock();
-
-        let mut num_colors = 0;
-        let mut full_aspects = Aspects::empty();
-        let mut inner = self.inner.borrow_mut();
-
-        let dummy_value = com::ClearValueRaw {
-            color: com:: ClearColorRaw {
-                int32: [0; 4],
-            },
-        };
-        let clear_values_iter = clear_values
-            .into_iter()
-            .map(|c| *c.borrow())
-            .chain(iter::repeat(dummy_value));
-
-        for (rat, clear_value) in render_pass.attachments.iter().zip(clear_values_iter) {
-            let (aspects, channel) = match rat.format {
-                Some(format) => (format.surface_desc().aspects, Channel::from(format.base_format().1)),
-                None => continue,
-            };
-            full_aspects |= aspects;
-            if aspects.contains(Aspects::COLOR) {
-                let color_desc = descriptor
-                    .color_attachments()
-                    .object_at(num_colors)
-                    .unwrap();
-                if set_operations(color_desc, rat.ops) == AttachmentLoadOp::Clear {
-                    let mtl_color = channel
-                        .interpret(unsafe { clear_value.color });
-                    color_desc.set_clear_color(mtl_color);
-                }
-                num_colors += 1;
-            }
-            if aspects.contains(Aspects::DEPTH) {
-                let depth_desc = descriptor.depth_attachment().unwrap();
-                if set_operations(depth_desc, rat.ops) == AttachmentLoadOp::Clear {
-                    let mtl_depth = unsafe { clear_value.depth_stencil.depth as f64 };
-                    depth_desc.set_clear_depth(mtl_depth);
-                }
-            }
-            if aspects.contains(Aspects::STENCIL) {
-                let stencil_desc = descriptor.stencil_attachment().unwrap();
-                if set_operations(stencil_desc, rat.stencil_ops) == AttachmentLoadOp::Clear {
-                    let mtl_stencil = unsafe { clear_value.depth_stencil.stencil };
-                    stencil_desc.set_clear_stencil(mtl_stencil);
-                }
-            }
-        }
+        let desc_guard;
+        let (rp_key, full_aspects) = render_pass.build_key(clear_values);
 
         self.state.render_pso_is_compatible = match self.state.render_pso {
             Some(ref ps) => ps.at_formats.len() == render_pass.attachments.len() &&
@@ -2759,6 +2695,7 @@ impl com::RawCommandBuffer<Backend> for CommandBuffer {
         };
 
         self.state.framebuffer_inner = framebuffer.inner.clone();
+
         let ds_store = &self.shared.service_pipes.depth_stencil_states;
         let ds_state;
         let com_ds = if full_aspects.intersects(Aspects::DEPTH | Aspects::STENCIL) {
@@ -2776,9 +2713,62 @@ impl com::RawCommandBuffer<Backend> for CommandBuffer {
             .make_render_commands(full_aspects)
             .chain(com_ds);
 
-        inner
+        desc_guard = framebuffer.desc_storage
+            .get_or_create_with(&rp_key, || {
+                let _ap = AutoreleasePool::new();
+                let mut clear_id = 0;
+                let mut num_colors = 0;
+                let rp_desc = unsafe {
+                    let desc: metal::RenderPassDescriptor = msg_send![framebuffer.descriptor, copy];
+                    msg_send![desc.as_ptr(), retain];
+                    desc
+                };
+
+                for rat in &render_pass.attachments {
+                    let (aspects, channel) = match rat.format {
+                        Some(format) => (format.surface_desc().aspects, Channel::from(format.base_format().1)),
+                        None => continue,
+                    };
+                    if aspects.contains(Aspects::COLOR) {
+                        let color_desc = rp_desc
+                            .color_attachments()
+                            .object_at(num_colors)
+                            .unwrap();
+                        if set_operations(color_desc, rat.ops) == AttachmentLoadOp::Clear {
+                            let d = &rp_key.clear_data[clear_id .. clear_id + 4];
+                            clear_id += 4;
+                            let raw = com::ClearColorRaw {
+                                uint32: [d[0], d[1], d[2], d[3]],
+                            };
+                            color_desc.set_clear_color(channel.interpret(raw));
+                        }
+                        num_colors += 1;
+                    }
+                    if aspects.contains(Aspects::DEPTH) {
+                        let depth_desc = rp_desc.depth_attachment().unwrap();
+                        if set_operations(depth_desc, rat.ops) == AttachmentLoadOp::Clear {
+                            let raw = unsafe { *(&rp_key.clear_data[clear_id] as *const _ as *const f32) };
+                            clear_id += 1;
+                            depth_desc.set_clear_depth(raw as f64);
+                        }
+                    }
+                    if aspects.contains(Aspects::STENCIL) {
+                        let stencil_desc = rp_desc.stencil_attachment().unwrap();
+                        if set_operations(stencil_desc, rat.stencil_ops) == AttachmentLoadOp::Clear {
+                            let raw = rp_key.clear_data[clear_id];
+                            clear_id += 1;
+                            stencil_desc.set_clear_stencil(raw);
+                        }
+                    }
+                }
+
+                rp_desc
+            });
+
+        self.inner
+            .borrow_mut()
             .sink()
-            .begin_render_pass(PassDoor::Open, &*descriptor, init_commands);
+            .begin_render_pass(PassDoor::Open, &**desc_guard, init_commands);
     }
 
     fn next_subpass(&mut self, _contents: com::SubpassContents) {
@@ -2821,38 +2811,39 @@ impl com::RawCommandBuffer<Backend> for CommandBuffer {
         let mut pre = inner.sink().pre_render();
 
         self.state.render_pso_is_compatible = true; //assume good intent :)
-        let mut set_pipeline = false;
-        match self.state.render_pso {
+        let set_pipeline = match self.state.render_pso {
+            Some(ref ps) if ps.raw.as_ptr() == pipeline.raw.as_ptr() => {
+                false // chill out
+            }
             Some(ref mut ps) => {
-                // try to avoid extra states or new heap allocations
-                if ps.raw.as_ptr() != pipeline.raw.as_ptr() {
-                    ps.raw = pipeline.raw.to_owned();
-                    set_pipeline = true;
-                }
-                ps.ds_desc = pipeline.depth_stencil_desc.clone();
+                ps.raw = pipeline.raw.to_owned();
                 ps.vbuf_map.clear();
                 ps.vbuf_map.extend(&pipeline.vertex_buffer_map);
+                ps.ds_desc = pipeline.depth_stencil_desc.clone();
                 ps.at_formats.clear();
                 ps.at_formats.extend_from_slice(&pipeline.attachment_formats);
+                true
             }
             None => {
-                set_pipeline = true;
                 self.state.render_pso = Some(RenderPipelineState {
                     raw: pipeline.raw.to_owned(),
                     ds_desc: pipeline.depth_stencil_desc.clone(),
                     vbuf_map: pipeline.vertex_buffer_map.clone(),
                     at_formats: pipeline.attachment_formats.clone(),
                 });
+                true
             }
-        }
+        };
         if set_pipeline {
             pre.issue(soft::RenderCommand::BindPipeline(&*pipeline.raw));
-        }
-
-        self.state.rasterizer_state = pipeline.rasterizer_state.clone();
-        self.state.primitive_type = pipeline.primitive_type;
-        if let Some(ref rs) = pipeline.rasterizer_state {
-            pre.issue(soft::RenderCommand::SetRasterizerState(rs.clone()))
+            self.state.rasterizer_state = pipeline.rasterizer_state.clone();
+            self.state.primitive_type = pipeline.primitive_type;
+            if let Some(ref rs) = pipeline.rasterizer_state {
+                pre.issue(soft::RenderCommand::SetRasterizerState(rs.clone()))
+            }
+        } else {
+            debug_assert_eq!(self.state.rasterizer_state, pipeline.rasterizer_state);
+            debug_assert_eq!(self.state.primitive_type, pipeline.primitive_type);
         }
 
         if let Some(desc) = self.state.build_depth_stencil() {

src/backend/metal/src/device.rs

@@ -3,6 +3,7 @@ use {
     Shared, Surface, Swapchain, validate_line_width, BufferPtr, SamplerPtr, TexturePtr,
 };
 use {conversions as conv, command, native as n};
+use internal::FastStorageMap;
 use native;
 use range_alloc::RangeAllocator;
 
@@ -1095,7 +1096,8 @@ impl hal::Device<Backend> for Device {
         }
 
         Ok(n::Framebuffer {
-            descriptor: Mutex::new(descriptor),
+            descriptor,
+            desc_storage: FastStorageMap::default(),
             inner,
         })
     }

src/backend/metal/src/native.rs

@@ -1,17 +1,20 @@
 use {Backend, BufferPtr, SamplerPtr, TexturePtr};
-use internal::Channel;
+use internal::{Channel, FastStorageMap};
 use range_alloc::RangeAllocator;
 use window::SwapchainImage;
 
+use std::borrow::Borrow;
 use std::cell::RefCell;
-use std::fmt;
+use std::{fmt, iter};
 use std::ops::Range;
 use std::os::raw::{c_void, c_long};
 use std::sync::Arc;
 
 use hal::{self, image, pso};
 use hal::backend::FastHashMap;
+use hal::command::{ClearColorRaw, ClearValueRaw};
 use hal::format::{Aspects, Format, FormatDesc};
+use hal::pass::{Attachment, AttachmentLoadOp, AttachmentOps};
 
 use cocoa::foundation::{NSUInteger};
 use foreign_types::ForeignType;
@@ -49,14 +52,73 @@ impl fmt::Debug for ShaderModule {
 unsafe impl Send for ShaderModule {}
 unsafe impl Sync for ShaderModule {}
 
+#[derive(Clone, Debug, Default, Hash, PartialEq, Eq)]
+pub struct RenderPassKey {
+    // enough room for 4 color targets + depth/stencil
+    operations: SmallVec<[AttachmentOps; 5]>,
+    pub clear_data: SmallVec<[u32; 10]>,
+}
+
 #[derive(Debug)]
 pub struct RenderPass {
-    pub(crate) attachments: Vec<hal::pass::Attachment>,
+    pub(crate) attachments: Vec<Attachment>,
 }
 
 unsafe impl Send for RenderPass {}
 unsafe impl Sync for RenderPass {}
 
+impl RenderPass {
+    pub fn build_key<T>(&self, clear_values: T) -> (RenderPassKey, Aspects)
+    where
+        T: IntoIterator,
+        T::Item: Borrow<ClearValueRaw>,
+    {
+        let mut key = RenderPassKey::default();
+        let mut full_aspects = Aspects::empty();
+
+        let dummy_value = ClearValueRaw {
+            color: ClearColorRaw {
+                int32: [0; 4],
+            },
+        };
+        let clear_values_iter = clear_values
+            .into_iter()
+            .map(|c| *c.borrow())
+            .chain(iter::repeat(dummy_value));
+
+        for (rat, clear_value) in self.attachments.iter().zip(clear_values_iter) {
+            //TODO: avoid calling `surface_desc` as often
+            let aspects = match rat.format {
+                Some(format) => format.surface_desc().aspects,
+                None => continue,
+            };
+            full_aspects |= aspects;
+            let cv = clear_value.borrow();
+
+            if aspects.contains(Aspects::COLOR) {
+                key.operations.push(rat.ops);
+                if rat.ops.load == AttachmentLoadOp::Clear {
+                    key.clear_data.extend_from_slice(unsafe { &cv.color.uint32 });
+                }
+            }
+            if aspects.contains(Aspects::DEPTH) {
+                key.operations.push(rat.ops);
+                if rat.ops.load == AttachmentLoadOp::Clear {
+                    key.clear_data.push(unsafe { *(&cv.depth_stencil.depth as *const _ as *const u32) });
+                }
+            }
+            if aspects.contains(Aspects::STENCIL) {
+                key.operations.push(rat.stencil_ops);
+                if rat.stencil_ops.load == AttachmentLoadOp::Clear {
+                    key.clear_data.push(unsafe { cv.depth_stencil.stencil });
+                }
+            }
+        }
+
+        (key, full_aspects)
+    }
+}
+
 #[derive(Clone, Debug)]
 pub struct ColorAttachment {
     pub mtl_format: metal::MTLPixelFormat,
@@ -73,7 +135,8 @@ pub struct FramebufferInner {
 
 #[derive(Debug)]
 pub struct Framebuffer {
-    pub(crate) descriptor: Mutex<metal::RenderPassDescriptor>,
+    pub(crate) descriptor: metal::RenderPassDescriptor,
+    pub(crate) desc_storage: FastStorageMap<RenderPassKey, metal::RenderPassDescriptor>,
     pub(crate) inner: FramebufferInner,
 }
 
@@ -115,7 +178,7 @@ impl PipelineLayout {
     }
 }
 
-#[derive(Clone, Debug)]
+#[derive(Clone, Debug, PartialEq)]
 pub struct RasterizerState {
     //TODO: more states
     pub front_winding: metal::MTLWinding,