Use memory-mapped I/O on Windows for better random access performance

autonomys · Oct 5, 2023 · 7294cb5 · 7294cb5
1 parent 9679c3d
commit 7294cb5
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diff --git a/Cargo.lock b/Cargo.lock
diff --git a/crates/subspace-farmer/Cargo.toml b/crates/subspace-farmer/Cargo.toml
@@ -59,3 +59,6 @@ zeroize = "1.6.0"
 # The only triple tested and confirmed as working in `jemallocator` crate is `x86_64-unknown-linux-gnu`
 [target.'cfg(all(target_arch = "x86_64", target_vendor = "unknown", target_os = "linux", target_env = "gnu"))'.dependencies]
 jemallocator = "0.5.0"
+
+[target.'cfg(windows)'.dependencies]
+memmap2 = "0.9.0"
diff --git a/crates/subspace-farmer/src/single_disk_farm/farming.rs b/crates/subspace-farmer/src/single_disk_farm/farming.rs
@@ -3,6 +3,8 @@ use crate::node_client::NodeClient;
 use crate::single_disk_farm::Handlers;
 use futures::channel::mpsc;
 use futures::StreamExt;
+#[cfg(windows)]
+use memmap2::{Mmap, MmapOptions};
 use parking_lot::{Mutex, RwLock};
 use rayon::prelude::*;
 use rayon::{ThreadPoolBuildError, ThreadPoolBuilder};
@@ -27,6 +29,16 @@ use tracing::{debug, error, trace, warn};
 /// many solutions.
 const SOLUTIONS_LIMIT: usize = 1;
 
+#[cfg(windows)]
+struct MmapWrapper(Mmap);
+
+#[cfg(windows)]
+impl ReadAt for MmapWrapper {
+    fn read_at(&self, buf: &mut [u8], offset: usize) -> io::Result<()> {
+        self.0.read_at(buf, offset)
+    }
+}
+
 /// Errors that happen during farming
 #[derive(Debug, Error)]
 pub enum FarmingError {
@@ -136,7 +148,27 @@ where
                 .into_par_iter()
                 .zip(&*sectors_metadata)
                 .filter_map(|(sector_index, sector_metadata)| {
+                    #[cfg(not(windows))]
                     let sector = plot_file.offset(sector_index * sector_size);
+                    // On Windows random read is horrible in terms of performance, memory-mapped I/O
+                    // helps
+                    // TODO: Remove this once https://internals.rust-lang.org/t/introduce-write-all-at-read-exact-at-on-windows/19649
+                    //  or similar exists in standard library
+                    #[cfg(windows)]
+                    let maybe_sector = unsafe {
+                        MmapOptions::new()
+                            .offset(sector_index as u64 * sector_size as u64)
+                            .len(sector_size)
+                            .map(plot_file)
+                    };
+                    #[cfg(windows)]
+                    let sector = match maybe_sector {
+                        Ok(sector) => MmapWrapper(sector),
+                        Err(error) => {
+                            warn!(%error, %sector_index, "Failed to memory-map sector");
+                            return None;
+                        }
+                    };
 
                     let sector_index = sector_index as u16;
                     if maybe_sector_being_modified == Some(sector_index) {