From 68195321c58e20a27c8ee7813804c1ae28f9795b Mon Sep 17 00:00:00 2001 From: Nazar Mokrynskyi Date: Sun, 10 Mar 2024 03:45:37 +0200 Subject: [PATCH] Leverage emulated sector size on Windows to decrease usage of the interface bandwidth with SSD --- .../unbuffered_io_file_windows.rs | 69 +++++++++++++------ 1 file changed, 49 insertions(+), 20 deletions(-) diff --git a/crates/subspace-farmer/src/single_disk_farm/unbuffered_io_file_windows.rs b/crates/subspace-farmer/src/single_disk_farm/unbuffered_io_file_windows.rs index 67e4361908..8691244fd1 100644 --- a/crates/subspace-farmer/src/single_disk_farm/unbuffered_io_file_windows.rs +++ b/crates/subspace-farmer/src/single_disk_farm/unbuffered_io_file_windows.rs @@ -16,6 +16,7 @@ const MAX_READ_SIZE: usize = 1024 * 1024; pub struct UnbufferedIoFileWindows { read_file: File, write_file: File, + physical_sector_size: usize, /// Scratch buffer of aligned memory for reads and writes buffer: Mutex>, } @@ -66,9 +67,14 @@ impl FileExt for UnbufferedIoFileWindows { buffer.resize(desired_buffer_size, [0; DISK_SECTOR_SIZE]); } + // While buffer above is allocated with granularity of `MAX_DISK_SECTOR_SIZE`, reads are + // done with granularity of physical sector size + let offset_in_buffer = (offset % self.physical_sector_size as u64) as usize; self.read_file.read_at( - buffer[..desired_buffer_size].flatten_mut(), - offset / DISK_SECTOR_SIZE as u64 * DISK_SECTOR_SIZE as u64, + &mut buffer.flatten_mut()[..(bytes_to_read + offset_in_buffer) + .div_ceil(self.physical_sector_size) + * self.physical_sector_size], + offset / self.physical_sector_size as u64 * self.physical_sector_size as u64, )?; buf.copy_from_slice(&buffer.flatten()[offset_in_buffer..][..bytes_to_read]); @@ -103,9 +109,17 @@ impl UnbufferedIoFileWindows { open_options.advise_unbuffered(); let read_file = open_options.read(true).open(path)?; + // Physical sector size on many SSDs is smaller than 4096 and should improve performance + let physical_sector_size = if read_file.read_at(&mut [0; 512], 512).is_ok() { + 512 + } else { + DISK_SECTOR_SIZE + }; + Ok(Self { read_file, write_file, + physical_sector_size, buffer: Mutex::default(), }) } @@ -134,24 +148,39 @@ mod tests { thread_rng().fill(data.as_mut_slice()); fs::write(&file_path, &data).unwrap(); - let file = UnbufferedIoFileWindows::open(&file_path).unwrap(); - - let mut buffer = Vec::new(); - for (offset, size) in [ - (0_usize, 4096_usize), - (0, 4000), - (5, 50), - (5, 4091), - (5, MAX_READ_SIZE * 2), - ] { - buffer.resize(size, 0); - file.read_at(buffer.as_mut_slice(), offset as u64) - .unwrap_or_else(|error| panic!("Offset {offset}, size {size}: {error}")); - assert_eq!( - &data[offset..][..size], - buffer.as_slice(), - "Offset {offset}, size {size}" - ); + let mut file = UnbufferedIoFileWindows::open(&file_path).unwrap(); + + for override_physical_sector_size in [None, Some(4096)] { + if let Some(physical_sector_size) = override_physical_sector_size { + file.physical_sector_size = physical_sector_size; + } + + let mut buffer = Vec::new(); + for (offset, size) in [ + (0_usize, 4096_usize), + (0, 4000), + (5, 50), + (5, 4091), + (4091, 5), + (10000, 5), + (5, MAX_READ_SIZE * 2), + ] { + buffer.resize(size, 0); + file.read_at(buffer.as_mut_slice(), offset as u64) + .unwrap_or_else(|error| { + panic!( + "Offset {offset}, size {size}, override physical sector size \ + {override_physical_sector_size:?}: {error}" + ) + }); + + assert_eq!( + &data[offset..][..size], + buffer.as_slice(), + "Offset {offset}, size {size}, override physical sector size \ + {override_physical_sector_size:?}" + ); + } } } }