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iter10: chunk back to 32 MiB

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iter9 (64 MiB on top of no-P2.5) regressed -1.2 from iter8. 32 MiB
remains best on the no-P2.5 path. Net iter10 = iter8 minus DONTNEED
(via the prior commit re-applying f4a881b).
This commit is contained in:
MattJackson
2026-05-17 09:06:34 -07:00
parent f7165a2020
commit 31dc3d35c3
1 changed files with 2 additions and 8 deletions
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src/io/writeback_file/mod.rs
+2 -8
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@@ -73,14 +73,8 @@ use std::path::Path;
use super::writeback::WritebackPipeline; use super::writeback::WritebackPipeline;
/// Granularity at which the Linux writeback pipeline issues /// Granularity at which the Linux writeback pipeline issues
/// `sync_file_range` / `posix_fadvise(DONTNEED)` pairs. /// `sync_file_range` pairs. 32 MiB best-tested with iter8 (28.7 mean).
/// const WRITEBACK_CHUNK_BYTES: u64 = 32 * 1024 * 1024;
/// iter9 (2026-05-17): 32 → 64 MiB on top of iter8 (Phase 2.5
/// disabled). Without Phase 2.5's writer thread, WAIT_AFTER blocks
/// the mux thread directly. Bigger chunks = fewer WAIT_AFTER calls
/// = less mux-thread blocking. iter8 mean was 28.7 with 32 MiB; aim
/// to clear the 30 floor by halving WAIT_AFTER frequency.
const WRITEBACK_CHUNK_BYTES: u64 = 64 * 1024 * 1024;
pub(crate) struct WritebackFile { pub(crate) struct WritebackFile {
file: File, file: File,