3182da3965
Claude Code keeps per-project memory at <home>/.claude/projects/<key>/,
where <key> is the project's absolute path with every separator and the
drive colon turned into a dash. That makes it both rename-fragile and
machine-specific, and this project has hit each of those once:
- D:\DEV\Schunix -> D:\DEV\SchOS changed the key, and 43 memories were
invisible until moved across by hand.
- Development happens from Windows and from Linux, and each looks in a
different place for the same checkout.
Committing .claude/memory/ fixes both -- git carries it across renames
and between hosts -- and `import` puts it wherever the local machine
expects. .claude/settings.local.json stays ignored: those are per-machine
permissions.
The colon maps to a dash rather than being dropped. Deleting it gives
D-DEV-SchOS, which matches nothing and silently finds zero memories; that
was the first attempt. On Git Bash the key comes from `cygpath -w`,
because Claude Code is a Windows program and sees D:\DEV\SchOS, not
/d/DEV/SchOS.
50 lines
2.6 KiB
Markdown
50 lines
2.6 KiB
Markdown
---
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name: schunix-build-speed
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description: The build is fast now (no-op ~2s); the four things that made it slow and the traps that will make it slow again
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metadata:
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node_type: memory
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type: project
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originSessionId: a665e14b-86bd-4b41-a228-51377f3e9225
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modified: 2026-08-04T17:27:56.099Z
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---
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**A no-op `make` went from 1m48s to ~2s on 2026-08-04**, and a full kernel
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rebuild from ~110s to ~7s. Almost none of it was compilation — with only 2.4s
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of CPU in that 1m48, it was I/O across WSL's `/mnt/d` boundary. Four causes,
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all still worth not reintroducing:
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- **`tools/mkfs` built the image on the file**, one `lseek` + one 512-byte
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`write` per block: 300,000 syscall pairs, 150,000 of them just to zero it.
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It now assembles the image in RAM and writes once. It also stops at the last
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non-zero block and `ftruncate`s, so ~2 MB is written instead of 147 MB.
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- **The image was rebuilt on every invocation.** `sysroot-install` is phony, so
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everything depending on it always ran. There is now a `build/sysroot.stamp`
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whose mtime only advances when a `find`-based summary of the staged tree
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actually changes (the `cmp -s ... || mv` idiom — **do not add a `touch`, and
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note `touch -c` still updates an existing file's mtime**, which is exactly
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the bug I wrote and had to remove).
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- **`ports/toybox` re-linked its 236 applets every build**, because port.mk
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declares `install` .PHONY for every port. It hangs off
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`$(BUILDDIR)/toybox.installed` now. This was the sneaky one: it bumped the
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mtime of 236 files in `sysroot/` and so invalidated the stamp above.
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- **mkfs and mkschfs re-read every file to dedup it.** They now check
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`(st_dev, st_ino)` first — toybox's applets are real hard links, so 236 of
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them are settled by one `fstat` instead of ~500 MB of reads.
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Two real bugs found in the Makefile while doing this:
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- **`$(BUILD)/kernel/**/*.d` only matched one directory level.** make's wildcard
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has no recursive `**`. `arch/x86_64/` and `fs/schfs/` therefore had **no
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header dependency tracking at all** — editing `include/schfs.h` left stale
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objects that linked fine. It uses `$(shell find ...)` now.
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- **`CFLAGS` is recursively expanded and had a `$(shell)` appended**, so the
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stack-protector probe re-ran on every expansion: one extra gcc per object
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file. Probed once into `NO_SSP :=` now.
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`schunix.img` is no longer `.PHONY` (it is a real file), and `MAKEFLAGS +=
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-j$(nproc)` is on by default — use `make -j1` for readable output from a
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failing build.
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Verify with `make schfs-check` plus [[schunix-verify-by-driving-shell]]; the
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superblock checksum is printed by mkfs and should not change when only build
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mechanics change.
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