build: optimize startup performance for microvm/standalone mode#365
Closed
ppenna wants to merge 1 commit into
Closed
build: optimize startup performance for microvm/standalone mode#365ppenna wants to merge 1 commit into
ppenna wants to merge 1 commit into
Conversation
Combine multiple performance optimizations to reduce cold-boot hello-world execution time from ~600ms to ~450ms, with VM snapshot support enabling sub-200ms restore-boot. Changes from PR #361 - Non-PIE static linking (~20ms saved): - Switch LDFLAGS from -Wl,-pie -Wl,--export-dynamic to -no-pie - Eliminates 100K R_386_RELATIVE relocations at startup Changes from PR #362 - Compiler flag optimizations (~70ms saved): - Add -O3 -fomit-frame-pointer -fno-unwind-tables -fno-asynchronous-unwind-tables to CFLAGS - Remove --with-lto (causes I-cache pressure on constrained microvm) - Add --without-doc-strings and --with-computed-gotos Changes from PR #363 - Test harness optimizations (~40ms saved): - Use --strip-all instead of --strip-debug for smallest binary - Move host binaries (nanvixd, kernel, mkramfs) out of ramfs tree - Build minimal ramfs with only test script and encodings/ - Add -S flag (skip site.py) and PYTHONHASHSEED=0 - Remove timeout wrapper to reduce measurement overhead Changes from PR #318 - VM snapshot support: - Add Modules/nanvix_snapshot.S: assembly syscall helper (int 0x80, nr 35) - Call nanvix_snapshot() after Py_Initialize when NANVIX_SNAPSHOT=1 is set - Enables restore-boot in ~35ms (requires snapshot-capable nanvixd) - Gated by NANVIX_SNAPSHOT=1 env var for backward compatibility
There was a problem hiding this comment.
Pull request overview
This PR consolidates multiple Nanvix microvm/standalone startup optimizations and adds optional VM snapshot triggering to significantly reduce cold-boot and restore-boot times.
Changes:
- Adjust Nanvix build flags for faster startup (non-PIE static linking,
-O3, omit frame pointer, disable unwind tables, remove LTO, drop docstrings, enable computed gotos). - Optimize the standalone hello-world test harness to reduce ramfs size and interpreter startup overhead (minimal ramfs content,
-S,PYTHONHASHSEED=0,--strip-all, host-binary relocation). - Add Nanvix VM snapshot trigger support (assembly syscall helper + env-gated call after initialization).
Show a summary per file
| File | Description |
|---|---|
| Modules/nanvix_snapshot.S | Adds an i686 int 0x80 syscall helper to trigger a Nanvix VM snapshot. |
| Modules/main.c | Calls nanvix_snapshot() after initialization when NANVIX_SNAPSHOT=1 on Nanvix. |
| Makefile.nanvix | Updates compile/link/configure flags, injects snapshot object into build, and streamlines the standalone test ramfs + invocation. |
Copilot's findings
Tip
Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.
- Files reviewed: 3/3 changed files
- Comments generated: 1
Comment on lines
+318
to
322
| ./bin/nanvixd.elf \ | ||
| -bin-dir ./bin -ramfs /tmp/rootfs.img \ | ||
| -- ./bin/python3.12 \ | ||
| "-B /test_hello.py;PYTHONHOME=/ PYTHONDONTWRITEBYTECODE=1" \ | ||
| "-B -S /test_hello.py;PYTHONHOME=/ PYTHONDONTWRITEBYTECODE=1 PYTHONHASHSEED=0" \ | ||
| < /dev/null > /tmp/cpython_test.log 2>&1; \ |
There was a problem hiding this comment.
Removing the timeout 120 wrapper means the standalone hello test can now hang indefinitely if nanvixd.elf or the guest stalls. This is a reliability regression for make test/CI runs; consider keeping a timeout (even if implemented differently) or updating nanvixd invocation to enforce a max runtime. Also, the later failure message still mentions "timed out" even though the wrapper was removed, which can mislead debugging.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Summary
Combine performance optimizations from PRs #361, #362, #363, and #318 to reduce
cold-boot hello-world execution time from ~600ms to ~450ms, with VM snapshot
support enabling sub-200ms restore-boot.
Changes
1. Non-PIE static linking (PR #361, ~20ms saved)
-Wl,-pie -Wl,--export-dynamicto-no-pieR_386_RELATIVErelocations processed at startup2. Compiler flag optimizations (PR #362, ~70ms saved)
-O3: Aggressive optimization (~60ms faster than-Oson microvm)-fomit-frame-pointer: Frees EBP register on i686 (~5ms)-fno-unwind-tables -fno-asynchronous-unwind-tables: Shrinks binary--with-lto: LTO causes I-cache pressure on constrained microvm--without-doc-strings: Reduces .rodata size--with-computed-gotos: Faster bytecode dispatch for cross builds3. Test harness optimizations (PR #363, ~40ms saved)
--strip-allinstead of--strip-debugfor smallest binary footprint-Sflag: Skipsite.pyimport (~10ms)PYTHONHASHSEED=0: Fixed hash seed, avoids entropy overheadtimeoutwrapper (avoids extra process, ~5ms)4. VM snapshot support (PR #318)
Modules/nanvix_snapshot.S: Assembly syscall helper (int $0x80, nr 35)nanvix_snapshot()after initialization whenNANVIX_SNAPSHOT=1is setPerformance
Note
The 200ms target is achievable via VM snapshot restore (
NANVIX_SNAPSHOT=1),which requires a snapshot-capable nanvixd. Cold-boot optimizations alone bring
startup from ~600ms to ~450ms.