Expand Miri's BorTag GC to a Provenance GC #118029

saethlin · 2023-11-18T01:40:50Z

As suggested in rust-lang/miri#3080 (comment)

We previously solved memory growth issues associated with the Stacked Borrows and Tree Borrows runtimes with a GC. But of course we also have state accumulation associated with whole allocations elsewhere in the interpreter, and this PR starts tackling those.

To do this, we expand the visitor for the GC so that it can visit a BorTag or an AllocId. Instead of collecting all live AllocIds into a single HashSet, we just collect from the Machine itself then go through an accessor InterpCx::is_alloc_live which checks a number of allocation data structures in the core interpreter. This avoids the overhead of all the inserts that collecting their keys would require.

r? @RalfJung

saethlin · 2023-11-18T02:31:04Z

That was 30 minutes without "Collect Me 🥺" mode, let's see what it is now...

saethlin · 2023-11-18T03:04:19Z

Of course that didn't do anything. Working with the test suite is never that easy.

compiler/rustc_const_eval/src/interpret/machine.rs

RalfJung

Looks good, but I wonder what the effects on performance are.

Also, please add the testcase you posted in the other PR.

compiler/rustc_const_eval/src/interpret/memory.rs

src/ci/docker/host-x86_64/x86_64-gnu-tools/checktools.sh

src/tools/miri/README.md

src/tools/miri/src/intptrcast.rs

RalfJung · 2023-11-18T17:32:39Z

compiler/rustc_const_eval/src/interpret/memory.rs

+ pub fn is_alloc_live(&self, id: AllocId) -> bool {
+ self.tcx.try_get_global_alloc(id).is_some()
+ || self.memory.alloc_map.contains_key_ref(&id)
+ || self.memory.extra_fn_ptr_map.contains_key(&id)


Is it worth thinking about the order in which we check these? get_alloc_info checks memory.alloc_map first sine I assume that's the most common case.

I tuned the order against the test 0weak_memory_consistency, because its runtime explodes after this PR with GC every block. I'll try some other programs.

Looked a bit more into this. I've run (chunks of) the test suites for regex, simd-json, and http and in all these cases > 40% of all the checks for an AllocId result in GlobalAlloc::Memory, but in the 0weak_memory_consistency test, the biggest hit is GlobalAlloc::Function (oddly enough the fraction of hits on functions climbs as the test goes on, not sure why, I'd expect every turn of the loop in that test to be the same).

Since all the global allocs can never be deallocated I think it might be worth stealing a bit from AllocId so that the Id itself can locally indicate whether the allocation deallocated; that would let us skip over them in the GC without consulting a hash table.

So you're saying we should stay with "global first" for now? Works for me.

saethlin · 2023-11-18T18:16:14Z

Looks good, but I wonder what the effects on performance are.

Looks like a 2% improvement, based on bumping up the invalidate benchmark's iterations to 1_000_000 (which only bumps the wall time to 40 seconds, which is long for a benchmark but not for something like a test suite). The fact that this halves the peak memory of that program is more exciting to me.

RalfJung · 2023-11-18T18:20:50Z

Could you run our entire benchmark suite, just to make sure we don't accidentally introduce a big regression somewhere? (I hope the default 10k blocks interval is enough that the GC is triggered a couple times during the benchmark.^^)

saethlin · 2023-11-18T21:07:10Z

Everything is within noise, except for the invalidate benchmark with increased iterations. If there are any changes which could be revealed by bumping up the size of the other, they are marginal.

Commit I branched off:

Benchmark 1: cargo +stage2 miri run --manifest-path=bench-cargo-miri/backtraces/Cargo.toml
  Time (mean ± σ):      4.179 s ±  0.021 s    [User: 4.046 s, System: 0.123 s]
  Range (min … max):    4.151 s …  4.207 s    5 runs
 
Benchmark 1: cargo +stage2 miri run --manifest-path=bench-cargo-miri/invalidate/Cargo.toml
  Time (mean ± σ):     40.131 s ±  0.648 s    [User: 39.924 s, System: 0.153 s]
  Range (min … max):   39.621 s … 41.249 s    5 runs
 
Benchmark 1: cargo +stage2 miri run --manifest-path=bench-cargo-miri/mse/Cargo.toml
  Time (mean ± σ):     746.6 ms ±   7.1 ms    [User: 670.2 ms, System: 71.7 ms]
  Range (min … max):   737.5 ms … 754.6 ms    5 runs
 
Benchmark 1: cargo +stage2 miri run --manifest-path=bench-cargo-miri/serde1/Cargo.toml
  Time (mean ± σ):      2.458 s ±  0.020 s    [User: 2.366 s, System: 0.085 s]
  Range (min … max):    2.440 s …  2.491 s    5 runs
 
Benchmark 1: cargo +stage2 miri run --manifest-path=bench-cargo-miri/serde2/Cargo.toml
  Time (mean ± σ):      5.099 s ±  0.016 s    [User: 4.994 s, System: 0.095 s]
  Range (min … max):    5.079 s …  5.115 s    5 runs
 
Benchmark 1: cargo +stage2 miri run --manifest-path=bench-cargo-miri/slice-get-unchecked/Cargo.toml
  Time (mean ± σ):     666.3 ms ±   4.5 ms    [User: 583.4 ms, System: 79.0 ms]
  Range (min … max):   662.0 ms … 673.2 ms    5 runs
 
Benchmark 1: cargo +stage2 miri run --manifest-path=bench-cargo-miri/unicode/Cargo.toml
  Time (mean ± σ):      1.675 s ±  0.013 s    [User: 1.588 s, System: 0.082 s]
  Range (min … max):    1.661 s …  1.697 s    5 runs
 
Benchmark 1: cargo +stage2 miri run --manifest-path=bench-cargo-miri/zip-equal/Cargo.toml
  Time (mean ± σ):      2.644 s ±  0.042 s    [User: 2.546 s, System: 0.091 s]
  Range (min … max):    2.576 s …  2.690 s    5 runs

This PR:

Benchmark 1: cargo +stage2 miri run --manifest-path=bench-cargo-miri/backtraces/Cargo.toml
  Time (mean ± σ):      4.117 s ±  0.036 s    [User: 4.015 s, System: 0.093 s]
  Range (min … max):    4.078 s …  4.155 s    5 runs
 
Benchmark 1: cargo +stage2 miri run --manifest-path=bench-cargo-miri/invalidate/Cargo.toml
  Time (mean ± σ):     38.479 s ±  0.119 s    [User: 38.337 s, System: 0.091 s]
  Range (min … max):   38.300 s … 38.588 s    5 runs
 
Benchmark 1: cargo +stage2 miri run --manifest-path=bench-cargo-miri/mse/Cargo.toml
  Time (mean ± σ):     743.8 ms ±   5.6 ms    [User: 666.1 ms, System: 73.9 ms]
  Range (min … max):   737.5 ms … 748.9 ms    5 runs
 
Benchmark 1: cargo +stage2 miri run --manifest-path=bench-cargo-miri/serde1/Cargo.toml
  Time (mean ± σ):      2.434 s ±  0.033 s    [User: 2.349 s, System: 0.078 s]
  Range (min … max):    2.403 s …  2.481 s    5 runs
 
Benchmark 1: cargo +stage2 miri run --manifest-path=bench-cargo-miri/serde2/Cargo.toml
  Time (mean ± σ):      5.138 s ±  0.025 s    [User: 4.912 s, System: 0.083 s]
  Range (min … max):    5.105 s …  5.171 s    5 runs
 
Benchmark 1: cargo +stage2 miri run --manifest-path=bench-cargo-miri/slice-get-unchecked/Cargo.toml
  Time (mean ± σ):     671.7 ms ±   7.1 ms    [User: 594.0 ms, System: 72.3 ms]
  Range (min … max):   663.4 ms … 677.6 ms    5 runs
 
Benchmark 1: cargo +stage2 miri run --manifest-path=bench-cargo-miri/unicode/Cargo.toml
  Time (mean ± σ):      1.649 s ±  0.029 s    [User: 1.570 s, System: 0.073 s]
  Range (min … max):    1.603 s …  1.684 s    5 runs
 
Benchmark 1: cargo +stage2 miri run --manifest-path=bench-cargo-miri/zip-equal/Cargo.toml
  Time (mean ± σ):      2.597 s ±  0.040 s    [User: 2.487 s, System: 0.104 s]
  Range (min … max):    2.528 s …  2.632 s    5 runs

saethlin · 2023-11-18T21:13:20Z

The benchmark that runs the GC the least is slice-get-unchecked, which runs it 14 times. I think that's probably good enough.

saethlin · 2023-11-19T00:32:40Z

Running the fail tests too looks like it adds 2 or 3 minutes to the x86_64-gnu-tools CI job. I want to do that because it will make this next thing easier...

saethlin · 2023-11-19T01:49:34Z

Always setting -Zmiri-provenance-gc=1 even if we override it in 0weak_memory_consistency adds ~21 minutes to CI time. That's not great.

saethlin · 2023-11-19T04:03:36Z

~8 minutes total increase in CI time. That seems a bit excessive. Let's try applying the "just run pass tests" trick again?

saethlin · 2023-11-19T05:23:58Z

That shaved off maybe two minutes (uncertain of noise, not going to try checking).

For all the targets without -Zmiri-provenance-gc=1 we spend 33 seconds building the sysroot then 30 seconds running the tests. With -Zmiri-provenance-gc=1 running the tests takes 220 seconds.

In my opinion, for now the best compromise is to just run one target with -Zmiri-provenance-gc=1. I have an idea on how to make the GC faster that I might be able to land in a few days so I'd prefer to get this PR in then work on that and promote more targets to -Zmiri-provenance-gc=1.

rustbot · 2023-11-19T05:28:35Z

Some changes occurred to the CTFE / Miri engine

cc @rust-lang/miri

Some changes occurred to the CTFE / Miri engine

cc @rust-lang/miri

The Miri subtree was changed

cc @rust-lang/miri

saethlin · 2023-11-19T18:34:01Z

@bors r=RalfJung

bors · 2023-11-19T18:34:03Z

📌 Commit d7661d5 has been approved by RalfJung

It is now in the queue for this repository.

bors · 2023-11-20T13:28:58Z

⌛ Testing commit d7661d5 with merge dadde3e...

Expand Miri's BorTag GC to a Provenance GC As suggested in rust-lang/miri#3080 (comment) We previously solved memory growth issues associated with the Stacked Borrows and Tree Borrows runtimes with a GC. But of course we also have state accumulation associated with whole allocations elsewhere in the interpreter, and this PR starts tackling those. To do this, we expand the visitor for the GC so that it can visit a BorTag or an AllocId. Instead of collecting all live AllocIds into a single HashSet, we just collect from the Machine itself then go through an accessor `InterpCx::is_alloc_live` which checks a number of allocation data structures in the core interpreter. This avoids the overhead of all the inserts that collecting their keys would require. r? `@RalfJung`

RalfJung · 2023-11-20T13:58:32Z

src/ci/docker/host-x86_64/x86_64-gnu-tools/checktools.sh

+# We set the GC interval to the shortest possible value (0 would be off) to increase the chance
+# that bugs which only surface when the GC runs at a specific time are more likely to cause CI to fail.
+# This significantly increases the runtime of our test suite, or we'd do this in PR CI too.
+if [[ -z "${PR_CI_JOB}" ]]; then


Ah, with -u set, testing for the existence of a shell variable is not so easy any more... :/

Ah! The place I got this from doesn't use -u so I guess I'll do as that script does

Ah, +u/-u dance seems safer (I really do hate shell scripting)

Ugh no please don't.

[[ -z "${PR_CI_JOB-}" ]] should work, the ${PR_CI_JOB-default}syntax means "fall back todefault` if variable does not exist" and here we use an empty default.

Hm. So we just need to lose -u for the whole script?

Or modify the caller to always set the variable?

No, just use "${PR_CI_JOB-}" instead of "${PR_CI_JOB}"

saethlin · 2023-11-20T14:15:29Z

@bors r=RalfJung

bors · 2023-11-20T14:15:34Z

📌 Commit 5376e72 has been approved by RalfJung

It is now in the queue for this repository.

RalfJung · 2023-11-20T14:18:44Z

@bors r-

RalfJung · 2023-11-20T14:40:51Z

src/ci/docker/host-x86_64/x86_64-gnu-tools/checktools.sh

+# We set the GC interval to the shortest possible value (0 would be off) to increase the chance
+# that bugs which only surface when the GC runs at a specific time are more likely to cause CI to fail.
+# This significantly increases the runtime of our test suite, or we'd do this in PR CI too.
+if [[ -z "${PR_CI_JOB:-}" ]]; then


I had suggested the version without :, but with : also works here.

I tried to look up docs for shell expansion and I could only find the ones with :- documented and that's what the Miri repo uses. What changes if the colon is omitted?

I can't find the page I got this from but https://stackoverflow.com/a/16753536 lists them all. They behave differently when the variable exists but is empty.

https://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html says this before the list that has :- etc

Omitting the colon results in a test only for a parameter that is unset. Put another way, if the colon is included, the operator tests for both parameter’s existence and that its value is not null; if the colon is omitted, the operator tests only for existence.

I'd say the version without the colon is the more reasonable semantics (null != does-not-exist), but the shell world is weird.^^

RalfJung · 2023-11-20T14:41:07Z

@bors r+

bors · 2023-11-20T14:41:11Z

📌 Commit 9ada654 has been approved by RalfJung

It is now in the queue for this repository.

Expand Miri's BorTag GC to a Provenance GC As suggested in rust-lang/miri#3080 (comment) We previously solved memory growth issues associated with the Stacked Borrows and Tree Borrows runtimes with a GC. But of course we also have state accumulation associated with whole allocations elsewhere in the interpreter, and this PR starts tackling those. To do this, we expand the visitor for the GC so that it can visit a BorTag or an AllocId. Instead of collecting all live AllocIds into a single HashSet, we just collect from the Machine itself then go through an accessor `InterpCx::is_alloc_live` which checks a number of allocation data structures in the core interpreter. This avoids the overhead of all the inserts that collecting their keys would require. r? `@RalfJung`

Rollup of 6 pull requests Successful merges: - rust-lang#116085 (rustdoc-search: add support for traits and associated types) - rust-lang#117522 (Remove `--check-cfg` checking of command line `--cfg` args) - rust-lang#118029 (Expand Miri's BorTag GC to a Provenance GC) - rust-lang#118035 (Fix early param lifetimes in generic_const_exprs) - rust-lang#118083 (Remove i686-apple-darwin cross-testing) - rust-lang#118091 (Remove now deprecated target x86_64-sun-solaris.) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of rust-lang#118029 - saethlin:allocid-gc, r=RalfJung Expand Miri's BorTag GC to a Provenance GC As suggested in rust-lang/miri#3080 (comment) We previously solved memory growth issues associated with the Stacked Borrows and Tree Borrows runtimes with a GC. But of course we also have state accumulation associated with whole allocations elsewhere in the interpreter, and this PR starts tackling those. To do this, we expand the visitor for the GC so that it can visit a BorTag or an AllocId. Instead of collecting all live AllocIds into a single HashSet, we just collect from the Machine itself then go through an accessor `InterpCx::is_alloc_live` which checks a number of allocation data structures in the core interpreter. This avoids the overhead of all the inserts that collecting their keys would require. r? ``@RalfJung``

rustbot assigned RalfJung Nov 18, 2023

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Extend the BorTag GC to AllocIds rust-lang/miri#3103

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saethlin force-pushed the allocid-gc branch from 86712fd to 1c23cab Compare November 18, 2023 04:11

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Test that the GC consults the extra_fn_ptr map

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Test with -Zmiri-provenance-gc=1 on Linux

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Rollup of 7 pull requests #118122

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Rollup of 6 pull requests #118134

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Expand Miri's BorTag GC to a Provenance GC #118029

Expand Miri's BorTag GC to a Provenance GC #118029

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