Avoid hashing the key twice in `get_query()`. #66013

nnethercote · 2019-11-01T04:05:23Z

For a single-threaded parallel compiler, this reduces instruction counts
across several benchmarks, by up to 2.8%.

The commit also adds documentation about Sharded's use of FxHasher.

nnethercote · 2019-11-01T04:06:51Z

Here are the biggest instruction count changes for a parallel compiler with one thread.

packed-simd-check
        avg: -1.9%      min: -2.8%      max: -0.7%
ctfe-stress-3-check
        avg: -1.0%?     min: -1.4%?     max: -0.5%?
piston-image-check
        avg: -0.3%      min: -0.5%      max: -0.0%
serde-check
        avg: -0.3%      min: -0.5%      max: -0.1%
syn-check
        avg: -0.3%      min: -0.5%      max: -0.1%
regex-check
        avg: -0.2%      min: -0.5%      max: -0.1%
futures-check
        avg: -0.3%      min: -0.5%      max: -0.1%
webrender-check
        avg: -0.3%      min: -0.5%      max: -0.1%
ripgrep-check
        avg: -0.2%      min: -0.4%      max: -0.0%
cargo-check
        avg: -0.2%      min: -0.4%      max: -0.0%

Wall times were super-noisy as usual but appear to be slightly improved overall.

deeply-nested-check
        avg: 3.9%       min: -0.7%      max: 9.6%
coercions-check
        avg: -1.4%?     min: -7.1%?     max: 9.4%?
regression-31157-check
        avg: -1.2%      min: -7.6%      max: 3.3%
issue-46449-check
        avg: -0.4%      min: -4.9%      max: 7.4%
regex-check
        avg: 0.6%       min: -3.6%      max: 7.0%
html5ever-check
        avg: -1.8%      min: -7.0%      max: 0.8%
await-call-tree-check
        avg: 1.4%       min: -2.0%      max: 7.0%
unused-warnings-check
        avg: -2.6%      min: -6.5%      max: 0.2%
helloworld-check
        avg: 1.5%       min: -2.2%      max: 5.8%
syn-check
        avg: -0.1%      min: -4.0%      max: 5.1%
ripgrep-check
        avg: -0.2%      min: -4.5%      max: 3.5%
encoding-check
        avg: -3.7%      min: -4.2%      max: -2.9%
piston-image-check
        avg: -0.4%      min: -4.2%      max: 1.8%
tuple-stress-check
        avg: -2.7%      min: -4.1%      max: -2.0%
unify-linearly-check
        avg: 1.2%       min: -3.4%      max: 3.8%
webrender-check
        avg: -1.5%      min: -3.3%      max: 0.8%
token-stream-stress-check
        avg: -2.3%      min: -2.8%      max: -1.8%
deep-vector-check
        avg: -0.4%      min: -2.6%      max: 1.5%
futures-check
        avg: -1.3%      min: -2.4%      max: -0.1%
unicode_normalization-check
        avg: -1.7%      min: -2.2%      max: -1.3%
ctfe-stress-3-check
        avg: -1.7%?     min: -2.1%?     max: -1.4%?
wg-grammar-check
        avg: 0.3%       min: -1.3%      max: 1.6%
inflate-check
        avg: 0.3%       min: -0.5%      max: 1.4%
packed-simd-check
        avg: -1.1%      min: -1.4%      max: -0.6%
keccak-check
        avg: -0.4%      min: -1.3%      max: 0.4%
clap-rs-check
        avg: 0.7%       min: -0.4%      max: 1.3%
webr_api-check
        avg: -0.7%      min: -1.0%      max: -0.2%
ucd-check
        avg: -0.3%      min: -0.9%      max: 1.0%
cargo-check
        avg: 0.6%       min: 0.4%       max: 0.9%
cranelift-codegen-check
        avg: -0.3%      min: -0.8%      max: -0.0%
serde-check
        avg: -0.2%      min: -0.6%      max: 0.1%

Zoxc · 2019-11-01T04:25:01Z

Did you check performance for the non-parallel compiler?

nnethercote · 2019-11-01T05:06:04Z

@bors try @rust-timer queue

rust-timer · 2019-11-01T05:06:05Z

Awaiting bors try build completion

bors · 2019-11-01T05:06:14Z

⌛ Trying commit 6fb6a7b with merge 9b89036...

@Zoxc

…r=<try> Avoid hashing the key twice in `get_query()`. For a single-threaded parallel compiler, this reduces instruction counts across several benchmarks, by up to 2.8%. The commit also adds documentation about `Sharded`'s use of `FxHasher`. r? @Zoxc

bors · 2019-11-01T07:51:55Z

☀️ Try build successful - checks-azure
Build commit: 9b89036 (9b890360102b94f2008fbbfad2c9ea4122487735)

rust-timer · 2019-11-01T07:51:57Z

Queued 9b89036 with parent aa4e57c, future comparison URL.

rust-timer · 2019-11-01T17:30:51Z

Finished benchmarking try commit 9b89036, comparison URL.

nnethercote · 2019-11-01T21:47:38Z

Non-parallel performance changes are minor. ctfe-stress-3 is slightly worse, various others are tiny bit improved.

src/librustc_data_structures/sharded.rs

nnethercote · 2019-11-03T23:15:06Z

I have updated the comments as requested.

For a single-threaded parallel compiler, this reduces instruction counts across several benchmarks, by up to 2.8%. The commit also adds documentation about `Sharded`'s use of `FxHasher`.

JohnCSimon · 2019-11-09T07:53:22Z

Ping from triage:
@Zoxc Can you please review/merge this PR?
cc: @nnethercote

Zoxc · 2019-11-15T00:31:47Z

@bors r+

bors · 2019-11-15T00:31:48Z

📌 Commit 1aceaaa has been approved by Zoxc

src/librustc/ty/query/plumbing.rs

@Zoxc

…get_query, r=Zoxc Avoid hashing the key twice in `get_query()`. For a single-threaded parallel compiler, this reduces instruction counts across several benchmarks, by up to 2.8%. The commit also adds documentation about `Sharded`'s use of `FxHasher`. r? @Zoxc

@Zoxc

…get_query, r=Zoxc Avoid hashing the key twice in `get_query()`. For a single-threaded parallel compiler, this reduces instruction counts across several benchmarks, by up to 2.8%. The commit also adds documentation about `Sharded`'s use of `FxHasher`. r? @Zoxc

@ghost

Rollup of 12 pull requests Successful merges: - #65557 (rename Error::iter_chain() and remove Error::iter_sources()) - #66013 (Avoid hashing the key twice in `get_query()`.) - #66306 (Remove cannot mutate statics in initializer of another static error) - #66338 (Update mdbook.) - #66388 (Do not ICE on recovery from unmet associated type bound obligation) - #66390 (Fix ICE when trying to suggest `Type<>` instead of `Type()`) - #66391 (Do not ICE in `if` without `else` in `async fn`) - #66394 (Fix two OOM issues related to `ConstProp`) - #66398 (Remove some stack frames from `.async` calls) - #66410 (miri: helper methods for max values of machine's usize/isize) - #66418 (Link to tracking issue in HIR const-check error code description) - #66419 (Don't warn labels beginning with `_` on unused_labels lint) Failed merges: r? @ghost

@Zoxc

…get_query, r=Zoxc Avoid hashing the key twice in `get_query()`. For a single-threaded parallel compiler, this reduces instruction counts across several benchmarks, by up to 2.8%. The commit also adds documentation about `Sharded`'s use of `FxHasher`. r? @Zoxc

@ghost

Rollup of 12 pull requests Successful merges: - #65557 (rename Error::iter_chain() and remove Error::iter_sources()) - #66013 (Avoid hashing the key twice in `get_query()`.) - #66306 (Remove cannot mutate statics in initializer of another static error) - #66338 (Update mdbook.) - #66388 (Do not ICE on recovery from unmet associated type bound obligation) - #66390 (Fix ICE when trying to suggest `Type<>` instead of `Type()`) - #66391 (Do not ICE in `if` without `else` in `async fn`) - #66398 (Remove some stack frames from `.async` calls) - #66410 (miri: helper methods for max values of machine's usize/isize) - #66418 (Link to tracking issue in HIR const-check error code description) - #66419 (Don't warn labels beginning with `_` on unused_labels lint) - #66428 (Cleanup unused function) Failed merges: r? @ghost

andjo403 · 2019-12-11T07:43:47Z

@nnethercote was there some reason that the calculated hash was not used on line 107 also?
can the same trick be used in the complete
function?

nnethercote · 2019-12-11T10:18:19Z

@andjo403: I think it would work in both cases, but those code locations are much less hot, so the potential benefit is small.

rust-highfive assigned Zoxc Nov 1, 2019

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Nov 1, 2019

Zoxc reviewed Nov 2, 2019

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Zoxc reviewed Nov 2, 2019

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Avoid hashing the key twice in get_query().

1aceaaa

For a single-threaded parallel compiler, this reduces instruction counts across several benchmarks, by up to 2.8%. The commit also adds documentation about `Sharded`'s use of `FxHasher`.

nnethercote force-pushed the avoid-hashing-twice-in-get_query branch from 6fb6a7b to 1aceaaa Compare November 3, 2019 23:16

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Nov 15, 2019

Zoxc reviewed Nov 15, 2019

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JohnTitor mentioned this pull request Nov 15, 2019

Rollup of 12 pull requests #66432

Closed

JohnTitor mentioned this pull request Nov 15, 2019

Rollup of 12 pull requests #66436

Closed

JohnTitor mentioned this pull request Nov 15, 2019

Rollup of 12 pull requests #66438

Merged

bors merged commit 1aceaaa into rust-lang:master Nov 15, 2019

nnethercote deleted the avoid-hashing-twice-in-get_query branch November 17, 2019 21:59

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Avoid hashing the key twice in `get_query()`. #66013

Avoid hashing the key twice in `get_query()`. #66013

nnethercote commented Nov 1, 2019

nnethercote commented Nov 1, 2019

Zoxc commented Nov 1, 2019

nnethercote commented Nov 1, 2019

rust-timer commented Nov 1, 2019

bors commented Nov 1, 2019

bors commented Nov 1, 2019

rust-timer commented Nov 1, 2019

rust-timer commented Nov 1, 2019

nnethercote commented Nov 1, 2019

nnethercote commented Nov 3, 2019

JohnCSimon commented Nov 9, 2019

Zoxc commented Nov 15, 2019

bors commented Nov 15, 2019

andjo403 commented Dec 11, 2019

nnethercote commented Dec 11, 2019

Avoid hashing the key twice in get_query(). #66013

Avoid hashing the key twice in get_query(). #66013

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JohnCSimon commented Nov 9, 2019

Zoxc commented Nov 15, 2019

bors commented Nov 15, 2019

andjo403 commented Dec 11, 2019

nnethercote commented Dec 11, 2019

Avoid hashing the key twice in `get_query()`. #66013

Avoid hashing the key twice in `get_query()`. #66013