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Compress Liveness data some more. #54420

Merged
merged 1 commit into from
Sep 22, 2018
Merged

Compress Liveness data some more. #54420

merged 1 commit into from
Sep 22, 2018

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nnethercote
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Profiling shows that the (reader, writer, used) triples used by
liveness analysis almost always have invalid reader and writer
fields. We can take advantage of this knowledge to use a compressed
representation for them, falling back to a secondary table for the
uncommon cases.

This change reduces instruction counts on numerous benchmarks, the best
by 16%. It also reduces max-rss on numerous benchmarks, the best by 38%.

The patch also renames these triples from Users to RWU, because it's
confusing having a type whose name is plural and then used within
vectors whose names are also plural.

r? @nikomatsakis

@nnethercote
Compress Liveness data some more.
b2f25e3 
Profiling shows that the `(reader, writer, used)` triples used by
liveness analysis almost always have invalid `reader` and `writer`
fields. We can take advantage of this knowledge to use a compressed
representation for them, falling back to a secondary table for the
uncommon cases.

This change reduces instruction counts on numerous benchmarks, the best
by 16%. It also reduces max-rss on numerous benchmarks, the best by 38%.

The patch also renames these triples from `Users` to `RWU`, because it's
confusing having a type whose name is plural and then used within
vectors whose names are also plural.
@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Sep 21, 2018
@nnethercote
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I know I just changed this code in #54211, but I came up with this better way of handling things and couldn't resist trying. It worked better than I expected. Instruction counts:

keccak-check
        avg: -5.0%      min: -16.2%     max: -1.2%
keccak-debug
        avg: -6.1%      min: -14.0%     max: -1.5%
keccak-opt
        avg: -5.5%      min: -14.0%     max: -1.2%
inflate-check
        avg: -2.4%      min: -8.3%      max: -0.9%
inflate-opt
        avg: -2.0%?     min: -6.8%?     max: -0.3%?
inflate-debug
        avg: -2.6%      min: -6.4%      max: -1.3%
clap-rs-check
        avg: -2.4%      min: -4.7%      max: -0.8%
clap-rs-debug
        avg: -2.6%      min: -3.7%      max: -2.0%
clap-rs-opt
        avg: -1.5%      min: -2.5%      max: -1.0%

max-rss:

keccak-check
        avg: -27.4%     min: -38.7%     max: -0.1%
keccak-debug
        avg: -12.7%     min: -38.0%     max: 0.0%
keccak-opt
        avg: -12.7%     min: -38.0%     max: 0.0%
inflate-check
        avg: -6.2%      min: -18.4%     max: 0.2%
inflate-opt
        avg: -2.1%?     min: -9.3%?     max: 0.6%?
inflate-debug
        avg: -1.6%      min: -8.8%      max: 1.6%
clap-rs-debug
        avg: 1.6%       min: -0.6%      max: 7.2%
clap-rs-opt
        avg: -1.4%      min: -6.6%      max: 0.8%
clap-rs-check
        avg: -0.6%      min: -0.9%      max: -0.1%

I also tried a different representation, where each packed RWU was a single byte and the secondary table was an FxHashMap. It saved some more memory, but the instruction counts and wall-times were a bit higher, so I finalized on this vector approach.

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@bors try

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bors commented Sep 21, 2018

⌛ Trying commit b2f25e3 with merge b77797424ed915239023046f4894ca3d3f60d2c3...

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BTW, although the benefits (esp. max-rss) mostly accrue to non-NLL builds, the NLL builds do get some improvement.

@nnethercote nnethercote mentioned this pull request Sep 21, 2018
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bors commented Sep 21, 2018

☀️ Test successful - status-travis
State: approved= try=True

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@bors r+

@nnethercote what do you think about trying to rewrite this pass altogether to operate on MIR? By this point you've about rewritten it already a few times. =)

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bors commented Sep 21, 2018

📌 Commit b2f25e3 has been approved by nikomatsakis

@bors 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 Sep 21, 2018
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LOL, I could give it a try, though you said previously that @wesleywiser was interested and I wouldn't want to steal it from them.

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wesleywiser commented Sep 21, 2018 •
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@nnethercote Please, feel free to take that :) I've got a couple other things on my plate at the moment. I'll get to it at some point if you don't.

pietroalbini added a commit to pietroalbini/rust that referenced this pull request Sep 22, 2018
@pietroalbini
Rollup merge of rust-lang#54420 - nnethercote:PackedRWU-Vec, r=nikoma…
317b212 
…tsakis

Compress `Liveness` data some more.

Profiling shows that the `(reader, writer, used)` triples used by
liveness analysis almost always have invalid `reader` and `writer`
fields. We can take advantage of this knowledge to use a compressed
representation for them, falling back to a secondary table for the
uncommon cases.

This change reduces instruction counts on numerous benchmarks, the best
by 16%. It also reduces max-rss on numerous benchmarks, the best by 38%.

The patch also renames these triples from `Users` to `RWU`, because it's
confusing having a type whose name is plural and then used within
vectors whose names are also plural.

r? @nikomatsakis
@pietroalbini pietroalbini mentioned this pull request Sep 22, 2018
Merged
bors added a commit that referenced this pull request Sep 22, 2018
@bors
Auto merge of #54457 - pietroalbini:rollup, r=pietroalbini
5929185 
Rollup of 16 pull requests

Successful merges:

 - #53652 (define copy_within on slices)
 - #54261 (Make `dyn` a keyword in the 2018 edition)
 - #54280 (remove (more) CAS API from Atomic* types where not natively supported)
 - #54323 (rustbuild: drop color handling)
 - #54350 (Support specifying edition in doc test)
 - #54370 (Improve handling of type bounds in `bit_set.rs`.)
 - #54371 (add -Zui-testing to rustdoc)
 - #54374 (Make 'proc_macro::MultiSpan' public.)
 - #54402 (Use no_default_libraries for all NetBSD flavors)
 - #54409 (Detect `for _ in in bar {}` typo)
 - #54412 (add applicability to span_suggestion call)
 - #54413 (Add UI test for deref recursion limit printing twice)
 - #54415 (parser: Tweak function parameter parsing to avoid rollback on succesfull path)
 - #54420 (Compress `Liveness` data some more.)
 - #54422 (Simplify slice's first(_mut) and last(_mut) with get)
 - #54446 (Unify christianpoveda's emails)

Failed merges:

 - #54058 (Introduce the partition_dedup/by/by_key methods for slices)

r? @ghost
bors added a commit that referenced this pull request Sep 22, 2018
@bors
Auto merge of #54457 - pietroalbini:rollup, r=pietroalbini
af50e38 
Rollup of 16 pull requests

Successful merges:

 - #53652 (define copy_within on slices)
 - #54261 (Make `dyn` a keyword in the 2018 edition)
 - #54280 (remove (more) CAS API from Atomic* types where not natively supported)
 - #54323 (rustbuild: drop color handling)
 - #54350 (Support specifying edition in doc test)
 - #54370 (Improve handling of type bounds in `bit_set.rs`.)
 - #54371 (add -Zui-testing to rustdoc)
 - #54374 (Make 'proc_macro::MultiSpan' public.)
 - #54402 (Use no_default_libraries for all NetBSD flavors)
 - #54409 (Detect `for _ in in bar {}` typo)
 - #54412 (add applicability to span_suggestion call)
 - #54413 (Add UI test for deref recursion limit printing twice)
 - #54415 (parser: Tweak function parameter parsing to avoid rollback on succesfull path)
 - #54420 (Compress `Liveness` data some more.)
 - #54422 (Simplify slice's first(_mut) and last(_mut) with get)
 - #54446 (Unify christianpoveda's emails)

Failed merges:

 - #54058 (Introduce the partition_dedup/by/by_key methods for slices)

r? @ghost
@bors bors merged commit b2f25e3 into rust-lang:master Sep 22, 2018
@nnethercote nnethercote deleted the PackedRWU-Vec branch September 23, 2018 20:54
@nnethercote
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Perf results look good, as expected.

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@nikomatsakis nikomatsakis nikomatsakis approved these changes

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@nnethercote @bors @nikomatsakis @wesleywiser @rust-highfive