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100% CPU usage when running doc tests #128538

@tingerrr

Description

@tingerrr

The Problem

Since a while, and I don't know since when, running any variant of cargo test --doc puts my CPU at 100% so hard, that it crashes my PC if I don't Ctrl+C early enough. Running other tests works just fine, namely unit tests, I haven't tried running any integration tests.

I expected to see this happen:
It runs the doc tests basically as fast as regular tests.

Instead, this happened:
My PC locks up and sometimes crashes.

Meta

Toolchains

I tried this on various versions, and it has persisted across all of them:

  • 1.82-nightly
    rustc 1.82.0-nightly (612a33f20 2024-07-29) binary: rustc commit-hash: 612a33f20b9b2c27380edbc4b26a01433ed114bc commit-date: 2024-07-29 host: x86_64-unknown-linux-gnu release: 1.82.0-nightly LLVM version: 18.1.7 
  • 1.80-stable
    rustc 1.80.0 (051478957 2024-07-21) binary: rustc commit-hash: 051478957371ee0084a7c0913941d2a8c4757bb9 commit-date: 2024-07-21 host: x86_64-unknown-linux-gnu release: 1.80.0 LLVM version: 18.1.7 
  • 1.79.1-stable
    • Don't have it installed anymore.
  • rustc 1.74.1
    rustc 1.74.1 (a28077b28 2023-12-04) binary: rustc commit-hash: a28077b28a02b92985b3a3faecf92813155f1ea1 commit-date: 2023-12-04 host: x86_64-unknown-linux-gnu release: 1.74.1 LLVM version: 17.0.4 

Repositories

I have tried this on various repositories like:

  • cargo +1.80 test --doc --workspace on typst-test#a8aea584, fails on the typst-test-lib crate
  • cargo +1.74.1 test --doc --workspace on typst-test#599717fc, fails on the typst-test-lib crate
  • cargo +1.80 test --doc --workspace on helix#3fcf168c, fails mostly on the helix-tui crate
  • cargo +1.80 test --doc --workspace on typst#c4dd6fa0, largely doesn't fail, due to the lack of runnable tests

Hardware

This happens consistently on two PCs:

PC 1

Linux twinkbook 6.10.2-arch1-1 #1 SMP PREEMPT_DYNAMIC Sat, 27 Jul 2024 16:49:55 +0000 x86_64 GNU/Linux

Output of lscpu:

Architecture: x86_64 CPU op-mode(s): 32-bit, 64-bit Address sizes: 39 bits physical, 48 bits virtual Byte Order: Little Endian CPU(s): 8 On-line CPU(s) list: 0-7 Vendor ID: GenuineIntel Model name: 11th Gen Intel(R) Core(TM) i7-1165G7 @ 2.80GHz CPU family: 6 Model: 140 Thread(s) per core: 2 Core(s) per socket: 4 Socket(s): 1 Stepping: 1 CPU(s) scaling MHz: 24% CPU max MHz: 4700,0000 CPU min MHz: 400,0000 BogoMIPS: 5608,00 Flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse 36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc art arch_perfmon pebs bts rep_good nopl xtopo logy nonstop_tsc cpuid aperfmperf tsc_known_freq pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdr and lahf_lm abm 3dnowprefetch cpuid_fault epb cat_l2 cdp_l2 ssbd ibrs ibpb stibp ibrs_enhanced tpr_shadow flexpriority ept vpid ept_ad fsg sbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid rdt_a avx512f avx51 2dq rdseed adx smap avx512ifma clflushopt clwb intel_pt avx512cd sha_ ni avx512bw avx512vl xsaveopt xsavec xgetbv1 xsaves split_lock_detect user_shstk dtherm ida arat pln pts hwp hwp_notify hwp_act_window hwp _epp hwp_pkg_req vnmi avx512vbmi umip pku ospke avx512_vbmi2 gfni vae s vpclmulqdq avx512_vnni avx512_bitalg avx512_vpopcntdq rdpid movdiri movdir64b fsrm avx512_vp2intersect md_clear ibt flush_l1d arch_capab ilities Virtualization features: Virtualization: VT-x Caches (sum of all): L1d: 192 KiB (4 instances) L1i: 128 KiB (4 instances) L2: 5 MiB (4 instances) L3: 12 MiB (1 instance) NUMA: NUMA node(s): 1 NUMA node0 CPU(s): 0-7 Vulnerabilities: Gather data sampling: Mitigation; Microcode Itlb multihit: Not affected L1tf: Not affected Mds: Not affected Meltdown: Not affected Mmio stale data: Not affected Reg file data sampling: Not affected Retbleed: Not affected Spec rstack overflow: Not affected Spec store bypass: Mitigation; Speculative Store Bypass disabled via prctl Spectre v1: Mitigation; usercopy/swapgs barriers and __user pointer sanitization Spectre v2: Mitigation; Enhanced / Automatic IBRS; IBPB conditional; RSB filling; PBRSB-eIBRS SW sequence; BHI SW loop, KVM SW loop Srbds: Not affected Tsx async abort: Not affected 

PC 2

Linux hsh 6.10.0-arch1-2 #1 SMP PREEMPT_DYNAMIC Mon, 22 Jul 2024 17:28:23 +0000 x86_64 GNU/Linux

Output of lscpu:

Architecture: x86_64 CPU op-mode(s): 32-bit, 64-bit Address sizes: 39 bits physical, 48 bits virtual Byte Order: Little Endian CPU(s): 8 On-line CPU(s) list: 0-7 Vendor ID: GenuineIntel Model name: Intel(R) Core(TM) i7-7700K CPU @ 4.20GHz CPU family: 6 Model: 158 Thread(s) per core: 2 Core(s) per socket: 4 Socket(s): 1 Stepping: 9 CPU(s) scaling MHz: 18% CPU max MHz: 4500.0000 CPU min MHz: 800.0000 BogoMIPS: 8403.00 Flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc art arch_perfmon pebs bts rep_good nopl xto pology nonstop_tsc cpuid aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault pti ssbd ibrs ibpb stibp tpr_shadow flexpriority ept vpid ept_ad fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid mpx rdseed adx smap clflushopt intel_pt xsaveopt xsavec xgetbv1 xsaves dtherm ida arat pln pts hwp hwp_notify hwp_act_window hwp_epp vnmi md_clear flush_l1d arch_capabilities Virtualization features: Virtualization: VT-x Caches (sum of all): L1d: 128 KiB (4 instances) L1i: 128 KiB (4 instances) L2: 1 MiB (4 instances) L3: 8 MiB (1 instance) NUMA: NUMA node(s): 1 NUMA node0 CPU(s): 0-7 Vulnerabilities: Gather data sampling: Mitigation; Microcode Itlb multihit: KVM: Mitigation: VMX disabled L1tf: Mitigation; PTE Inversion; VMX conditional cache flushes, SMT vulnerable Mds: Mitigation; Clear CPU buffers; SMT vulnerable Meltdown: Mitigation; PTI Mmio stale data: Mitigation; Clear CPU buffers; SMT vulnerable Reg file data sampling: Not affected Retbleed: Mitigation; IBRS Spec rstack overflow: Not affected Spec store bypass: Mitigation; Speculative Store Bypass disabled via prctl Spectre v1: Mitigation; usercopy/swapgs barriers and __user pointer sanitization Spectre v2: Mitigation; IBRS; IBPB conditional; STIBP conditional; RSB filling; PBRSB-eIBRS Not affected; BHI Not affected Srbds: Mitigation; Microcode Tsx async abort: Mitigation; TSX disabled 

I'll happily add more info if requested.

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    A-doctestsArea: Documentation tests, run by rustdocC-bugCategory: This is a bug.I-compiletimeIssue: Problems and improvements with respect to compile times.S-needs-reproStatus: This issue has no reproduction and needs a reproduction to make progress.T-rustdocRelevant to the rustdoc team, which will review and decide on the PR/issue.perf-regressionPerformance regression.regression-untriagedUntriaged performance or correctness regression.

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