linux: thread 'main' panicked at 'attempt to subtract with overflow'

[parkr]

Hi! I just pulled & re-compiled at 5f7b361 and got a funky error! Looks like something funky with rbspy::SampleTime::get_sleep_time – maybe related to #79?

~/rbspy$ git rev-parse HEAD
5f7b3615277978d8e50dc335cdfdbb4910e8ddc9
~/massive-jekyll-site$ rustc --version
rustc 1.23.0 (766bd11c8 2018-01-01)
~/rbspy$ which ruby
/usr/bin/ruby
~/massive-jekyll-site$ ruby --version
ruby 2.3.3p222 (2016-11-21) [x86_64-linux-gnu]
~/massive-jekyll-site$ RUST_BACKTRACE=1 ~/rbspy/target/debug/rbspy record /home/parker/jekyll/exe/jekyll build
Recording data to /home/parker/.cache/rbspy/records/rbspy-2018-01-31-Jgn67RAD6i.txt
Press Ctrl+C to stop
Configuration file: none
            Source: /home/parker/massive-jekyll-site
       Destination: /home/parker/massive-jekyll-site/_site
 Incremental build: disabled. Enable with --incremental
      Generating...
thread 'main' panicked at 'attempt to subtract with overflow', src/main.rs:224:9
stack backtrace:
   0: std::sys::imp::backtrace::tracing::imp::unwind_backtrace
             at /checkout/src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::_print
             at /checkout/src/libstd/sys_common/backtrace.rs:68
   2: std::panicking::default_hook::{{closure}}
             at /checkout/src/libstd/sys_common/backtrace.rs:57
             at /checkout/src/libstd/panicking.rs:381
   3: std::panicking::default_hook
             at /checkout/src/libstd/panicking.rs:397
   4: std::panicking::rust_panic_with_hook
             at /checkout/src/libstd/panicking.rs:577
   5: std::panicking::begin_panic
             at /checkout/src/libstd/panicking.rs:538
   6: std::panicking::begin_panic_fmt
             at /checkout/src/libstd/panicking.rs:522
   7: rust_begin_unwind
             at /checkout/src/libstd/panicking.rs:498
   8: core::panicking::panic_fmt
             at /checkout/src/libcore/panicking.rs:71
   9: core::panicking::panic
             at /checkout/src/libcore/panicking.rs:51
  10: rbspy::SampleTime::get_sleep_time
             at src/main.rs:224
  11: rbspy::record
             at src/main.rs:292
  12: rbspy::do_main
             at src/main.rs:138
  13: rbspy::main
             at src/main.rs:169
  14: __rust_maybe_catch_panic
             at /checkout/src/libpanic_unwind/lib.rs:101
  15: std::rt::lang_start
             at /checkout/src/libstd/panicking.rs:459
             at /checkout/src/libstd/panic.rs:365
             at /checkout/src/libstd/rt.rs:58
  16: main
  17: __libc_start_main
  18: _start

[jvns]

thanks for the report! let me know if you have thoughts about the approach to fix it in #83

[parkr]

When I apply #83, it works!

parker@kondwani:~/massive-jekyll-site$ RUST_BACKTRACE=1 ~/rbspy/target/debug/rbspy record /home/parker/jekyll/exe/jekyll build
Recording data to /home/parker/.cache/rbspy/records/rbspy-2018-01-31-5wJJnuSV30.txt
Press Ctrl+C to stop
Behind expected sample time by 210183 nanoseconds, results may be inaccurate. Try sampling at a lower rate
Configuration file: none
            Source: /home/parker/massive-jekyll-site
       Destination: /home/parker/massive-jekyll-site/_site
 Incremental build: disabled. Enable with --incremental
      Generating...
                    done in 54.053 seconds.
 Auto-regeneration: disabled. Use --watch to enable.
Writing flamegraph to /home/parker/.cache/rbspy/records/rbspy-2018-01-31-5wJJnuSV30.svg

By the way I setup a simple static file server at https://rbspy.parkermakes.tools so you can view all my profiles! The one above is at: https://rbspy.parkermakes.tools/rbspy-2018-01-31-5wJJnuSV30.svg

[jvns]

that's so cool! how is hunting for possible perf improvements in jekyll going?

[parkr]

how is hunting for possible perf improvements in jekyll going?

good! i managed to take a site with 10,000 posts from 150s down to 54s, based on this: https://rbspy.parkermakes.tools/rbspy-2018-01-30-o4qFcKDwSo.svg

[jvns]

whoa congratulations!! would be curious to see a link to a PR if you have one at some point, i'm collecting stories at #62