Improve speed of JPEG reading #131

mcroomp · 2025-01-05T17:17:01Z

Improve speed of JPEG reading

Best devli ever (sorry @Melirius ) (also helps that (1 << bits) - 1 is recycled from BitReader::read)
Consistently use 32 bit math to avoid unnecessary widen/narrow conversions
Optimistically fill 8 byte fill register so that branching generally only happens in one location
Use LeptonError in BitReader to avoid unnecessary error conversions, since LeptonError is as small as std::io::Error now

Copilot

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

Comments suppressed due to low confidence (6)

src/jpeg/bit_reader.rs:62

[nitpick] The change from returning u16 to u32 in the read function should be reviewed for consistency and correctness.

pub fn read(&mut self, bits_to_read: u32) -> Result<u32> {

src/jpeg/bit_reader.rs:62

Ensure that the new behavior introduced in the read function is covered by tests.

pub fn read(&mut self, bits_to_read: u32) -> Result<u32> {

src/helpers.rs:105

The condition (value << 1) > shifted might not correctly handle edge cases where value is close to the maximum value for u32. Consider using value & (shifted >> 1) != 0 as in the original code.

if (value << 1) > shifted {

src/jpeg/jpeg_read.rs:687

The conversion of the result of bit_reader.read(1)? to usize should be carefully reviewed to ensure it does not introduce any issues.

node = ctree.node[usize::from(node)][bit_reader.read(1)? as usize];

src/jpeg/jpeg_read.rs:903

The change from u16 to u32 in the decode_eobrun_bits function should be reviewed to ensure it does not introduce any issues.

fn decode_eobrun_bits(s: u8, n: u32) -> u32 {

src/jpeg/jpeg_read.rs:722

The conversion of literal_bits to u32 in the read_dc function should be reviewed to ensure it does not introduce any issues.

let value = bit_reader.read(literal_bits)?;

Melirius · 2025-01-06T10:38:50Z

lib/src/jpeg/bit_reader.rs

+    /// with as many bits as possible, leaving the possibility of unwinding via the undo_read_ahead
+    /// function in certain corner cases.
+    #[inline(never)]
+    #[cold]


Is this really helps with performance? By the rule of thumb refill should be a bit too frequent to being cold. I'll check on my box.

The tradeoff was with having more registers free for the inner loop, but it's possible that it's faster without the cold. fill_register is definitely cold since it gets called almost never.

With cold:

ivan@ivan-5950:~/lepton_jpeg_rust$ sudo rm images/img_52MP_7k2.lep; sudo perf stat -B -e cache-references,cache-misses,cycles,ic_fetch_stall.ic_stall_back_pressure,stalled-cycles-frontend,instructions,branch-instructions,branch-misses,ic_fetch_stall.ic_stall_any,ic_fetch_stall.ic_stall_dq_empty,l2_cache_misses_from_ic_miss,l2_latency.l2_cycles_waiting_on_fills,faults,migrations taskset -c 10 nice -n -20 target/release/lepton_jpeg_util images/img_52MP_7k.jpg images/img_52MP_7k2.lep 2025-01-12T14:26:43.217Z INFO [lepton_jpeg::structs::lepton_file_writer] compressing to Lepton format 2025-01-12T14:26:43.583Z INFO [lepton_jpeg::structs::lepton_file_writer] Number of threads: 8 2025-01-12T14:26:44.712Z INFO [lepton_jpeg::structs::lepton_file_writer] worker threads 7732ms of CPU time in 1127ms of wall time 2025-01-12T14:26:44.712Z INFO [lepton_jpeg::structs::lepton_file_writer] decompressing to verify contents 2025-01-12T14:26:46.304Z INFO [lepton_jpeg_util] compressed input 22171278, output 17324074 bytes (compression = 28.0%) 2025-01-12T14:26:46.304Z INFO [lepton_jpeg_util] Main thread CPU: 3095ms, Worker thread CPU: 18774 ms, walltime: 3095 ms Performance counter stats for 'taskset -c 10 nice -n -20 target/release/lepton_jpeg_util images/img_52MP_7k.jpg images/img_52MP_7k2.lep': 857 527 770 cache-references (25,32%) 76 481 649 cache-misses # 8,92% of all cache refs (25,47%) 14 095 457 313 cycles (25,47%) 865 595 905 ic_fetch_stall.ic_stall_back_pressure (25,51%) 935 546 969 stalled-cycles-frontend # 6,64% frontend cycles idle (25,31%) 34 775 075 664 instructions # 2,47 insn per cycle # 0,03 stalled cycles per insn (25,24%) 3 665 427 290 branch-instructions (25,05%) 140 713 890 branch-misses # 3,84% of all branches (25,07%) 5 325 860 720 ic_fetch_stall.ic_stall_any (25,28%) 39 528 616 ic_fetch_stall.ic_stall_dq_empty (25,38%) 62 527 706 l2_cache_misses_from_ic_miss (25,24%) 1 842 115 928 l2_latency.l2_cycles_waiting_on_fills (25,12%) 188 277 faults 1 migrations 3,129010978 seconds time elapsed 2,821312000 seconds user 0,302604000 seconds sys

Without cold:

ivan@ivan-5950:~/lepton_jpeg_rust$ sudo rm images/img_52MP_7k2.lep; sudo perf stat -B -e cache-references,cache-misses,cycles,ic_fetch_stall.ic_stall_back_pressure,stalled-cycles-frontend,instructions,branch-instructions,branch-misses,ic_fetch_stall.ic_stall_any,ic_fetch_stall.ic_stall_dq_empty,l2_cache_misses_from_ic_miss,l2_latency.l2_cycles_waiting_on_fills,faults,migrations taskset -c 10 nice -n -20 target/release/lepton_jpeg_util images/img_52MP_7k.jpg images/img_52MP_7k2.lep 2025-01-12T14:25:52.492Z INFO [lepton_jpeg::structs::lepton_file_writer] compressing to Lepton format 2025-01-12T14:25:52.974Z INFO [lepton_jpeg::structs::lepton_file_writer] Number of threads: 8 2025-01-12T14:25:54.453Z INFO [lepton_jpeg::structs::lepton_file_writer] worker threads 10251ms of CPU time in 1478ms of wall time 2025-01-12T14:25:54.453Z INFO [lepton_jpeg::structs::lepton_file_writer] decompressing to verify contents 2025-01-12T14:25:56.028Z INFO [lepton_jpeg_util] compressed input 22171278, output 17324074 bytes (compression = 28.0%) 2025-01-12T14:25:56.028Z INFO [lepton_jpeg_util] Main thread CPU: 3547ms, Worker thread CPU: 21139 ms, walltime: 3547 ms Performance counter stats for 'taskset -c 10 nice -n -20 target/release/lepton_jpeg_util images/img_52MP_7k.jpg images/img_52MP_7k2.lep': 854 375 836 cache-references (25,26%) 74 116 401 cache-misses # 8,67% of all cache refs (25,55%) 14 048 593 475 cycles (25,55%) 487 211 314 ic_fetch_stall.ic_stall_back_pressure (25,48%) 869 359 514 stalled-cycles-frontend # 6,19% frontend cycles idle (25,31%) 35 076 159 662 instructions # 2,50 insn per cycle # 0,02 stalled cycles per insn (25,18%) 3 638 127 413 branch-instructions (25,14%) 140 480 887 branch-misses # 3,86% of all branches (25,13%) 5 203 535 058 ic_fetch_stall.ic_stall_any (25,11%) 36 559 121 ic_fetch_stall.ic_stall_dq_empty (24,97%) 61 473 795 l2_cache_misses_from_ic_miss (24,92%) 1 770 575 776 l2_latency.l2_cycles_waiting_on_fills (24,98%) 188 278 faults 1 migrations 3,585066548 seconds time elapsed 3,233798000 seconds user 0,346549000 seconds sys

Melirius · 2025-01-06T10:45:25Z

Nice work, congrats to speed up devli more!

Melirius · 2025-01-12T14:35:07Z

But main is faster (all compiled on rustc 1.81.0 (eeb90cda1 2024-09-04) with RUSTFLAGS='-C target-feature=+avx2 -C target-feature=+lzcnt' cargo build --release):

ivan@ivan-5950:~/lepton_jpeg_rust$ sudo rm images/img_52MP_7k2.lep; sudo perf stat -B -e cache-references,cache-misses,cycles,ic_fetch_stall.ic_stall_back_pressure,stalled-cycles-frontend,instructions,branch-instructions,branch-misses,ic_fetch_stall.ic_stall_any,ic_fetch_stall.ic_stall_dq_empty,l2_cache_misses_from_ic_miss,l2_latency.l2_cycles_waiting_on_fills,faults,migrations taskset -c 10 nice -n -20 target/release/lepton_jpeg_util images/img_52MP_7k.jpg images/img_52MP_7k2.lep
2025-01-12T14:30:24.018Z INFO  [lepton_jpeg::structs::lepton_file_writer] compressing to Lepton format
2025-01-12T14:30:24.455Z INFO  [lepton_jpeg::structs::lepton_file_writer] Number of threads: 8
2025-01-12T14:30:25.763Z INFO  [lepton_jpeg::structs::lepton_file_writer] worker threads 9133ms of CPU time in 1306ms of wall time
2025-01-12T14:30:25.763Z INFO  [lepton_jpeg::structs::lepton_file_writer] decompressing to verify contents
2025-01-12T14:30:27.342Z INFO  [lepton_jpeg_util] compressed input 22171278, output 17324074 bytes (compression = 28.0%)
2025-01-12T14:30:27.342Z INFO  [lepton_jpeg_util] Main thread CPU: 3335ms, Worker thread CPU: 20100 ms, walltime: 3335 ms

 Performance counter stats for 'taskset -c 10 nice -n -20 target/release/lepton_jpeg_util images/img_52MP_7k.jpg images/img_52MP_7k2.lep':

       858 748 386      cache-references                                                        (25,06%)
        74 830 355      cache-misses                     #    8,71% of all cache refs           (24,91%)
    13 836 453 808      cycles                                                                  (24,97%)
       777 193 113      ic_fetch_stall.ic_stall_back_pressure                                        (25,21%)
       920 473 108      stalled-cycles-frontend          #    6,65% frontend cycles idle        (25,37%)
    35 558 555 176      instructions                     #    2,57  insn per cycle            
                                                  #    0,03  stalled cycles per insn     (25,47%)
     3 646 640 572      branch-instructions                                                     (25,51%)
       129 001 386      branch-misses                    #    3,54% of all branches             (25,43%)
     4 922 193 512      ic_fetch_stall.ic_stall_any                                             (25,37%)
        33 547 664      ic_fetch_stall.ic_stall_dq_empty                                        (25,23%)
        64 219 569      l2_cache_misses_from_ic_miss                                            (25,19%)
     1 720 951 168      l2_latency.l2_cycles_waiting_on_fills                                        (25,14%)
           188 227      faults                                                                
                 1      migrations                                                            

       3,373385487 seconds time elapsed

       3,000880000 seconds user
       0,369615000 seconds sys

Similar results I got on my Intel laptop. Maybe you use different RUST version?

UPD: The same on rustc 1.84.0 (9fc6b4312 2025-01-07)

github-actions · 2025-10-23T07:45:35Z

Test Results

8 tests - 163 7 ✅ - 164 1s ⏱️ - 19m 7s
1 suites - 2 0 💤 ± 0
1 files ± 0 1 ❌ + 1

For more details on these failures, see this check.

Results for commit 2c98bb2. ± Comparison against base commit 621555c.

This pull request removes 163 tests.

lepton_jpeg ‑ jpeg::jpeg_read::tests::test_benchmark_read_block
lepton_jpeg ‑ jpeg::jpeg_read::tests::test_benchmark_read_jpeg
lepton_jpeg ‑ jpeg::jpeg_write::tests::roundtrip_baseline_jpeg
lepton_jpeg ‑ jpeg::jpeg_write::tests::roundtrip_progressive_jpeg
lepton_jpeg ‑ jpeg::jpeg_write::tests::test_benchmark_write_block
lepton_jpeg ‑ jpeg::jpeg_write::tests::test_benchmark_write_jpeg
lepton_jpeg ‑ jpeg::jpeg_write::tests::test_encode_block_long_zero_cnt
lepton_jpeg ‑ jpeg::jpeg_write::tests::test_encode_block_magnitude
lepton_jpeg ‑ jpeg::jpeg_write::tests::test_encode_block_seq
lepton_jpeg ‑ jpeg::jpeg_write::tests::test_encode_block_seq_zero
…

mcroomp added 5 commits January 2, 2025 10:14

merge

febd845

added test

3f40d98

use 32 bit math generally

d0dfe82

improve comments

d954fe0

fix comment

5e01c3d

mcroomp requested review from Melirius and Copilot January 5, 2025 17:17

mcroomp changed the title ~~Devli~~ Improve speed of JPEG reading Jan 5, 2025

Copilot AI reviewed Jan 5, 2025

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Melirius reviewed Jan 6, 2025

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mcroomp added 2 commits October 10, 2025 09:33

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Improve speed of JPEG reading #131

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