Run a new workload using BOLT and merge the results

Overview

In this step, you’ll generate a profile for a write-heavy workload and merge it with the read-heavy profile you created earlier. The merged profile captures a broader set of execution behaviors for optimizing the final binary.

Run a write-only workload for the application binary

You can reuse the previously built MySQL binary or generate a new instrumented variant if needed.

Use the BOLT-instrumented MySQL binary to run a write-only workload and generate profile-writeonly.fdata. You can reuse the binary from the previous step or create a new one with the command below.

    

        
        
llvm-bolt $HOME/mysql-server/build/bin/mysqld \
  -instrument \
  -o $HOME/mysql-server/build/bin/mysqldwriteonly.instrumented \
  --instrumentation-file=$HOME/mysql-server/build/profile-writeonly.fdata \
  --instrumentation-sleep-time=5 \
  --instrumentation-no-counters-clear \
  --instrumentation-wait-forks \
  2>&1 | tee $HOME/mysql-server/bolt-instrumentation-writeonly.log

    

Run the write-only workload

Run Sysbench using the write-only Lua script to generate a workload profile:

    

        
        
# On an 8-core system, use available cores (e.g., 7 for Sysbench)
taskset -c 7 ./src/sysbench \
  --db-driver=mysql \
  --mysql-host=127.0.0.1 \
  --mysql-db=bench \
  --mysql-user=bench \
  --mysql-password=bench \
  --mysql-port=3306 \
  --tables=8 \
  --table-size=10000 \
  --forced-shutdown \
  --report-interval=60 \
  --rand-type=uniform \
  --time=5 \
  --threads=1 \
  --simple-ranges=1 \
  --distinct-ranges=1 \
  --sum-ranges=1 \
  --order-ranges=1 \
  --point-selects=10 \
  src/lua/oltp_write_only.lua run

    

Confirm that --instrumentation-file is set to profile-writeonly.fdata.

Reset the dataset after profiling

After running each benchmark, cleanly shut down the MySQL server and reset the in-memory dataset to ensure the next run starts in a consistent state:

    

        
        
./bin/mysqladmin -u root shutdown ; rm -rf /dev/shm/dataset ; cp -R data/ /dev/shm/dataset

    

Verify that both profiles exist

Verify that the following .fdata files have been generated:

    

        
        
ls -lh $HOME/mysql-server/build/profile-readonly.fdata
ls -lh $HOME/mysql-server/build/profile-writeonly.fdata

    

Merge the read and write profiles

Both .fdata files should now exist and contain valid data:

• profile-readonly.fdata
• profile-writeonly.fdata

Merge the feature profiles

Use merge-fdata to combine the feature-specific profiles into one comprehensive .fdata file:

    

        
        
merge-fdata $HOME/mysql-server/build/profile-readonly.fdata $HOME/mysql-server/build/profile-writeonly.fdata \
  -o $HOME/mysql-server/build/profile-merged.fdata

    

Output:

    

        
        
Using legacy profile format.
Profile from 2 files merged.

    

This creates a single merged profile (profile-merged.fdata) covering both read-only and write-only workload behaviors.

Verify the merged profile

Confirm the merged profile file exists and is non-empty:

    

        
        
ls -lh $HOME/mysql-server/build/profile-merged.fdata

    

Optimize the binary with the merged profile

Use LLVM-BOLT to generate the final optimized binary using the merged .fdata file:

    

        
        
llvm-bolt $HOME/mysql-server/build/bin/mysqld \
  -o $HOME/mysql-server/build/bin/mysqldreadwrite_merged.bolt_instrumentation \
  -data=$HOME/mysql-server/build/profile-merged.fdata \
  -reorder-blocks=ext-tsp \
  -reorder-functions=hfsort \
  -split-functions \
  -split-all-cold \
  -split-eh \
  -dyno-stats \
  --print-profile-stats \
  2>&1 | tee $HOME/mysql-server/build/bolt-readwritemerged-opt.log

    

This command optimizes the binary layout based on the merged workload profile, creating a single binary (mysqldreadwrite_merged.bolt_instrumentation) that is optimized across both features.