cloud-hypervisor/docs/heap-profiling.md

Heap profiling

Cloud Hypervisor supports generating a profile using dhat of the heap allocations made during the runtime of the process.

Building a suitable binary

This adds the symbol information to the release binary but does not otherwise affect the performance.

$ cargo build --profile profiling --features "dhat-heap"

Generating output

Cloud Hypervisor can then be run as usual. However it is necessary to run with --seccomp false as the profiling requires extra syscalls.

$ target/profiling/cloud-hypervisor \
        --kernel ~/src/linux/vmlinux \
        --pmem file=~/workloads/focal.raw \
        --cpus boot=1 --memory size=1G \
        --cmdline "root=/dev/pmem0p1 console=ttyS0" \
        --serial tty --console off \
        --api-socket /tmp/api1 \
        --seccomp false

When the VMM exits a message like the following will be shown:

dhat: Total:     384,582 bytes in 3,512 blocks
dhat: At t-gmax: 133,885 bytes in 379 blocks
dhat: At t-end:  12,160 bytes in 20 blocks
dhat: The data has been saved to dhat-heap.json, and is viewable with dhat/dh_view.html

The JSON output can then be uploaded to the dh_view tool for analysis.