Re: [Libguestfs] [PATCH nbdkit 1/4] common/utils/test-vector.c: Add vector benchmarks

The generic vector reallocs on every append. Add benchmarks to measure the cost with uint32 vector (used for copying extents) and the effect of reserving space upfront. The tests show that realloc is pretty efficient, but calling reserve before the appends speeds the appends up significantly. NBDKIT_BENCH=1 ./test-vector bench_reserve: 1000000 appends in 0.004503 s bench_append: 1000000 appends in 0.014986 s The new benchmarks do not run by default to avoid trouble in CI on overloaded machines or under qemu emulation. A new target added to run all benchmaks: make bench Ported from libnbd: - https://listman.redhat.com/archives/libguestfs/2021-October/msg00304.html - https://listman.redhat.com/archives/libguestfs/2021-October/msg00305.html --- Makefile.am | 5 +++ README | 7 ++++ common/utils/Makefile.am | 3 ++ common/utils/bench.h | 72 ++++++++++++++++++++++++++++++++++++++