Actually, mimalloc and tcmalloc both show that across almost any workload they outperform glibc. It’s difficult to outperform everywhere of course, but in terms of “works best without knowing the workload a priori”, tcmalloc and mimalloc should handily trounce glibc. Know if you know your workload and start tuning glibc, maybe it can outperform? Not sure but I’d also be skeptical. Tcmalloc and mimalloc both apply really advanced techniques that also require newer kernel support to implement user side RCU iirc. Glibc’s allocator by comparison is much longer in the tooth and just can’t compete on that.

Most workloads don’t care of course, but glibc’s penchant for hanging onto RAM when not needed is one very user visible consequence of this.