I have a ~1.7G file with just under 620k events (not exactly big by our standards), and parsing speed (with -N to disable plugins) goes from ~4.5 seconds on commit 1ad32c24746 to >>4.5 minutes (I aborted there) on master. I was talking to Steven about another issue, and he pointed me to commit c2fc2bc296f7. Reverting that on master makes it take ~2 seconds, so that'd actually be an improvement.
Proposed solution: revert the behaviour for this use case, as it was before commit c2fc2bc296f7 https://patchwork.kernel.org/patch/11003953/
Fixed by commit 0bdae7b3fbcd ("trace-cmd: Do not free pages from the lookup table in struct cpu_data in case trace file is loaded.").