I recently had some trouble figuring out where exactly a program was consing, so I wrote a quick hack for converting the SBCL statistical CPU profiler to an allocation profiler (patch against Instead of getting profiler ticks from the system itimer, the allocator will trigger a tick every time it opens a new allocation region (basically whenever 8kB have been allocated). To use SB-SPROF in allocation profiling mode, just pass :ALLOC T to WITH-PROFILING / START-PROFILING. Other than that, all SB-SPROF functionality should work normally (disassembler integration, call graphs, slime-sprof, etc).

For example the following slime-sprof screenshot (click on thumbnail for a larger image) shows that around 7% of the consing during a profiling run was in SB-C:MAKE-TN or functions called from it, 0.91% was in APPEND when called from SB-KERNEL:VALUES-TYPE-TYPES, etc.

The patch isn't really committable as such. Since the functionality is not needed very often, I probably won't bother cleaning it up. But it might still be useful to someone even in this crude state, hence this post.