On Thu, 15 Feb 2024 18:51:41 -0500 Kent Overstreet <kent.overstreet@xxxxxxxxx> wrote: > Most of that is data (505024), not text (68582, or 66k). > And the 4K extra would have been data too. > The data is mostly the alloc tags themselves (one per allocation > callsite, and you compiled the entire kernel), so that's expected. > > Of the text, a lot of that is going to be slowpath stuff - module load > and unload hooks, formatt and printing the output, other assorted bits. > > Then there's Allocation and deallocating obj extensions vectors - not > slowpath but not super fast path, not every allocation. > > The fastpath instruction count overhead is pretty small > - actually doing the accounting - the core of slub.c, page_alloc.c, > percpu.c > - setting/restoring the alloc tag: this is overhead we add to every > allocation callsite, so it's the most relevant - but it's just a few > instructions. > > So that's the breakdown. Definitely not zero overhead, but that fixed > memory overhead (and additionally, the percpu counters) is the price we > pay for very low runtime CPU overhead. But where are the benchmarks that are not micro-benchmarks. How much overhead does this cause to those? Is it in the noise, or is it noticeable? -- Steve
