On Tue, 17 Jan 2023, Jesper Dangaard Brouer wrote: > When running different network performance microbenchmarks, I started > to notice that performance was reduced (slightly) when machines had > longer uptimes. I believe the cause was 'skbuff_head_cache' got > aliased/merged into the general slub for 256 bytes sized objects (with > my kernel config, without CONFIG_HARDENED_USERCOPY). Well that is a common effect that we see in multiple subsystems. This is due to general memory fragmentation. Depending on the prior load the performance could actually be better after some runtime if the caches are populated avoiding the page allocator etc. The merging could actually be beneficial since there may be more partial slabs to allocate from and thus avoiding expensive calls to the page allocator. I wish we had some effective way of memory defragmentation.
