On 2025-08-20 17:44:01 [+0200], Stefano Brivio wrote: > On Wed, 20 Aug 2025 16:47:37 +0200 > Florian Westphal <fw@xxxxxxxxx> wrote: > > > From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> > > > > The struct nft_pipapo_scratch is allocated, then aligned to the required > > alignment and difference (in bytes) is then saved in align_off. The > > aligned pointer is used later. > > While this works, it gets complicated with all the extra checks if > > all member before map are larger than the required alignment. > > > > Instead of saving the aligned pointer, just save the returned pointer > > and align the map pointer in nft_pipapo_lookup() before using it. The > > alignment later on shouldn't be that expensive. > > The cost of doing the alignment later was the very reason why I added > this whole dance in the first place though. Did you check packet > matching rates before and after this? how? There was something under selftest which I used to ensure it still works. On x86 it should be two additional opcodes (and + lea) and that might be interleaved. Do you remember a rule of thumb of your improvement? As far as I remember the alignment code expects that the "hole" at the begin does not exceed a certain size and the lock there exceeds it. Sebastian
