On Mon, Jun 20, 2022 at 07:11:45PM +0800, Aaron Lu wrote: > Hi Song, > > On Fri, May 20, 2022 at 04:57:50PM -0700, Song Liu wrote: > > ... ... > > > The primary goal of bpf_prog_pack is to reduce iTLB miss rate and reduce > > direct memory mapping fragmentation. This leads to non-trivial performance > > improvements. > > > > For our web service production benchmark, bpf_prog_pack on 4kB pages > > gives 0.5% to 0.7% more throughput than not using bpf_prog_pack. > > bpf_prog_pack on 2MB pages 0.6% to 0.9% more throughput than not using > > bpf_prog_pack. Note that 0.5% is a huge improvement for our fleet. I > > believe this is also significant for other companies with many thousand > > servers. > > > > I'm evaluationg performance impact due to direct memory mapping > fragmentation BTW how exactly are you doing this? Luis > and seeing the above, I wonder: is the performance improve > mostly due to prog pack and hugepage instead of less direct mapping > fragmentation? > > I can understand that when progs are packed together, iTLB miss rate will > be reduced and thus, performance can be improved. But I don't see > immediately how direct mapping fragmentation can impact performance since > the bpf code are running from the module alias addresses, not the direct > mapping addresses IIUC? > > I appreciate it if you can shed some light on performance impact direct > mapping fragmentation can cause, thanks.
