On Fri, Sep 10, 2021 at 08:40:27PM +0200, Peter Zijlstra wrote: > On Fri, Sep 10, 2021 at 06:27:36PM +0000, Song Liu wrote: > > > This works great and saves 3 entries! We have the following now: > > Yay! > > > ID: 0 from bpf_get_branch_snapshot+18 to intel_pmu_snapshot_branch_stack+0 > > is unavoidable, we need to end up in intel_pmu_snapshot_branch_stack() > eventually. > > > ID: 1 from __brk_limit+477143934 to bpf_get_branch_snapshot+0 > > could be elided by having the JIT emit the call to > intel_pmu_snapshot_branch_stack directly, instead of laundering it > through that helper I suppose. > > > ID: 2 from __brk_limit+477192263 to __brk_limit+477143880 # trampoline > > ID: 3 from __bpf_prog_enter+34 to __brk_limit+477192251 > > -ENOCLUE > > > ID: 4 from migrate_disable+60 to __bpf_prog_enter+9 > > ID: 5 from __bpf_prog_enter+4 to migrate_disable+0 > > I suppose we can reduce that to a single branch if we inline > migrate_disable() here, that thing unfortunately needs one branch > itself. Oooh, since we put local_irq_save/restore() in intel_pmu_snapshot_branch_stack(), we no longer need to be after migrate_disable(). You could go back to placing it earlier!
