> On Sep 10, 2021, at 11:40 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> 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. Yep, some JIT magic could save one entry here. > >> 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. To inline migrate_disable, we may need expose this_rq() in include/, or use some other alternatives. I am planning to optimize that after this set gets in. Thanks, Song > >> ID: 6 from bpf_testmod_loop_test+20 to __bpf_prog_enter+0 > > And this is the first branch out of the test program, giving 7 entries > now, of which we can remove at least 2 more with a bit of elbow greace, > right? > >> ID: 7 from bpf_testmod_loop_test+20 to bpf_testmod_loop_test+13 >> ID: 8 from bpf_testmod_loop_test+20 to bpf_testmod_loop_test+13 >> >> I will fold this in and send v7. > > Excellent.
