On Sun, 2014-03-09 at 10:38 -0700, Alexei Starovoitov wrote:
> On Sun, Mar 9, 2014 at 7:45 AM, Eric Dumazet <eric.duma...@gmail.com> wrote:
> > On Sat, 2014-03-08 at 15:15 -0800, Alexei Starovoitov wrote:
> >
> >> +/**
> >> + * sk_run_filter_ext - run an extended filter
> >> + * @ctx: buffer to run the filter on
> >> + * @insn: filter to apply
> >> + *
> >> + * Decode and execute extended BPF instructions.
> >> + * @ctx is the data we are operating on.
> >> + * @filter is the array of filter instructions.
> >> + */
> >> +notrace u32 sk_run_filter_ext(void *ctx, const struct sock_filter_ext
> >> *insn)
> >> +{
> >> + u64 stack[64];
> >> + u64 regs[16];
> >> + void *ptr;
> >> + u64 tmp;
> >> + int off;
>
> First of all, great that you finally reviewed it! Feedback is appreciated :)
>
> > Why is this 'notrace' ?
>
> to avoid overhead of dummy call.
> JITed filters are not adding this dummy call.
> So 'notrace' on interpreter brings it to parity with JITed filters.
Then its a wrong reason.
At the time we wrote JIT, there was (yet) no support for profiling JIT
from perf tools. I asked for help and nobody answered.
Maybe this has changed, if so, please someone add support.
>
> > 80 u64 on the stack, that is 640 bytes to run a filter ????
>
> yes. that was described in commit log and in Doc...filter.txt:
> "
> - 16 4-byte stack slots for register spill-fill replaced with
> up to 512 bytes of multi-use stack space
> "
>
> For interpreter it is prohibitive to dynamically allocate stack space
> that's why it just grabs 64*8 to run any program.
Where is checked the max capacity of this stack ?
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