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xdp: split code for map vs non-map redirect 

The compiler does an efficient job of inlining static C functions.
Perf top clearly shows that almost everything gets inlined into the
function call xdp_do_redirect.

The function xdp_do_redirect end-up containing and interleaving the
map and non-map redirect code.  This is sub-optimal, as it would be
strange for an XDP program to use both types of redirect in the same
program. The two use-cases are separate, and interleaving the code
just cause more instruction-cache pressure.

I would like to stress (again) that the non-map variant bpf_redirect
is very slow compared to the bpf_redirect_map variant, approx half the
speed.  Measured with driver i40e the difference is:

- map     redirect: 13,250,350 pps
- non-map redirect:  7,491,425 pps

For this reason, the function name of the non-map variant of redirect
have been called xdp_do_redirect_slow.  This hopefully gives a hint
when using perf, that this is not the optimal XDP redirect operating mode.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Jesper Dangaard Brouer 2018-09-03 09:55:07 +02:00 committed by Alexei Starovoitov
parent 2a68d85fe1
commit 47b123ed9e
1 changed files with 30 additions and 22 deletions
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52
net/core/filter.c
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@ -3175,6 +3175,32 @@ static int __bpf_tx_xdp(struct net_device *dev,
return 0;
}
static noinline int
xdp_do_redirect_slow(struct net_device *dev, struct xdp_buff *xdp,
struct bpf_prog *xdp_prog, struct bpf_redirect_info *ri)
{
struct net_device *fwd;
u32 index = ri->ifindex;
int err;
fwd = dev_get_by_index_rcu(dev_net(dev), index);
ri->ifindex = 0;
if (unlikely(!fwd)) {
err = -EINVAL;
goto err;
}
err = __bpf_tx_xdp(fwd, NULL, xdp, 0);
if (unlikely(err))
goto err;
_trace_xdp_redirect(dev, xdp_prog, index);
return 0;
err:
_trace_xdp_redirect_err(dev, xdp_prog, index, err);
return err;
}
static int __bpf_tx_xdp_map(struct net_device *dev_rx, void *fwd,
struct bpf_map *map,
struct xdp_buff *xdp,
@ -3269,9 +3295,9 @@ void bpf_clear_redirect_map(struct bpf_map *map)
}
static int xdp_do_redirect_map(struct net_device *dev, struct xdp_buff *xdp,
struct bpf_prog *xdp_prog, struct bpf_map *map)
struct bpf_prog *xdp_prog, struct bpf_map *map,
struct bpf_redirect_info *ri)
{
struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
u32 index = ri->ifindex;
void *fwd = NULL;
int err;
@ -3304,29 +3330,11 @@ int xdp_do_redirect(struct net_device *dev, struct xdp_buff *xdp,
{
struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
struct bpf_map *map = READ_ONCE(ri->map);
struct net_device *fwd;
u32 index = ri->ifindex;
int err;
if (likely(map))
return xdp_do_redirect_map(dev, xdp, xdp_prog, map);
return xdp_do_redirect_map(dev, xdp, xdp_prog, map, ri);
fwd = dev_get_by_index_rcu(dev_net(dev), index);
ri->ifindex = 0;
if (unlikely(!fwd)) {
err = -EINVAL;
goto err;
}
err = __bpf_tx_xdp(fwd, NULL, xdp, 0);
if (unlikely(err))
goto err;
_trace_xdp_redirect(dev, xdp_prog, index);
return 0;
err:
_trace_xdp_redirect_err(dev, xdp_prog, index, err);
return err;
return xdp_do_redirect_slow(dev, xdp, xdp_prog, ri);
}
EXPORT_SYMBOL_GPL(xdp_do_redirect);