bpf.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: "Toke Høiland-Jørgensen" <toke@redhat.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>,
	Alexei Starovoitov <ast@kernel.org>,
	Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
	Yonghong Song <yhs@fb.com>,
	Marek Majkowski <marek@cloudflare.com>,
	Lorenz Bauer <lmb@cloudflare.com>,
	Alan Maguire <alan.maguire@oracle.com>,
	Jesper Dangaard Brouer <brouer@redhat.com>,
	David Miller <davem@davemloft.net>,
	netdev@vger.kernel.org, bpf@vger.kernel.org
Subject: Re: [PATCH bpf-next v3 1/5] bpf: Support chain calling multiple BPF programs after each other
Date: Tue, 8 Oct 2019 18:51:19 -0700	[thread overview]
Message-ID: <20191009015117.pldowv6n3k5p3ghr@ast-mbp.dhcp.thefacebook.com> (raw)
In-Reply-To: <87sgo3lkx9.fsf@toke.dk>

On Tue, Oct 08, 2019 at 10:07:46AM +0200, Toke Høiland-Jørgensen wrote:
> Alexei Starovoitov <alexei.starovoitov@gmail.com> writes:
> 
> > On Mon, Oct 07, 2019 at 07:20:36PM +0200, Toke Høiland-Jørgensen wrote:
> >> From: Toke Høiland-Jørgensen <toke@redhat.com>
> >> 
> >> This adds support for wrapping eBPF program dispatch in chain calling
> >> logic. The code injection is controlled by a flag at program load time; if
> >> the flag is set, the BPF program will carry a flag bit that changes the
> >> program dispatch logic to wrap it in a chain call loop.
> >> 
> >> Ideally, it shouldn't be necessary to set the flag on program load time,
> >> but rather inject the calls when a chain call program is first loaded. The
> >> allocation logic sets the whole of struct bpf_prog to be read-only memory,
> >> so it can't immediately be modified, but conceivably we could just unlock
> >> the first page of the struct and flip the bit when a chain call program is
> >> first attached.
> >> 
> >> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
> >> ---
> >>  include/linux/bpf.h      |    3 +++
> >>  include/linux/filter.h   |   34 ++++++++++++++++++++++++++++++++--
> >>  include/uapi/linux/bpf.h |    6 ++++++
> >>  kernel/bpf/core.c        |    6 ++++++
> >>  kernel/bpf/syscall.c     |    4 +++-
> >>  5 files changed, 50 insertions(+), 3 deletions(-)
> >> 
> >> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> >> index 5b9d22338606..13e5f38cf5c6 100644
> >> --- a/include/linux/bpf.h
> >> +++ b/include/linux/bpf.h
> >> @@ -365,6 +365,8 @@ struct bpf_prog_stats {
> >>  	struct u64_stats_sync syncp;
> >>  };
> >>  
> >> +#define BPF_NUM_CHAIN_SLOTS 8
> >> +
> >>  struct bpf_prog_aux {
> >>  	atomic_t refcnt;
> >>  	u32 used_map_cnt;
> >> @@ -383,6 +385,7 @@ struct bpf_prog_aux {
> >>  	struct list_head ksym_lnode;
> >>  	const struct bpf_prog_ops *ops;
> >>  	struct bpf_map **used_maps;
> >> +	struct bpf_prog *chain_progs[BPF_NUM_CHAIN_SLOTS];
> >>  	struct bpf_prog *prog;
> >>  	struct user_struct *user;
> >>  	u64 load_time; /* ns since boottime */
> >> diff --git a/include/linux/filter.h b/include/linux/filter.h
> >> index 2ce57645f3cd..3d1e4991e61d 100644
> >> --- a/include/linux/filter.h
> >> +++ b/include/linux/filter.h
> >> @@ -21,6 +21,7 @@
> >>  #include <linux/kallsyms.h>
> >>  #include <linux/if_vlan.h>
> >>  #include <linux/vmalloc.h>
> >> +#include <linux/nospec.h>
> >>  
> >>  #include <net/sch_generic.h>
> >>  
> >> @@ -528,6 +529,7 @@ struct bpf_prog {
> >>  				is_func:1,	/* program is a bpf function */
> >>  				kprobe_override:1, /* Do we override a kprobe? */
> >>  				has_callchain_buf:1, /* callchain buffer allocated? */
> >> +				chain_calls:1, /* should this use the chain_call wrapper */
> >>  				enforce_expected_attach_type:1; /* Enforce expected_attach_type checking at attach time */
> >>  	enum bpf_prog_type	type;		/* Type of BPF program */
> >>  	enum bpf_attach_type	expected_attach_type; /* For some prog types */
> >> @@ -551,6 +553,30 @@ struct sk_filter {
> >>  	struct bpf_prog	*prog;
> >>  };
> >>  
> >> +#define BPF_MAX_CHAIN_CALLS 32
> >> +static __always_inline unsigned int do_chain_calls(const struct bpf_prog *prog,
> >> +						   const void *ctx)
> >> +{
> >> +	int i = BPF_MAX_CHAIN_CALLS;
> >> +	int idx;
> >> +	u32 ret;
> >> +
> >> +	do {
> >> +		ret = (*(prog)->bpf_func)(ctx, prog->insnsi);
> >
> > This breaks program stats.
> 
> Oh, right, silly me. Will fix.
> 
> >> +
> >> +		if (ret + 1 >= BPF_NUM_CHAIN_SLOTS) {
> >> +			prog = prog->aux->chain_progs[0];
> >> +			continue;
> >> +		}
> >> +		idx = ret + 1;
> >> +		idx = array_index_nospec(idx, BPF_NUM_CHAIN_SLOTS);
> >> +
> >> +		prog = prog->aux->chain_progs[idx] ?: prog->aux->chain_progs[0];
> >> +	} while (prog && --i);
> >> +
> >> +	return ret;
> >> +}
> >> +
> >>  DECLARE_STATIC_KEY_FALSE(bpf_stats_enabled_key);
> >>  
> >>  #define BPF_PROG_RUN(prog, ctx)	({				\
> >> @@ -559,14 +585,18 @@ DECLARE_STATIC_KEY_FALSE(bpf_stats_enabled_key);
> >>  	if (static_branch_unlikely(&bpf_stats_enabled_key)) {	\
> >>  		struct bpf_prog_stats *stats;			\
> >>  		u64 start = sched_clock();			\
> >> -		ret = (*(prog)->bpf_func)(ctx, (prog)->insnsi);	\
> >> +		ret = prog->chain_calls ?			\
> >> +			do_chain_calls(prog, ctx) :			\
> >> +			 (*(prog)->bpf_func)(ctx, (prog)->insnsi);	\
> >
> > I thought you agreed on 'no performance regressions' rule?
> 
> As I wrote in the cover letter I could not measurable a performance
> impact from this, even with the simplest possible XDP program (where
> program setup time has the largest impact).
> 
> This was the performance before/after patch (also in the cover letter):
> 
> Before patch (XDP DROP program):  31.5 Mpps
> After patch (XDP DROP program):   32.0 Mpps
> 
> So actually this *increases* performance ;)
> (Or rather, the difference is within the measurement uncertainty on my
> system).

I have hard time believing such numbers.
If I wasn't clear before: Nack to such hack in BPF_PROG_RUN.
Please implement proper indirect calls and jumps.
Apps have to cooperate with each other regardless
whereas above is a narrow solution to one problem.


  reply	other threads:[~2019-10-09  1:51 UTC|newest]

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-07 17:20 [PATCH bpf-next v3 0/5] xdp: Support multiple programs on a single interface through chain calls Toke Høiland-Jørgensen
2019-10-07 17:20 ` [PATCH bpf-next v3 1/5] bpf: Support chain calling multiple BPF programs after each other Toke Høiland-Jørgensen
2019-10-07 20:42   ` Alexei Starovoitov
2019-10-08  8:07     ` Toke Høiland-Jørgensen
2019-10-09  1:51       ` Alexei Starovoitov [this message]
2019-10-09  8:03         ` Toke Høiland-Jørgensen
2019-10-10  4:41           ` Alexei Starovoitov
2019-10-14 12:35             ` Toke Høiland-Jørgensen
2019-10-14 17:08               ` John Fastabend
2019-10-14 18:48                 ` Toke Høiland-Jørgensen
2019-10-15 16:30                   ` Edward Cree
2019-10-15 16:42                     ` Toke Høiland-Jørgensen
2019-10-15 18:33                       ` Edward Cree
2019-10-17 12:11                         ` Toke Høiland-Jørgensen
2019-10-22 17:27                           ` Edward Cree
2019-10-22 18:07                             ` Toke Høiland-Jørgensen
2019-11-12  2:51                               ` static and dynamic linking. Was: [PATCH bpf-next v3 1/5] bpf: Support chain calling multiple BPF Alexei Starovoitov
2019-11-12 16:20                                 ` Toke Høiland-Jørgensen
2019-11-12 19:52                                   ` Alexei Starovoitov
2019-11-12 21:25                                     ` Edward Cree
2019-11-12 23:18                                       ` Alexei Starovoitov
2019-11-13 18:30                                         ` Edward Cree
2019-11-13 18:51                                           ` Andrii Nakryiko
2019-11-15  2:13                                           ` Alexei Starovoitov
2019-11-15 16:56                                             ` John Fastabend
2019-11-12 23:25                                     ` John Fastabend
2019-11-13  0:21                                       ` Alexei Starovoitov
2019-11-13  5:33                                         ` John Fastabend
2019-11-15  1:50                                           ` Alexei Starovoitov
2019-11-15 16:39                                             ` John Fastabend
2019-11-14 15:41                                     ` Toke Høiland-Jørgensen
2019-11-12 16:32                                 ` Edward Cree
2019-11-15 11:48                                 ` Lorenz Bauer
2019-11-15 23:02                                   ` Alexei Starovoitov
2019-11-18 13:29                                     ` Lorenz Bauer
2019-10-21 23:51                         ` [PATCH bpf-next v3 1/5] bpf: Support chain calling multiple BPF programs after each other Edward Cree
2019-10-16  2:28               ` Alexei Starovoitov
2019-10-16  8:27                 ` Jesper Dangaard Brouer
2019-10-16 10:35                   ` Daniel Borkmann
2019-10-16 11:16                     ` Toke Høiland-Jørgensen
2019-10-16 13:51                 ` Toke Høiland-Jørgensen
2019-10-19 20:09                   ` bpf indirect calls Alexei Starovoitov
2019-10-20 10:58                     ` Toke Høiland-Jørgensen
2019-10-25 16:30                       ` Alexei Starovoitov
2019-10-27 12:15                         ` Toke Høiland-Jørgensen
2019-10-09 10:19         ` [PATCH bpf-next v3 1/5] bpf: Support chain calling multiple BPF programs after each other Jesper Dangaard Brouer
2019-10-09 17:57           ` Alexei Starovoitov
2019-10-07 17:20 ` [PATCH bpf-next v3 2/5] bpf: Add support for setting chain call sequence for programs Toke Høiland-Jørgensen
2019-10-07 20:38   ` Daniel Borkmann
2019-10-08  8:09     ` Toke Høiland-Jørgensen
2019-10-07 17:20 ` [PATCH bpf-next v3 3/5] tools: Update bpf.h header for program chain calls Toke Høiland-Jørgensen
2019-10-07 17:20 ` [PATCH bpf-next v3 4/5] libbpf: Add syscall wrappers for BPF_PROG_CHAIN_* commands Toke Høiland-Jørgensen
2019-10-07 17:20 ` [PATCH bpf-next v3 5/5] selftests: Add tests for XDP chain calls Toke Høiland-Jørgensen
2019-10-07 18:58 ` [PATCH bpf-next v3 0/5] xdp: Support multiple programs on a single interface through " John Fastabend
2019-10-08  8:42   ` Toke Høiland-Jørgensen

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20191009015117.pldowv6n3k5p3ghr@ast-mbp.dhcp.thefacebook.com \
    --to=alexei.starovoitov@gmail.com \
    --cc=alan.maguire@oracle.com \
    --cc=ast@kernel.org \
    --cc=bpf@vger.kernel.org \
    --cc=brouer@redhat.com \
    --cc=daniel@iogearbox.net \
    --cc=davem@davemloft.net \
    --cc=kafai@fb.com \
    --cc=lmb@cloudflare.com \
    --cc=marek@cloudflare.com \
    --cc=netdev@vger.kernel.org \
    --cc=songliubraving@fb.com \
    --cc=toke@redhat.com \
    --cc=yhs@fb.com \
    --subject='Re: [PATCH bpf-next v3 1/5] bpf: Support chain calling multiple BPF programs after each other' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).