Do not use rlimit-based memory accounting for bpf local storage maps.
It has been replaced with the memcg-based memory accounting.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-32-guro@fb.com

Do not use rlimit-based memory accounting for xskmap maps.
It has been replaced with the memcg-based memory accounting.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-31-guro@fb.com

Do not use rlimit-based memory accounting for stackmap maps.
It has been replaced with the memcg-based memory accounting.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-30-guro@fb.com

Do not use rlimit-based memory accounting for sockmap and sockhash maps.
It has been replaced with the memcg-based memory accounting.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-29-guro@fb.com

Do not use rlimit-based memory accounting for bpf ringbuffer.
It has been replaced with the memcg-based memory accounting.

bpf_ringbuf_alloc() can't return anything except ERR_PTR(-ENOMEM)
and a valid pointer, so to simplify the code make it return NULL
in the first case. This allows to drop a couple of lines in
ringbuf_map_alloc() and also makes it look similar to other memory
allocating function like kmalloc().
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-28-guro@fb.com

Do not use rlimit-based memory accounting for reuseport_array maps.
It has been replaced with the memcg-based memory accounting.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-27-guro@fb.com

Do not use rlimit-based memory accounting for queue_stack maps.
It has been replaced with the memcg-based memory accounting.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-26-guro@fb.com

Do not use rlimit-based memory accounting for lpm_trie maps.
It has been replaced with the memcg-based memory accounting.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-25-guro@fb.com

Do not use rlimit-based memory accounting for hashtab maps.
It has been replaced with the memcg-based memory accounting.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-24-guro@fb.com

Do not use rlimit-based memory accounting for devmap maps.
It has been replaced with the memcg-based memory accounting.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-23-guro@fb.com

Do not use rlimit-based memory accounting for cgroup storage maps.
It has been replaced with the memcg-based memory accounting.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-22-guro@fb.com

Do not use rlimit-based memory accounting for cpumap maps.
It has been replaced with the memcg-based memory accounting.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-21-guro@fb.com

Do not use rlimit-based memory accounting for bpf_struct_ops maps.
It has been replaced with the memcg-based memory accounting.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-20-guro@fb.com

Do not use rlimit-based memory accounting for arraymap maps.
It has been replaced with the memcg-based memory accounting.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-19-guro@fb.com

Extend xskmap memory accounting to include the memory taken by
the xsk_map_node structure.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-18-guro@fb.com

Include internal metadata into the memcg-based memory accounting.
Also include the memory allocated on updating an element.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-17-guro@fb.com

Account memory used by bpf local storage maps:
per-socket, per-inode and per-task storages.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-16-guro@fb.com

Enable the memcg-based memory accounting for the memory used by
the bpf ringbuffer.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-15-guro@fb.com

Include lpm trie and lpm trie node objects into the memcg-based memory
accounting.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-14-guro@fb.com

Include percpu objects and the size of map metadata into the
accounting.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-13-guro@fb.com

Include map metadata and the node size (struct bpf_dtab_netdev)
into the accounting.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-12-guro@fb.com

Account memory used by cgroup storage maps including metadata
structures.

Account the percpu memory for the percpu flavor of cgroup storage.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-11-guro@fb.com

Include metadata and percpu data into the memcg-based memory
accounting.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-10-guro@fb.com

Include percpu arrays and auxiliary data into the memcg-based memory
accounting.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-9-guro@fb.com

This patch enables memcg-based memory accounting for memory allocated
by __bpf_map_area_alloc(), which is used by many types of bpf maps for
large initial memory allocations.

Please note, that __bpf_map_area_alloc() should not be used outside of
map creation paths without setting the active memory cgroup to the
map's memory cgroup.

Following patches in the series will refine the accounting for
some of the map types.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-8-guro@fb.com

Bpf maps can be updated from an interrupt context and in such
case there is no process which can be charged. It makes the memory
accounting of bpf maps non-trivial.

Fortunately, after commit 4127c650 ("mm: kmem: enable kernel
memcg accounting from interrupt contexts") and commit b87d8cef
("mm, memcg: rework remote charging API to support nesting")
it's finally possible.

To make the ownership model simple and consistent, when the map
is created, the memory cgroup of the current process is recorded.
All subsequent allocations related to the bpf map are charged to
the same memory cgroup. It includes allocations made by any processes
(even if they do belong to a different cgroup) and from interrupts.

This commit introduces 3 new helpers, which will be used by following
commits to enable the accounting of bpf maps memory:
  - bpf_map_kmalloc_node()
  - bpf_map_kzalloc()
  - bpf_map_alloc_percpu()

They are wrapping popular memory allocation functions. They set
the active memory cgroup to the map's memory cgroup and add
__GFP_ACCOUNT to the passed gfp flags. Then they call into
the corresponding memory allocation function and restore
the original active memory cgroup.

These helpers are supposed to use everywhere except the map creation
path. During the map creation when the map structure is allocated by
itself, it cannot be passed to those helpers. In those cases default
memory allocation function will be used with the __GFP_ACCOUNT flag.
Signed-off-by: Roman Gushchin <guro@fb.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-7-guro@fb.com

Include memory used by bpf programs into the memcg-based accounting.
This includes the memory used by programs itself, auxiliary data,
statistics and bpf line info. A memory cgroup containing the
process which loads the program is getting charged.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20201201215900.3569844-6-guro@fb.com

PageKmemcg flag is currently defined as a page type (like buddy, offline,
table and guard).  Semantically it means that the page was accounted as a
kernel memory by the page allocator and has to be uncharged on the
release.

As a side effect of defining the flag as a page type, the accounted page
can't be mapped to userspace (look at page_has_type() and comments above).
In particular, this blocks the accounting of vmalloc-backed memory used
by some bpf maps, because these maps do map the memory to userspace.

One option is to fix it by complicating the access to page->mapcount,
which provides some free bits for page->page_type.

But it's way better to move this flag into page->memcg_data flags.
Indeed, the flag makes no sense without enabled memory cgroups and memory
cgroup pointer set in particular.

This commit replaces PageKmemcg() and __SetPageKmemcg() with
PageMemcgKmem() and an open-coded OR operation setting the memcg pointer
with the MEMCG_DATA_KMEM bit.  __ClearPageKmemcg() can be simple deleted,
as the whole memcg_data is zeroed at once.

As a bonus, on !CONFIG_MEMCG build the PageMemcgKmem() check will be
compiled out.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Link: https://lkml.kernel.org/r/20201027001657.3398190-5-guro@fb.com
Link: https://lore.kernel.org/bpf/20201201215900.3569844-5-guro@fb.com

The lowest bit in page->memcg_data is used to distinguish between struct
memory_cgroup pointer and a pointer to a objcgs array.  All checks and
modifications of this bit are open-coded.

Let's formalize it using page memcg flags, defined in enum
page_memcg_data_flags.

Additional flags might be added later.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Link: https://lkml.kernel.org/r/20201027001657.3398190-4-guro@fb.com
Link: https://lore.kernel.org/bpf/20201201215900.3569844-4-guro@fb.com

To gather all direct accesses to struct page's memcg_data field in one
place, let's introduce 3 new helpers to use in the slab accounting code:

  struct obj_cgroup **page_objcgs(struct page *page);
  struct obj_cgroup **page_objcgs_check(struct page *page);
  bool set_page_objcgs(struct page *page, struct obj_cgroup **objcgs);

They are similar to the corresponding API for generic pages, except that
the setter can return false, indicating that the value has been already
set from a different thread.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lkml.kernel.org/r/20201027001657.3398190-3-guro@fb.com
Link: https://lore.kernel.org/bpf/20201201215900.3569844-3-guro@fb.com

Patch series "mm: allow mapping accounted kernel pages to userspace", v6.

Currently a non-slab kernel page which has been charged to a memory cgroup
can't be mapped to userspace.  The underlying reason is simple: PageKmemcg
flag is defined as a page type (like buddy, offline, etc), so it takes a
bit from a page->mapped counter.  Pages with a type set can't be mapped to
userspace.

But in general the kmemcg flag has nothing to do with mapping to
userspace.  It only means that the page has been accounted by the page
allocator, so it has to be properly uncharged on release.

Some bpf maps are mapping the vmalloc-based memory to userspace, and their
memory can't be accounted because of this implementation detail.

This patchset removes this limitation by moving the PageKmemcg flag into
one of the free bits of the page->mem_cgroup pointer.  Also it formalizes
accesses to the page->mem_cgroup and page->obj_cgroups using new helpers,
adds several checks and removes a couple of obsolete functions.  As the
result the code became more robust with fewer open-coded bit tricks.

This patch (of 4):

Currently there are many open-coded reads of the page->mem_cgroup pointer,
as well as a couple of read helpers, which are barely used.

It creates an obstacle on a way to reuse some bits of the pointer for
storing additional bits of information.  In fact, we already do this for
slab pages, where the last bit indicates that a pointer has an attached
vector of objcg pointers instead of a regular memcg pointer.

This commits uses 2 existing helpers and introduces a new helper to
converts all read sides to calls of these helpers:
  struct mem_cgroup *page_memcg(struct page *page);
  struct mem_cgroup *page_memcg_rcu(struct page *page);
  struct mem_cgroup *page_memcg_check(struct page *page);

page_memcg_check() is intended to be used in cases when the page can be a
slab page and have a memcg pointer pointing at objcg vector.  It does
check the lowest bit, and if set, returns NULL.  page_memcg() contains a
VM_BUG_ON_PAGE() check for the page not being a slab page.

To make sure nobody uses a direct access, struct page's
mem_cgroup/obj_cgroups is converted to unsigned long memcg_data.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Link: https://lkml.kernel.org/r/20201027001657.3398190-1-guro@fb.com
Link: https://lkml.kernel.org/r/20201027001657.3398190-2-guro@fb.com
Link: https://lore.kernel.org/bpf/20201201215900.3569844-2-guro@fb.com

Stanislav Fomichev says:

====================

This might be useful for the listener sockets to pre-populate
some options. Since those helpers require locked sockets,
I'm changing bind hooks to lock/unlock the sockets. This
should not cause any performance overhead because at this
point there shouldn't be any socket lock contention and the
locking/unlocking should be cheap.

Also, as part of the series, I convert test_sock_addr bpf
assembly into C (and preserve the narrow load tests) to
make it easier to extend with th bpf_setsockopt later on.

v2:
* remove version from bpf programs (Andrii Nakryiko)
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

To make sure it doesn't trigger sock_owned_by_me splat.
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20201202172516.3483656-4-sdf@google.com

I have to now lock/unlock socket for the bind hook execution.
That shouldn't cause any overhead because the socket is unbound
and shouldn't receive any traffic.
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrey Ignatov <rdna@fb.com>
Link: https://lore.kernel.org/bpf/20201202172516.3483656-3-sdf@google.com

I'm planning to extend it in the next patches. It's much easier to
work with C than BPF assembly.
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20201202172516.3483656-2-sdf@google.com

Stephen reported the following build error for !CONFIG_NET_RX_BUSY_POLL
built kernels:

  In file included from fs/select.c:32:
  include/net/busy_poll.h: In function 'sk_mark_napi_id_once':
  include/net/busy_poll.h:150:36: error: 'const struct sk_buff' has no member named 'napi_id'
    150 |  __sk_mark_napi_id_once_xdp(sk, skb->napi_id);
        |                                    ^~

Fix it by wrapping a CONFIG_NET_RX_BUSY_POLL around the helpers.

Fixes: b02e5a0e ("xsk: Propagate napi_id to XDP socket Rx path")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Björn Töpel <bjorn.topel@intel.com>
Link: https://lore.kernel.org/linux-next/20201201190746.7d3357fb@canb.auug.org.au

Björn Töpel says:

====================
This series introduces three new features:

1. A new "heavy traffic" busy-polling variant that works in concert
   with the existing napi_defer_hard_irqs and gro_flush_timeout knobs.

2. A new socket option that let a user change the busy-polling NAPI
   budget.

3. Allow busy-polling to be performed on XDP sockets.

The existing busy-polling mode, enabled by the SO_BUSY_POLL socket
option or system-wide using the /proc/sys/net/core/busy_read knob, is
an opportunistic. That means that if the NAPI context is not
scheduled, it will poll it. If, after busy-polling, the budget is
exceeded the busy-polling logic will schedule the NAPI onto the
regular softirq handling.

One implication of the behavior above is that a busy/heavy loaded NAPI
context will never enter/allow for busy-polling. Some applications
prefer that most NAPI processing would be done by busy-polling.

This series adds a new socket option, SO_PREFER_BUSY_POLL, that works
in concert with the napi_defer_hard_irqs and gro_flush_timeout
knobs. The napi_defer_hard_irqs and gro_flush_timeout knobs were
introduced in commit 6f8b12d6 ("net: napi: add hard irqs deferral
feature"), and allows for a user to defer interrupts to be enabled and
instead schedule the NAPI context from a watchdog timer. When a user
enables the SO_PREFER_BUSY_POLL, again with the other knobs enabled,
and the NAPI context is being processed by a softirq, the softirq NAPI
processing will exit early to allow the busy-polling to be performed.

If the application stops performing busy-polling via a system call,
the watchdog timer defined by gro_flush_timeout will timeout, and
regular softirq handling will resume.

In summary; Heavy traffic applications that prefer busy-polling over
softirq processing should use this option.

Patch 6 touches a lot of drivers, so the Cc: list is grossly long.

Example usage:

  $ echo 2 | sudo tee /sys/class/net/ens785f1/napi_defer_hard_irqs
  $ echo 200000 | sudo tee /sys/class/net/ens785f1/gro_flush_timeout

Note that the timeout should be larger than the userspace processing
window, otherwise the watchdog will timeout and fall back to regular
softirq processing.

Enable the SO_BUSY_POLL/SO_PREFER_BUSY_POLL options on your socket.

Performance simple UDP ping-pong:

A packet generator blasts UDP packets from a packet generator to a
certain {src,dst}IP/port, so a dedicated ksoftirq will be busy
handling the packets at a certain core.

A simple UDP test program that simply does recvfrom/sendto is running
at the host end. Throughput in pps and RTT latency is measured at the
packet generator.

/proc/sys/net/core/busy_read is set (20).

Min       Max       Avg (usec)

1. Blocking 2-cores:                       490Kpps
 1218.192  1335.427  1271.083

2. Blocking, 1-core:                       155Kpps
 1327.195 17294.855  4761.367

3. Non-blocking, 2-cores:                  475Kpps
 1221.197  1330.465  1270.740

4. Non-blocking, 1-core:                     3Kpps
29006.482 37260.465 33128.367

5. Non-blocking, prefer busy-poll, 1-core: 420Kpps
 1202.535  5494.052  4885.443

Scenario 2 and 5 shows when the new option should be used. Throughput
go from 155 to 420Kpps, average latency are similar, but the tail
latencies are much better for the latter.

Performance XDP sockets:

Again, a packet generator blasts UDP packets from a packet generator
to a certain {src,dst}IP/port.

Today, running XDP sockets sample on the same core as the softirq
handling, performance tanks mainly because we do not yield to
user-space when the XDP socket Rx queue is full.

  # taskset -c 5 ./xdpsock -i ens785f1 -q 5 -n 1 -r
  Rx: 64Kpps

  # # preferred busy-polling, budget 8
  # taskset -c 5 ./xdpsock -i ens785f1 -q 5 -n 1 -r -B -b 8
  Rx 9.9Mpps
  # # preferred busy-polling, budget 64
  # taskset -c 5 ./xdpsock -i ens785f1 -q 5 -n 1 -r -B -b 64
  Rx: 19.3Mpps
  # # preferred busy-polling, budget 256
  # taskset -c 5 ./xdpsock -i ens785f1 -q 5 -n 1 -r -B -b 256
  Rx: 21.4Mpps
  # # preferred busy-polling, budget 512
  # taskset -c 5 ./xdpsock -i ens785f1 -q 5 -n 1 -r -B -b 512
  Rx: 21.7Mpps

Compared to the two-core case:
  # taskset -c 4 ./xdpsock -i ens785f1 -q 20 -n 1 -r
  Rx: 20.7Mpps

We're getting better single-core performance than two, for this naïve
drop scenario.

Performance netperf UDP_RR:

Note that netperf UDP_RR is not a heavy traffic tests, and preferred
busy-polling is not typically something we want to use here.

  $ echo 20 | sudo tee /proc/sys/net/core/busy_read
  $ netperf -H 192.168.1.1 -l 30 -t UDP_RR -v 2 -- \
      -o min_latency,mean_latency,max_latency,stddev_latency,transaction_rate

busy-polling blocking sockets:            12,13.33,224,0.63,74731.177

I hacked netperf to use non-blocking sockets and re-ran:

busy-polling non-blocking sockets:        12,13.46,218,0.72,73991.172
prefer busy-polling non-blocking sockets: 12,13.62,221,0.59,73138.448

Using the preferred busy-polling mode does not impact performance.

The above tests was done for the 'ice' driver.

Thanks to Jakub for suggesting this busy-polling addition [1], and
Eric for all input/review!

Changes:

rfc-v1 [2] -> rfc-v2:
  * Changed name from bias to prefer.
  * Base the work on Eric's/Luigi's defer irq/gro timeout work.
  * Proper GRO flushing.
  * Build issues for some XDP drivers.

rfc-v2 [3] -> v1:
  * Fixed broken qlogic build.
  * Do not trigger an IPI (XDP socket wakeup) when busy-polling is
    enabled.

v1 [4] -> v2:
  * Added napi_id to socionext driver, and added Ilias Acked-by:. (Ilias)
  * Added a samples patch to improve busy-polling for xdpsock/l2fwd.
  * Correctly mark atomic operations with {WRITE,READ}_ONCE, to make
    KCSAN and the code readers happy. (Eric)
  * Check NAPI budget not to exceed U16_MAX. (Eric)
  * Added kdoc.

v2 [5] -> v3:
  * Collected Acked-by.
  * Check NAPI disable prior prefer busy-polling. (Jakub)
  * Added napi_id registration for virtio-net. (Michael)
  * Added napi_id registration for veth.

v3 [6] -> v4:
  * Collected Acked-by/Reviewed-by.

[1] https://lore.kernel.org/netdev/20200925120652.10b8d7c5@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com/
[2] https://lore.kernel.org/bpf/20201028133437.212503-1-bjorn.topel@gmail.com/
[3] https://lore.kernel.org/bpf/20201105102812.152836-1-bjorn.topel@gmail.com/
[4] https://lore.kernel.org/bpf/20201112114041.131998-1-bjorn.topel@gmail.com/
[5] https://lore.kernel.org/bpf/20201116110416.10719-1-bjorn.topel@gmail.com/
[6] https://lore.kernel.org/bpf/20201119083024.119566-1-bjorn.topel@gmail.com/
====================
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Support for the SO_BUSY_POLL_BUDGET setsockopt, via the batching
option ('b').
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Magnus Karlsson <magnus.karlsson@intel.com>
Link: https://lore.kernel.org/bpf/20201130185205.196029-11-bjorn.topel@gmail.com

Add a new option to xdpsock, 'B', for busy-polling. This option will
also set the batching size, 'b' option, to the busy-poll budget.
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Magnus Karlsson <magnus.karlsson@intel.com>
Link: https://lore.kernel.org/bpf/20201130185205.196029-10-bjorn.topel@gmail.com

Start using recvfrom() the l2fwd scenario, instead of poll() which is
more expensive and need additional knobs for busy-polling.
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Magnus Karlsson <magnus.karlsson@intel.com>
Link: https://lore.kernel.org/bpf/20201130185205.196029-9-bjorn.topel@gmail.com