A couple of minor bugfixes.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost
Pull virtio bugfixes from Michael Tsirkin:
"A couple of minor bugfixes"
* tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost:
virtio_net: fix return value check in receive_mergeable()
virtio_mmio: add cleanup for virtio_mmio_remove
virtio_mmio: add cleanup for virtio_mmio_probe
The function virtqueue_get_buf_ctx() could return NULL, the return
value 'buf' need to be checked with NULL, not value 'ctx'.
Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Merge updates from Andrew Morton:
- a few misc bits
- ocfs2 updates
- almost all of MM
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (131 commits)
memory hotplug: fix comments when adding section
mm: make alloc_node_mem_map a void call if we don't have CONFIG_FLAT_NODE_MEM_MAP
mm: simplify nodemask printing
mm,oom_reaper: remove pointless kthread_run() error check
mm/page_ext.c: check if page_ext is not prepared
writeback: remove unused function parameter
mm: do not rely on preempt_count in print_vma_addr
mm, sparse: do not swamp log with huge vmemmap allocation failures
mm/hmm: remove redundant variable align_end
mm/list_lru.c: mark expected switch fall-through
mm/shmem.c: mark expected switch fall-through
mm/page_alloc.c: broken deferred calculation
mm: don't warn about allocations which stall for too long
fs: fuse: account fuse_inode slab memory as reclaimable
mm, page_alloc: fix potential false positive in __zone_watermark_ok
mm: mlock: remove lru_add_drain_all()
mm, sysctl: make NUMA stats configurable
shmem: convert shmem_init_inodecache() to void
Unify migrate_pages and move_pages access checks
mm, pagevec: rename pagevec drained field
...
As the page free path makes no distinction between cache hot and cold
pages, there is no real useful ordering of pages in the free list that
allocation requests can take advantage of. Juding from the users of
__GFP_COLD, it is likely that a number of them are the result of copying
other sites instead of actually measuring the impact. Remove the
__GFP_COLD parameter which simplifies a number of paths in the page
allocator.
This is potentially controversial but bear in mind that the size of the
per-cpu pagelists versus modern cache sizes means that the whole per-cpu
list can often fit in the L3 cache. Hence, there is only a potential
benefit for microbenchmarks that alloc/free pages in a tight loop. It's
even worse when THP is taken into account which has little or no chance
of getting a cache-hot page as the per-cpu list is bypassed and the
zeroing of multiple pages will thrash the cache anyway.
The truncate microbenchmarks are not shown as this patch affects the
allocation path and not the free path. A page fault microbenchmark was
tested but it showed no sigificant difference which is not surprising
given that the __GFP_COLD branches are a miniscule percentage of the
fault path.
Link: http://lkml.kernel.org/r/20171018075952.10627-9-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
ndo_xdp is a control path callback for setting up XDP in the
driver. We can reuse it for other forms of communication
between the eBPF stack and the drivers. Rename the callback
and associated structures and definitions.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This work enables generic transfer of metadata from XDP into skb. The
basic idea is that we can make use of the fact that the resulting skb
must be linear and already comes with a larger headroom for supporting
bpf_xdp_adjust_head(), which mangles xdp->data. Here, we base our work
on a similar principle and introduce a small helper bpf_xdp_adjust_meta()
for adjusting a new pointer called xdp->data_meta. Thus, the packet has
a flexible and programmable room for meta data, followed by the actual
packet data. struct xdp_buff is therefore laid out that we first point
to data_hard_start, then data_meta directly prepended to data followed
by data_end marking the end of packet. bpf_xdp_adjust_head() takes into
account whether we have meta data already prepended and if so, memmove()s
this along with the given offset provided there's enough room.
xdp->data_meta is optional and programs are not required to use it. The
rationale is that when we process the packet in XDP (e.g. as DoS filter),
we can push further meta data along with it for the XDP_PASS case, and
give the guarantee that a clsact ingress BPF program on the same device
can pick this up for further post-processing. Since we work with skb
there, we can also set skb->mark, skb->priority or other skb meta data
out of BPF, thus having this scratch space generic and programmable
allows for more flexibility than defining a direct 1:1 transfer of
potentially new XDP members into skb (it's also more efficient as we
don't need to initialize/handle each of such new members). The facility
also works together with GRO aggregation. The scratch space at the head
of the packet can be multiple of 4 byte up to 32 byte large. Drivers not
yet supporting xdp->data_meta can simply be set up with xdp->data_meta
as xdp->data + 1 as bpf_xdp_adjust_meta() will detect this and bail out,
such that the subsequent match against xdp->data for later access is
guaranteed to fail.
The verifier treats xdp->data_meta/xdp->data the same way as we treat
xdp->data/xdp->data_end pointer comparisons. The requirement for doing
the compare against xdp->data is that it hasn't been modified from it's
original address we got from ctx access. It may have a range marking
already from prior successful xdp->data/xdp->data_end pointer comparisons
though.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
We should set xdp_xmit only when xdp_do_redirect() succeed.
Cc: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This patch tries to add XDP_REDIRECT for virtio-net. The changes are
not complex as we could use exist XDP_TX helpers for most of the
work. The rest is passing the XDP_TX to NAPI handler for implementing
batching.
Cc: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
There's no need to add packet len average in the case of XDP_PASS
since it will be done soon after skb is created.
Cc: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This change is needed to not fool drop monitor.
(perf record ... -e skb:kfree_skb )
Packets were properly sent and are consumed after TX completion.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The show and store functions don't need/use the attribute.
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Kernel coding style is to put paren around operand of sizeof.
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
The array guest_offloads is local to the source and does not need to
be in global scope, so make it static. Also tweak formatting.
Cleans up sparse warnings:
symbol 'guest_offloads' was not declared. Should it be static?
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Two minor conflicts in virtio_net driver (bug fix overlapping addition
of a helper) and MAINTAINERS (new driver edit overlapping revamp of
PHY entry).
Signed-off-by: David S. Miller <davem@davemloft.net>
Pull networking fixes from David Miller:
1) Handle notifier registry failures properly in tun/tap driver, from
Tonghao Zhang.
2) Fix bpf verifier handling of subtraction bounds and add a testcase
for this, from Edward Cree.
3) Increase reset timeout in ftgmac100 driver, from Ben Herrenschmidt.
4) Fix use after free in prd_retire_rx_blk_timer_exired() in AF_PACKET,
from Cong Wang.
5) Fix SElinux regression due to recent UDP optimizations, from Paolo
Abeni.
6) We accidently increment IPSTATS_MIB_FRAGFAILS in the ipv6 code
paths, fix from Stefano Brivio.
7) Fix some mem leaks in dccp, from Xin Long.
8) Adjust MDIO_BUS kconfig deps to avoid build errors, from Arnd
Bergmann.
9) Mac address length check and buffer size fixes from Cong Wang.
10) Don't leak sockets in ipv6 udp early demux, from Paolo Abeni.
11) Fix return value when copy_from_user() fails in
bpf_prog_get_info_by_fd(), from Daniel Borkmann.
12) Handle PHY_HALTED properly in phy library state machine, from
Florian Fainelli.
13) Fix OOPS in fib_sync_down_dev(), from Ido Schimmel.
14) Fix truesize calculation in virtio_net which led to performance
regressions, from Michael S Tsirkin.
* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net: (76 commits)
samples/bpf: fix bpf tunnel cleanup
udp6: fix jumbogram reception
ppp: Fix a scheduling-while-atomic bug in del_chan
Revert "net: bcmgenet: Remove init parameter from bcmgenet_mii_config"
virtio_net: fix truesize for mergeable buffers
mv643xx_eth: fix of_irq_to_resource() error check
MAINTAINERS: Add more files to the PHY LIBRARY section
ipv4: fib: Fix NULL pointer deref during fib_sync_down_dev()
net: phy: Correctly process PHY_HALTED in phy_stop_machine()
sunhme: fix up GREG_STAT and GREG_IMASK register offsets
bpf: fix bpf_prog_get_info_by_fd to dump correct xlated_prog_len
tcp: avoid bogus gcc-7 array-bounds warning
net: tc35815: fix spelling mistake: "Intterrupt" -> "Interrupt"
bpf: don't indicate success when copy_from_user fails
udp6: fix socket leak on early demux
net: thunderx: Fix BGX transmit stall due to underflow
Revert "vhost: cache used event for better performance"
team: use a larger struct for mac address
net: check dev->addr_len for dev_set_mac_address()
phy: bcm-ns-usb3: fix MDIO_BUS dependency
...
Seth Forshee noticed a performance degradation with some workloads.
This turns out to be due to packet drops. Euan Kemp noticed that this
is because we drop all packets where length exceeds the truesize, but
for some packets we add in extra memory without updating the truesize.
This in turn was kept around unchanged from ab7db91705 ("virtio-net:
auto-tune mergeable rx buffer size for improved performance"). That
commit had an internal reason not to account for the extra space: not
enough bits to do it. No longer true so let's account for the allocated
length exactly.
Many thanks to Seth Forshee for the report and bisecting and Euan Kemp
for debugging the issue.
Fixes: 680557cf79 ("virtio_net: rework mergeable buffer handling")
Reported-by: Euan Kemp <euan.kemp@coreos.com>
Tested-by: Euan Kemp <euan.kemp@coreos.com>
Reported-by: Seth Forshee <seth.forshee@canonical.com>
Tested-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
After removing the reset function, the freeze and restore functions
are now unused when CONFIG_PM_SLEEP is disabled:
drivers/net/virtio_net.c:1881:12: error: 'virtnet_restore_up' defined but not used [-Werror=unused-function]
static int virtnet_restore_up(struct virtio_device *vdev)
drivers/net/virtio_net.c:1859:13: error: 'virtnet_freeze_down' defined but not used [-Werror=unused-function]
static void virtnet_freeze_down(struct virtio_device *vdev)
A more robust way to do this is to remove the #ifdef around the callers
and instead mark them as __maybe_unused. The compiler will now just
silently drop the unused code.
Fixes: 4941d472bf ("virtio-net: do not reset during XDP set")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Unregister the driver before removing multi-instance hotplug
callbacks. This order avoids the warning issued from
__cpuhp_remove_state_cpuslocked when the number of remaining
instances isn't yet zero.
Fixes: 8017c27919 ("net/virtio-net: Convert to hotplug state machine")
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Current XDP implementation wants guest offloads feature to be disabled
on device. This is inconvenient and means guest can't benefit from
offloads if XDP is not used. This patch tries to address this
limitation by disabling the offloads on demand through control guest
offloads. Guest offloads will be disabled and enabled on demand on XDP
set.
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
We currently reset the device during XDP set, the main reason is
that we allocate more headroom with XDP (for header adjustment).
This works but causes network downtime for users.
Previous patches encoded the headroom in the buffer context,
this makes it possible to detect the case where a buffer
with headroom insufficient for XDP is added to the queue and
XDP is enabled afterwards.
Upon detection, we handle this case by copying the packet
(slow, but it's a temporary condition).
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Use ctx API to store headroom for small buffers.
Following patches will retrieve this info and use it for XDP.
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Pack headroom into ctx - this way when we get a buffer we can figure out
the actual headroom that was allocated for the buffer. Will be helpful
to optimize switching between XDP and non-XDP modes which have different
headroom requirements.
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Fixes: commit d45b897b11 ("virtio_net: allow specifying context for rx")
Signed-off-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
We don't hold any tx lock when trying to disable TX during reset, this
would lead a use after free since ndo_start_xmit() tries to access
the virtqueue which has already been freed. Fix this by using
netif_tx_disable() before freeing the vqs, this could make sure no tx
after vq freeing.
Reported-by: Jean-Philippe Menil <jpmenil@gmail.com>
Tested-by: Jean-Philippe Menil <jpmenil@gmail.com>
Fixes commit f600b69050 ("virtio_net: Add XDP support")
Cc: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Robert McCabe <robert.mccabe@rockwellcollins.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Add support to virtio_net to report bpf_prog ID during XDP_QUERY_PROG.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: Jason Wang <jasowang@redhat.com>
Acked-by: Alexei Starovoitov <ast@fb.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
A common pattern with skb_put() is to just want to memcpy()
some data into the new space, introduce skb_put_data() for
this.
An spatch similar to the one for skb_put_zero() converts many
of the places using it:
@@
identifier p, p2;
expression len, skb, data;
type t, t2;
@@
(
-p = skb_put(skb, len);
+p = skb_put_data(skb, data, len);
|
-p = (t)skb_put(skb, len);
+p = skb_put_data(skb, data, len);
)
(
p2 = (t2)p;
-memcpy(p2, data, len);
|
-memcpy(p, data, len);
)
@@
type t, t2;
identifier p, p2;
expression skb, data;
@@
t *p;
...
(
-p = skb_put(skb, sizeof(t));
+p = skb_put_data(skb, data, sizeof(t));
|
-p = (t *)skb_put(skb, sizeof(t));
+p = skb_put_data(skb, data, sizeof(t));
)
(
p2 = (t2)p;
-memcpy(p2, data, sizeof(*p));
|
-memcpy(p, data, sizeof(*p));
)
@@
expression skb, len, data;
@@
-memcpy(skb_put(skb, len), data, len);
+skb_put_data(skb, data, len);
(again, manually post-processed to retain some comments)
Reviewed-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
commit d85b758f72 ("virtio_net: fix support for small rings")
was supposed to increase the buffer size for small rings but had an
unintentional side effect of decreasing it for large rings. This seems
to break some setups - it's not yet clear why, but increasing buffer
size back to what it was before helps.
Fixes: d85b758f72 ("virtio_net: fix support for small rings")
Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Reported-by: "J. Bruce Fields" <bfields@fieldses.org>
Tested-by: Mikulas Patocka <mpatocka@redhat.com>
Tested-by: "J. Bruce Fields" <bfields@fieldses.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Since virtio does not provide it's own ndo_features_check handler,
TSO, and now checksum offload, are disabled for stacked vlans.
Re-enable the support and let the host take care of it. This
restores/improves Guest-to-Guest performance over Q-in-Q vlans.
Acked-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Vladislav Yasevich <vyasevic@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
A bunch of changes to virtio, most affecting virtio net.
ptr_ring batched zeroing - first of batching enhancements
that seems ready.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost
Pull virtio updates from Michael Tsirkin:
"Fixes, cleanups, performance
A bunch of changes to virtio, most affecting virtio net. Also ptr_ring
batched zeroing - first of batching enhancements that seems ready."
* tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost:
s390/virtio: change maintainership
tools/virtio: fix spelling mistake: "wakeus" -> "wakeups"
virtio_net: tidy a couple debug statements
ptr_ring: support testing different batching sizes
ringtest: support test specific parameters
ptr_ring: batch ring zeroing
virtio: virtio_driver doc
virtio_net: don't reset twice on XDP on/off
virtio_net: fix support for small rings
virtio_net: reduce alignment for buffers
virtio_net: rework mergeable buffer handling
virtio_net: allow specifying context for rx
virtio: allow extra context per descriptor
tools/virtio: fix build breakage
virtio: add context flag to find vqs
virtio: wrap find_vqs
ringtest: fix an assert statement
We are printing a decimal value for truesize so we shouldn't use an "0x"
prefix.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
We already do a reset once in remove_vq_common -
there appears to be no point in doing another one
when we add/remove XDP.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
When ring size is small (<32 entries) making buffers smaller means a
full ring might not be able to hold enough buffers to fit a single large
packet.
Make sure a ring full of buffers is large enough to allow at least one
packet of max size.
Fixes: 2613af0ed1 ("virtio_net: migrate mergeable rx buffers to page frag allocators")
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
We don't need to align length to any particular
value anymore. Aligning to L1 cache size probably
sill makes sense to reduce false sharing.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Small follow-up to d74a32acd5 ("xdp: use netlink extended ACK reporting")
in order to let drivers all use the same NL_SET_ERR_MSG_MOD() helper macro
for reporting. This also ensures that we consistently add the driver's
prefix for dumping the report in user space to indicate that the error
message is driver specific and not coming from core code. Furthermore,
NL_SET_ERR_MSG_MOD() now reuses NL_SET_ERR_MSG() and thus makes all macros
check the pointer as suggested.
References: https://www.spinics.net/lists/netdev/msg433267.html
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
We are going to add more parameters to find_vqs, let's wrap the call so
we don't need to tweak all drivers every time.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Try to carry error messages to the user via the netlink extended
ack message attribute.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Avoid hashing the tx napi struct into napi_hash[], which is used for
busy polling receive queues.
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
As of tx napi, device down (`ip link set dev $dev down`) hangs unless
tx napi is enabled. Else napi_enable is not called, so napi_disable
will spin on test_and_set_bit NAPI_STATE_SCHED.
Only call napi_disable if tx napi is enabled.
Fixes: 5a719c2552ca ("virtio-net: transmit napi")
Reported-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Tx napi mode increases the rate of transmit interrupts. Suppress some
by masking interrupts while more packets are expected. The interrupts
will be reenabled before the last packet is sent.
This optimization reduces the througput drop with tx napi for
unidirectional flows such as UDP_STREAM that do not benefit from
cleaning tx completions in the the receive napi handler.
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Amortize the cost of virtual interrupts by doing both rx and tx work
on reception of a receive interrupt if tx napi is enabled. With
VIRTIO_F_EVENT_IDX, this suppresses most explicit tx completion
interrupts for bidirectional workloads.
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
An upcoming patch will call free_old_xmit_skbs indirectly from
virtnet_poll. Move the function above this to avoid having to
introduce a forward declaration.
This is a pure move: no code changes.
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Convert virtio-net to a standard napi tx completion path. This enables
better TCP pacing using TCP small queues and increases single stream
throughput.
The virtio-net driver currently cleans tx descriptors on transmission
of new packets in ndo_start_xmit. Latency depends on new traffic, so
is unbounded. To avoid deadlock when a socket reaches its snd limit,
packets are orphaned on tranmission. This breaks socket backpressure,
including TSQ.
Napi increases the number of interrupts generated compared to the
current model, which keeps interrupts disabled as long as the ring
has enough free descriptors. Keep tx napi optional and disabled for
now. Follow-on patches will reduce the interrupt cost.
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
