Skip to content

L
linux
Switch branch/tag
  1. 16 Oct, 2021 34 commits
  3. 15 Oct, 2021 6 commits
    • Maciej Fijalkowski's avatar
      ice: make use of ice_for_each_* macros · 2faf63b6
      Maciej Fijalkowski authored 
      Go through the code base and use ice_for_each_* macros.  While at it,
introduce ice_for_each_xdp_txq() macro that can be used for looping over
xdp_rings array.

Commit is not introducing any new functionality.
Signed-off-by: default avatarMaciej Fijalkowski <maciej.fijalkowski@intel.com>
Tested-by: default avatarGurucharan G <gurucharanx.g@intel.com>
Signed-off-by: default avatarTony Nguyen <anthony.l.nguyen@intel.com>
      2faf63b6
    • Maciej Fijalkowski's avatar
      ice: introduce XDP_TX fallback path · 22bf877e
      Maciej Fijalkowski authored 
      Under rare circumstances there might be a situation where a requirement
of having XDP Tx queue per CPU could not be fulfilled and some of the Tx
resources have to be shared between CPUs. This yields a need for placing
accesses to xdp_ring inside a critical section protected by spinlock.
These accesses happen to be in the hot path, so let's introduce the
static branch that will be triggered from the control plane when driver
could not provide Tx queue dedicated for XDP on each CPU.

Currently, the design that has been picked is to allow any number of XDP
Tx queues that is at least half of a count of CPUs that platform has.
For lower number driver will bail out with a response to user that there
were not enough Tx resources that would allow configuring XDP. The
sharing of rings is signalled via static branch enablement which in turn
indicates that lock for xdp_ring accesses needs to be taken in hot path.

Approach based on static branch has no impact on performance of a
non-fallback path. One thing that is needed to be mentioned is a fact
that the static branch will act as a global driver switch, meaning that
if one PF got out of Tx resources, then other PFs that ice driver is
servicing will suffer. However, given the fact that HW that ice driver
is handling has 1024 Tx queues per each PF, this is currently an
unlikely scenario.
Signed-off-by: default avatarMaciej Fijalkowski <maciej.fijalkowski@intel.com>
Tested-by: default avatarGeorge Kuruvinakunnel <george.kuruvinakunnel@intel.com>
Signed-off-by: default avatarTony Nguyen <anthony.l.nguyen@intel.com>
      22bf877e
    • Maciej Fijalkowski's avatar
      ice: optimize XDP_TX workloads · 9610bd98
      Maciej Fijalkowski authored 
      Optimize Tx descriptor cleaning for XDP. Current approach doesn't
really scale and chokes when multiple flows are handled.

Introduce two ring fields, @next_dd and @next_rs that will keep track of
descriptor that should be looked at when the need for cleaning arise and
the descriptor that should have the RS bit set, respectively.

Note that at this point the threshold is a constant (32), but it is
something that we could make configurable.

First thing is to get away from setting RS bit on each descriptor. Let's
do this only once NTU is higher than the currently @next_rs value. In
such case, grab the tx_desc[next_rs], set the RS bit in descriptor and
advance the @next_rs by a 32.

Second thing is to clean the Tx ring only when there are less than 32
free entries. For that case, look up the tx_desc[next_dd] for a DD bit.
This bit is written back by HW to let the driver know that xmit was
successful. It will happen only for those descriptors that had RS bit
set. Clean only 32 descriptors and advance the DD bit.

Actual cleaning routine is moved from ice_napi_poll() down to the
ice_xmit_xdp_ring(). It is safe to do so as XDP ring will not get any
SKBs in there that would rely on interrupts for the cleaning. Nice side
effect is that for rare case of Tx fallback path (that next patch is
going to introduce) we don't have to trigger the SW irq to clean the
ring.

With those two concepts, ring is kept at being almost full, but it is
guaranteed that driver will be able to produce Tx descriptors.

This approach seems to work out well even though the Tx descriptors are
produced in one-by-one manner. Test was conducted with the ice HW
bombarded with packets from HW generator, configured to generate 30
flows.

Xdp2 sample yields the following results:
<snip>
proto 17:   79973066 pkt/s
proto 17:   80018911 pkt/s
proto 17:   80004654 pkt/s
proto 17:   79992395 pkt/s
proto 17:   79975162 pkt/s
proto 17:   79955054 pkt/s
proto 17:   79869168 pkt/s
proto 17:   79823947 pkt/s
proto 17:   79636971 pkt/s
</snip>

As that sample reports the Rx'ed frames, let's look at sar output.
It says that what we Rx'ed we do actually Tx, no noticeable drops.
Average:        IFACE   rxpck/s   txpck/s    rxkB/s    txkB/s   rxcmp/s txcmp/s  rxmcst/s   %ifutil
Average:       ens4f1 79842324.00 79842310.40 4678261.17 4678260.38 0.00      0.00      0.00     38.32

with tx_busy staying calm.

When compared to a state before:
Average:        IFACE   rxpck/s   txpck/s    rxkB/s    txkB/s   rxcmp/s txcmp/s  rxmcst/s   %ifutil
Average:       ens4f1 90919711.60 42233822.60 5327326.85 2474638.04 0.00      0.00      0.00     43.64

it can be observed that the amount of txpck/s is almost doubled, meaning
that the performance is improved by around 90%. All of this due to the
drops in the driver, previously the tx_busy stat was bumped at a 7mpps
rate.
Signed-off-by: default avatarMaciej Fijalkowski <maciej.fijalkowski@intel.com>
Tested-by: default avatarGeorge Kuruvinakunnel <george.kuruvinakunnel@intel.com>
Signed-off-by: default avatarTony Nguyen <anthony.l.nguyen@intel.com>
      9610bd98
    • Maciej Fijalkowski's avatar
      ice: propagate xdp_ring onto rx_ring · eb087cd8
      Maciej Fijalkowski authored 
      With rings being split, it is now convenient to introduce a pointer to
XDP ring within the Rx ring. For XDP_TX workloads this means that
xdp_rings array access will be skipped, which was executed per each
processed frame.

Also, read the XDP prog once per NAPI and if prog is present, set up the
local xdp_ring pointer. Reading prog a single time was discussed in [1]
with some concern raised by Toke around dispatcher handling and having
the need for going through the RCU grace period in the ndo_bpf driver
callback, but ice currently is torning down NAPI instances regardless of
the prog presence on VSI.

Although the pointer to XDP ring introduced to Rx ring makes things a
lot slimmer/simpler, I still feel that single prog read per NAPI
lifetime is beneficial.

Further patch that will introduce the fallback path will also get a
profit from that as xdp_ring pointer will be set during the XDP rings
setup.

[1]: https://lore.kernel.org/bpf/87k0oseo6e.fsf@toke.dk/Signed-off-by: default avatarMaciej Fijalkowski <maciej.fijalkowski@intel.com>
Tested-by: default avatarGeorge Kuruvinakunnel <george.kuruvinakunnel@intel.com>
Signed-off-by: default avatarTony Nguyen <anthony.l.nguyen@intel.com>
      eb087cd8
    • Maciej Fijalkowski's avatar
      ice: do not create xdp_frame on XDP_TX · a55e16fa
      Maciej Fijalkowski authored 
      xdp_frame is not needed for XDP_TX data path in ice driver case.
For this data path cleaning of sent descriptor will not happen anywhere
outside of the driver, which means that carrying the information about
the underlying memory model via xdp_frame will not be used. Therefore,
this conversion can be simply dropped, which would relieve CPU a bit.
Signed-off-by: default avatarMaciej Fijalkowski <maciej.fijalkowski@intel.com>
Tested-by: default avatarGeorge Kuruvinakunnel <george.kuruvinakunnel@intel.com>
Signed-off-by: default avatarTony Nguyen <anthony.l.nguyen@intel.com>
      a55e16fa
    • Maciej Fijalkowski's avatar
      ice: unify xdp_rings accesses · 0bb4f9ec
      Maciej Fijalkowski authored 
      There has been a long lasting issue of improper xdp_rings indexing for
XDP_TX and XDP_REDIRECT actions. Given that currently rx_ring->q_index
is mixed with smp_processor_id(), there could be a situation where Tx
descriptors are produced onto XDP Tx ring, but tail is never bumped -
for example pin a particular queue id to non-matching IRQ line.

Address this problem by ignoring the user ring count setting and always
initialize the xdp_rings array to be of num_possible_cpus() size. Then,
always use the smp_processor_id() as an index to xdp_rings array. This
provides serialization as at given time only a single softirq can run on
a particular CPU.
Signed-off-by: default avatarMaciej Fijalkowski <maciej.fijalkowski@intel.com>
Tested-by: default avatarGeorge Kuruvinakunnel <george.kuruvinakunnel@intel.com>
Signed-off-by: default avatarTony Nguyen <anthony.l.nguyen@intel.com>
      0bb4f9ec
GitLab Nexedi Edition | About GitLab | About Nexedi | 沪ICP备2021021310号-2 | 沪ICP备2021021310号-7