taskqueued interrupt mode is going to be quite complex. Since
the polling mode is considered legacy feature for em(4) driver,
the decision is made to make polling and new interrupt handler
mutually exclusive, selected at compile time.
If kernel is compiled with DEVICE_POLLING, the fast taskqueued
interrupt handler code is disabled and the em_poll() and legacy
em_intr() functions are enabled. Otherwise, legacy functions
are disabled and only em_intr_fast() code is compiled.
Discussed with: scottl
new chips and improves support for already supported ones.
Some details, important for future merges:
- if_em.c merged manually, viewing diff between new vendor
driver and previous one.
- if_em_hw.h dropped in from vendor, and then restored revisions
1.16, 1.17, 1.18.
- if_em_hw.c dropped in from vendor, and then two liner change made,
that restores support for two rare chips.
- In em_attach() remove em_check_for_link(). Not needed here, since
already done in em_hardware_init().
- In em_attach() replace the printing block with call to
em_update_link_status().
- Remove modification of sc->link_state from em_hardware_init() and
from em_media_status(). This makes em_update_link_status() a
single point of change. Call em_update_link_status() where needed.
- Restart watchdog if we *did* processed any descriptors. [1]
- Log the watchdog event if the link is *up*. [2]
PR: kern/92948 [1]
Submitted by: Mihail Balikov <mihail.balikov interbgc.com> [1]
PR: kern/92895 [2]
Submitted by: Vladimir Ivanov <wawa yandex-team.ru> [2]
hacking:
- Remove all spaces at eol.
- Improve style(9) in most frequently edited functions.
- In em_encap() push variables for 82544 workaround in the block
where they are only used.
- In em_get_buf() remove unused variable.
taskqueue_start_threads(struct taskqueue **, int count, int pri,
const char *name, ...);
This allows the creation of 1 or more threads that will service a single
taskqueue. Also rework the taskqueue_create() API to remove the API change
that was introduced a while back. Creating a taskqueue doesn't rely on
the presence of a process structure, and the proc mechanics are much better
encapsulated in taskqueue_start_threads(). Also clean up the
taskqueue_terminate() and taskqueue_free() functions to safely drain
pending tasks and remove all associated threads.
The TASKQUEUE_DEFINE and TASKQUEUE_DEFINE_THREAD macros have been changed
to use the new API, but drivers compiled against the old definitions will
still work. Thus, recompiling drivers is not a strict requirement.
the the interface has been configured. I'm not sure how this could ever
have worked before, but it should be fixed now. Also break out the interrupt
degresitration function into it's own step.
- Only update the rx ring consumer pointer after running through the rx loop,
not with each iteration through the loop.
- If possible, use a fast interupt handler instead of an ithread handler. Use
the interrupt handler to check and squelch the interrupt, then schedule a
taskqueue to do the actual work. This has three benefits:
- Eliminates the 'interrupt aliasing' problem found in many chipsets by
allowing the driver to mask the interrupt in the NIC instead of the
OS masking the interrupt in the APIC.
- Allows the driver to control the amount of work done in the interrupt
handler. This results in what I call 'adaptive polling', where you get
the latency benefits of a quick response to interrupts with the
interrupt mitigation and work partitioning of polling. Polling is still
an option in the driver, but I consider it orthogonal to this work.
- Don't hold the driver lock in the RX handler. The handler and all data
associated is effectively serialized already. This eliminates the cost of
dropping and reaquiring the lock for every receieved packet. The result
is much lower contention for the driver lock, resulting in lower CPU usage
and lower latency for interactive workloads.
The amount of work done in the taskqueue is controlled by the sysctl
dev.em.N.rx_processing_limit
and tunable
hw.em.rx_process_limit
Setting these to -1 effectively removes the limit.
The fast interrupt and taskqueue can be disabled by defining NO_EM_FASTINTR.
This work has been shown to increase fast-forwarding from ~570 kpps to
~750 kpps (note that the same NIC hardware seems unable to transmit more than
800 kpps, so this increase appears to be limited almost solely by the
hardware). Gains have been shown in other workloads, ranging from better
performance to elimination of over-saturation livelocks.
Thanks to Andre Opperman for his time and resources from his network
performance project in performing much of the testing. Thanks to Gleb
Smirnoff and Danny Braniss for their help in testing also.
case if memory allocation failed.
- Remove fourth argument from VLAN_INPUT_TAG(), that was used
incorrectly in almost all drivers. Indicate failure with
mbuf value of NULL.
In collaboration with: yongari, ru, sam
- don't force busdma to pre-allocate bounce pages for parent tag.
- use system supplied roundup2 macro instead of rolling its own version.
- TX/RX decriptor length should be multiple of 128. There is no
no need to expand the size with the multiple of 4096.
- don't create/destroy DMA maps in TX/RX handlers. Use pre-allocated
DMA maps. Since creating DMA maps on sparc64 is time consuming
operations(resource mananger overhead), this change should boost
performance on sparc64. I could get > 2x speedup on Ultra60.
- TX/RX descriptors could be aligned on 128 boundary. Aligning them
on PAGE_SIZE is waste of resource.
- don't blindly create TX DMA tag with size of MCLBYTES * 8. The size
is only valid under jumbo frame environments. Instead of using the
hardcoded value, re-compute necessary size on the fly.
- RX side bus_dmamap_load_mbuf_sg(9) support.
- remove unused macro EM_ROUNDUP and constant EM_MMBA.
Reviewed by: scottl
Tested by: glebius
for a notebook with em(4) adapter.
- Introduce tunables em.hw.txd and em.hw.rxd, which allow administrator
to configure number of transmit and receive descriptors.
- Check em.hw.txd and em.hw.rxd against hardware limits [*] and require
them to be multiple of 128.
[*] According to comments in if_em.h the 82540EM/82541ER chips can handle
more than 256 descriptors. Since we don't have this hardware to test,
we decided to mimic NetBSD wm(4) driver, that limits these chips to
256 descriptors.
In collaboration with: yongari
rather than in ifindex_table[]; all (except one) accesses are
through ifp anyway. IF_LLADDR() works faster, and all (except
one) ifaddr_byindex() users were converted to use ifp->if_addr.
- Stop storing a (pointer to) Ethernet address in "struct arpcom",
and drop the IFP2ENADDR() macro; all users have been converted
to use IF_LLADDR() instead.
overruns and number of watchdog timeouts.
- Do not log(9) RX overrun events, since this pessimizes
things under load [1].
- Do not increase if->if_oerrors in em_watchdog(), since
this leads to counter slipping back, when if->if_oerrors
is recalculated in em_update_stats_counters(). Instead
increase watchdog counter in em_watchdog() and take it
into account in em_update_stats_counters().
Submitted by: ade [1]
- disable jumbo frame support on strict alignment architectures due
to the limitation of hardware. The driver needs a fix-up code for
RX side. The fix will show up in near future.
- fix endian issue for 82544 on PCI-X bus. I couldn't test this as
I don't have the NIC/hardware.
- prefer PCIR_BAR to hardcoded EM_MMBA.
- Properly checks for for 64bit BAR [1]
- replace inl/outl with bus_space(9) [1]
- fix endian issue on VLAN handling.
- reorder header files and remove unnecessary one.
Reviewed by: cognet
No response from: pdeuskar, tackerman
Obtained from: OpenBSD [1]
since the link takes a bit to negotiate, the information is pretty
much never available during the probe. As such, the boot output
pretty much always prints N/A for speed and duplex. Since we print
out the output of ifconfig during the user space boot, this early
boot information is also generally redundant, and added to the noise.
MFC after: 2 weeks
- Destroy mutex in case of attach failure. [1]
- Lock properly em_watchdog(). [1]
- Lock properly em_sysctl_int_delay(). [1]
- Remove unused global adapter linked list.
- Remove unused dma_size field from struct em_dma_alloc.
- Do not touch interface statistics, that must be edited
only by upper layers. [1]
Submitted by: yongari [1]
o Do not mask the RX overrun interrupt.
o Rewrite em_intr():
- Axe EM_MAX_INTR.
- Cycle acknowledging interrupts and processing
packets until zero interrupt cause register is
read.
- If RX overrun comes in log this fact. [ NetBSD also
resets adapter in this case, but my tests showed that
this is not needed and only pessimizes behavior under
heavy load. ]
- Since almost all functions is rewritten, style the
remaining lines.
This fixes em(4) interfaces wedging under high load.
In collaboration with: wpaul, cognet
Obtained from: NetBSD
flag. This fixes panic, when 'ifconfig em0 down' was called and it calls
em_stop() while the em_process_receive_interrupts() has temporarily
dropped the lock.
the descriptors set.
- In em_process_receive_interrupts(), call bus_dmamap_sync() for the
descriptors set each time we modify one descriptor, instead of doing it only
at the function exit, to make sure the adapters know he can re-use the
descriptor.
This helps on arm with write-back data cache (and possibly on other arches
with bounce pages, I don't know) under heavy network load. Without this,
if we attempt to process more than num_rx_desc descriptors, the adapter
would just stop processing rx interrupts.
The receive function em_process_receive_interrupts() unlocks the
adapter while ether_input() processes the packet, and then locks
it back. In the meantime, em_init() may be called, either from
em_watchdog() from softclock interrupt or from the ifconfig(8)
program. The em_init() resets the card, in particular it sets
adapter->next_rx_desc_to_check to 0 and resets hardware RX Head
and Tail descriptor pointers. The loop in
em_process_receive_interrupts() does not expect these things to
change, and a mess may result.
This fixes long wedges of em(4) interfaces receive part under high
load and IP fastforwarding enabled.
PR: kern/87418
Submitted by: Dmitrij Tejblum <tejblum yandex-team.ru>
opt_device_polling.h
- Include opt_device_polling.h into appropriate files.
- Embrace with HAVE_KERNEL_OPTION_HEADERS the include in the files that
can be compiled as loadable modules.
Reviewed by: bde
o Axe poll in trap.
o Axe IFF_POLLING flag from if_flags.
o Rework revision 1.21 (Giant removal), in such a way that
poll_mtx is not dropped during call to polling handler.
This fixes problem with idle polling.
o Make registration and deregistration from polling in a
functional way, insted of next tick/interrupt.
o Obsolete kern.polling.enable. Polling is turned on/off
with ifconfig.
Detailed kern_poll.c changes:
- Remove polling handler flags, introduced in 1.21. The are not
needed now.
- Forget and do not check if_flags, if_capenable and if_drv_flags.
- Call all registered polling handlers unconditionally.
- Do not drop poll_mtx, when entering polling handlers.
- In ether_poll() NET_LOCK_GIANT prior to locking poll_mtx.
- In netisr_poll() axe the block, where polling code asks drivers
to unregister.
- In netisr_poll() and ether_poll() do polling always, if any
handlers are present.
- In ether_poll_[de]register() remove a lot of error hiding code. Assert
that arguments are correct, instead.
- In ether_poll_[de]register() use standard return values in case of
error or success.
- Introduce poll_switch() that is a sysctl handler for kern.polling.enable.
poll_switch() goes through interface list and enabled/disables polling.
A message that kern.polling.enable is deprecated is printed.
Detailed driver changes:
- On attach driver announces IFCAP_POLLING in if_capabilities, but
not in if_capenable.
- On detach driver calls ether_poll_deregister() if polling is enabled.
- In polling handler driver obtains its lock and checks IFF_DRV_RUNNING
flag. If there is no, then unlocks and returns.
- In ioctl handler driver checks for IFCAP_POLLING flag requested to
be set or cleared. Driver first calls ether_poll_[de]register(), then
obtains driver lock and [dis/en]ables interrupts.
- In interrupt handler driver checks IFCAP_POLLING flag in if_capenable.
If present, then returns.This is important to protect from spurious
interrupts.
Reviewed by: ru, sam, jhb
make function reenterable. In the runtime the race is masked by serializing
of em_process_receive_interrupts() either by interrupt thread, or by
polling. The race can be triggered when polling is switched on or off.
