If we wait for the once-per-second cleanup to free transmit SKBs,
sockets with small transmit buffer sizes might spend most of their
time blocked waiting for the cleanup.
Normally we do a cleanup for each transmitted packet. We add a
watchdog type timer so that we also schedule a timeout for 150uS after
a packet is transmitted. The watchdog is reset for each transmitted
packet, so for high packet rates, it never expires. At these high
rates, the cleanups are done for each packet so the extra watchdog
initiated cleanups are neither needed nor triggered.
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
To: netdev@vger.kernel.org
To: gregkh@suse.de
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Patchwork: http://patchwork.linux-mips.org/patch/968/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This version has spelling and comment changes based on feedback from
Eric Dumazet.
Stop the queue if too many packets are queued. Restart it from a high
resolution timer.
Rearrange and simplify locking and SKB freeing code
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
To: gregkh@suse.de
Patchwork: http://patchwork.linux-mips.org/patch/843/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
The existing code had the following race:
Thread-1 Thread-2
inc/read in_use
inc/read in_use
inc tx_free_list[qos].len
inc tx_free_list[qos].len
The actual in_use value was incremented twice, but thread-1 is going
to free memory based on its stale value, and will free one too many
times. The result is that memory is freed back to the kernel while
its packet is still in the transmit buffer. If the memory is
overwritten before it is transmitted, the hardware will put a valid
checksum on it and send it out (just like it does with good packets).
If by chance the TCP flags are clobbered but not the addresses or
ports, the result can be a broken TCP stream.
The fix is to track the number of freed packets in a single location
(a Fetch-and-Add Unit register). That way it can never get out of sync
with itself.
We try to free up to MAX_SKB_TO_FREE (currently 10) buffers at a time.
If fewer are available we adjust the free count with the difference.
The action of claiming buffers to free is atomic so two threads cannot
claim the same buffers.
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
The octeon-ethernet driver supports the sgmii, rgmii, spi, and xaui
ports present on the Cavium OCTEON family of SOCs. These SOCs are
multi-core mips64 processors with existing support over in arch/mips.
The driver files can be categorized into three basic groups:
1) Register definitions, these are named cvmx-*-defs.h
2) Main driver code, these have names that don't start cvmx-.
3) Interface specific functions and other utility code, names starting
with cvmx-
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
David Daney