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  1. 14 Oct, 2020 18 commits
  3. 13 Oct, 2020 4 commits
    • Jakub Kicinski's avatar
      Merge branch 'macb-support-the-2-deep-Tx-queue-on-at91' · c93c5482
      Jakub Kicinski authored 
      Willy Tarreau says:

====================
macb: support the 2-deep Tx queue on at91

while running some tests on my Breadbee board, I noticed poor network
Tx performance. I had a look at the driver (macb, at91ether variant)
and noticed that at91ether_start_xmit() immediately stops the queue
after sending a frame and waits for the interrupt to restart the queue,
causing a dead time after each packet is sent.

The AT91RM9200 datasheet states that the controller supports two frames,
one being sent and the other one being queued, so I performed minimal
changes to support this. The transmit performance on my board has
increased by 50% on medium-sized packets (HTTP traffic), and with large
packets I can now reach line rate.

Since this driver is shared by various platforms, I tried my best to
isolate and limit the changes as much as possible and I think it's pretty
reasonable as-is. I've run extensive tests and couldn't meet any
unexpected situation (no stall, overflow nor lockup).

There are 3 patches in this series. The first one adds the missing
interrupt flag for RM9200 (TBRE, indicating the tx buffer is willing
to take a new packet). The second one replaces the single skb with a
2-array and uses only index 0. It does no other change, this is just
to prepare the code for the third one. The third one implements the
queue. Packets are added at the tail of the queue, the queue is
stopped at 2 packets and the interrupt releases 0, 1 or 2 depending
on what the transmit status register reports.
====================
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
      c93c5482
    • Willy Tarreau's avatar
      macb: support the two tx descriptors on at91rm9200 · 0a4e9ce1
      Willy Tarreau authored 
      The at91rm9200 variant used by a few chips including the MSC313 supports
two Tx descriptors (one frame being serialized and another one queued).
However the driver only implemented a single one, which adds a dead time
after each transfer to receive and process the interrupt and wake the
queue up, preventing from reaching line rate.

This patch implements a very basic 2-deep queue to address this limitation.
The tests run on a Breadbee board equipped with an MSC313E show that at
1 GHz, HTTP traffic on medium-sized objects (45kB) was limited to exactly
50 Mbps before this patch, and jumped to 76 Mbps with this patch. And tests
on a single TCP stream with an MTU of 576 jump from 10kpps to 15kpps. With
1500 byte packets it's now possible to reach line rate versus 75 Mbps
before.

Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: Claudiu Beznea <claudiu.beznea@microchip.com>
Cc: Daniel Palmer <daniel@0x0f.com>
Signed-off-by: default avatarWilly Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/r/20201011090944.10607-4-w@1wt.euSigned-off-by: default avatarJakub Kicinski <kuba@kernel.org>
      0a4e9ce1
    • Willy Tarreau's avatar
      macb: prepare at91 to use a 2-frame TX queue · 73d74228
      Willy Tarreau authored 
      The RM9200 supports one frame being sent while another one is waiting in
queue. This avoids the dead time that follows the emission of a frame
and which prevents one from reaching line speed.

Right now the driver supports only a single skb, so we'll first replace
the rm9200-specific skb info with an array of two macb_tx_skb (already
used by other drivers). This patch only moves the skb_length to
txq[0].size and skb_physaddr to skb[0].mapping but doesn't perform any
other change. It already uses [desc] in order to minimize future changes.

Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: Claudiu Beznea <claudiu.beznea@microchip.com>
Cc: Daniel Palmer <daniel@0x0f.com>
Signed-off-by: default avatarWilly Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/r/20201011090944.10607-3-w@1wt.euSigned-off-by: default avatarJakub Kicinski <kuba@kernel.org>
      73d74228
    • Willy Tarreau's avatar
      macb: add RM9200's interrupt flag TBRE · fa6031df
      Willy Tarreau authored 
      Transmit Buffer Register Empty replaces TXERR on RM9200 and signals the
sender may try to send again becase the last queued frame is no longer
in queue (being transmitted or already transmitted).

Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: Claudiu Beznea <claudiu.beznea@microchip.com>
Cc: Daniel Palmer <daniel@0x0f.com>
Signed-off-by: default avatarWilly Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/r/20201011090944.10607-2-w@1wt.euSigned-off-by: default avatarJakub Kicinski <kuba@kernel.org>
      fa6031df
  5. 12 Oct, 2020 18 commits
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