I am experiencing network data corruption with a 3Com 3C996B-T NIC
(Broadcom NetXtreme BCM5701; driver tg3.ko). I have identified the
following patch as the trigger:
commit fb93134dfc2a6e6fbedc7c270a31da03fce88db9
Author: Herbert Xu <[email protected]>
Date: Wed Nov 14 15:45:21 2007 -0800
[TCP]: Fix size calculation in sk_stream_alloc_pskb
We round up the header size in sk_stream_alloc_pskb so that
TSO packets get zero tail room. Unfortunately this rounding
up is not coordinated with the select_size() function used by
TCP to calculate the second parameter of sk_stream_alloc_pskb.
As a result, we may allocate more than a page of data in the
non-TSO case when exactly one page is desired.
In fact, rounding up the head room is detrimental in the non-TSO
case because it makes memory that would otherwise be available to
the payload head room. TSO doesn't need this either, all it wants
is the guarantee that there is no tail room.
So this patch fixes this by adjusting the skb_reserve call so that
exactly the requested amount (which all callers have calculated in
a precise way) is made available as tail room.
Signed-off-by: Herbert Xu <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
This patch was included in 2.6.24 and 2.6.23.4 -stable. I am
experiencing data corruption with kernels 2.6.23.4 - 2.6.23.16, 2.6.24 -
2.6.24.2, and 2.6.25-rc2-git1. I have verified that reverting the above
patch (by hand) makes the data corruption go away on all affected
kernels (note that in 2.6.25 the function is sk_stream_alloc_skb() in
net/ipv4/tcp.c rather than sk_stream_alloc_pskb() in include/net/sock.h).
(Also note that when testing 2.6.23 - 2.6.23.4, I had to apply the
individual patch "TG3: Fix performance regression on 5705." from 2.6.23.5.)
I do not get data corruption when substituting a SysKonnect 9D21 NIC
(which also uses the tg3.ko driver) or a Intel PRO/1000 82546GB NIC
(which uses the e1000.ko driver).
In addition to the 3Com NIC, my computer has a SCSI HBA with an attached
tape drive. The network data corruption happens only when reading from
or writing to the tape drive. I have tried both a LSI MPT Fusion
Ultra320 SCSI HBA (mptspi.ko) and a LSI 53c1010 Ultra160 HBA
(sym53c8xx.ko) with the same results. The NIC and SCSI HBA are on
separate PCI-X buses and do not share IRQs. I am using two completely
separate test programs to access the SCSI tape drive and test network
data integrity, so one would expect no interaction between the two tests
other than CPU scheduling and DMA bandwidth. There is no disk I/O
generated by either test program.
The test program that I am using to debug this problem does the following:
Computer A (kernel 2.6.24.2; 3Com 3C996B-T NIC):
malloc a 64 KB buf aligned to a 4 KB boundary
loop {
fill 64 KB buf with count data pattern
send(64 KB, MSG_MORE) <--- eventually sends corrupted data
}
(SCSI tape drive test program runs separately in the background)
Computer B (kernel 2.6.12):
malloc a 64 KB buf aligned to a 4 KB boundary
loop {
recv(64 KB, MSG_WAITALL)
verify count data pattern in 64 KB buf
}
After running for a few seconds, the verify on computer B detects data
corruption in the last 4 bytes of the 64 KB buffer. The last 48 bytes
of the corrupted 64 KB buffer look like this:
D0 D1 D2 D3 | D4 D5 D6 D7 | D8 D9 DA DB | DC DD DE DF
E0 E1 E2 E3 | E4 E5 E6 E7 | E8 E9 EA EB | EC ED EE EF
F0 F1 F2 F3 | F4 F5 F6 F7 | F8 F9 FA FB | F4 F5 F6 F7
The last 4 bytes should be "FC FD FE FF" but instead are corrupted to
"F4 F5 F6 F7", a sequence which came earlier in the data stream. The
data corruption always occurs at this same buffer offset and with the
same 4 earlier bytes duplicated. However, it occurs on a different
iteration of the send()/recv() loop each time the test is run.
When I reverse the test so that Computer A does recv() and Computer B
does send(), the test passes with no data corruption. Therefore, it
appears that the data corruption happens on send() but not recv().
The motherboard that I am using is a Commell LV-672. This motherboard
has a PCI-express x16 slot but no PCI-X slots. To plug in the PCI-X NIC
and SCSI HBA, I am using a SuperMicro CSE-RR2UE-AX riser card which
plugs into the PCI-express slot on the motherboard and provides 3 PCI-X
slots (two slots together on one PCI-X bus and one slot on its own PCI-X
bus). The data corruption happens with every combination of the 2 cards
in the 3 slots.
I assume that the above patch is just exposing some way in which the tg3
driver or the BCM5701 chip are broken. For now, I am just reverting the
above patch for kernels that I use until a better solution is
forthcoming. I expect that this problem will be difficult for other
developers to reproduce, but I can test any patches that anyone wants to
send me. [ In the meantime, should we revert the patch for 2.6.23.x and
2.6.24.x -stable, or wait for a fix to tg3? ]
I am not sure if it is relevant, but I am also getting the following
messages sometimes during testing:
Clocksource tsc unstable (delta = 64002086 ns)
Time: pit clocksource has been installed.
This seems bogus because the CPU is a Intel Pentium 4 with
HyperThreading, so the tsc should be reliable.
---
network MTU = 1500
lspci
00:00.0 Host bridge: Intel Corporation 82915G/P/GV/GL/PL/910GL Memory
Controller Hub (rev 0e)
00:01.0 PCI bridge: Intel Corporation 82915G/P/GV/GL/PL/910GL PCI
Express Root Port (rev 0e)
00:02.0 VGA compatible controller: Intel Corporation 82915G/GV/910GL
Integrated Graphics Controller (rev 0e)
00:1d.0 USB Controller: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6
Family) USB UHCI #1 (rev 04)
00:1d.1 USB Controller: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6
Family) USB UHCI #2 (rev 04)
00:1d.2 USB Controller: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6
Family) USB UHCI #3 (rev 04)
00:1d.3 USB Controller: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6
Family) USB UHCI #4 (rev 04)
00:1d.7 USB Controller: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6
Family) USB2 EHCI Controller (rev 04)
00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev d4)
00:1f.0 ISA bridge: Intel Corporation 82801FB/FR (ICH6/ICH6R) LPC
Interface Bridge (rev 04)
00:1f.1 IDE interface: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6
Family) IDE Controller (rev 04)
00:1f.3 SMBus: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family)
SMBus Controller (rev 04)
01:00.0 PCI bridge: Intel Corporation 6700PXH PCI Express-to-PCI Bridge
A (rev 09)
01:00.2 PCI bridge: Intel Corporation 6700PXH PCI Express-to-PCI Bridge
B (rev 09)
02:02.0 SCSI storage controller: LSI Logic / Symbios Logic 53c1030 PCI-X
Fusion-MPT Dual Ultra320 SCSI (rev 08)
03:01.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5701
Gigabit Ethernet (rev 15)
04:0d.0 FireWire (IEEE 1394): Agere Systems FW323 (rev 61)
cat /proc/interrupts
CPU0 CPU1
0: 89 0 IO-APIC-edge timer
1: 78 0 IO-APIC-edge i8042
3: 17 0 IO-APIC-edge serial
8: 0 0 IO-APIC-edge rtc
9: 0 0 IO-APIC-fasteoi acpi
12: 5 0 IO-APIC-edge i8042
14: 465 0 IO-APIC-edge ide0
16: 0 0 IO-APIC-fasteoi uhci_hcd:usb5
17: 149220 0 IO-APIC-fasteoi eth0
18: 10007 0 IO-APIC-fasteoi uhci_hcd:usb4, ioc0
19: 29 0 IO-APIC-fasteoi uhci_hcd:usb3
23: 2 0 IO-APIC-fasteoi ehci_hcd:usb1, uhci_hcd:usb2
NMI: 0 0 Non-maskable interrupts
LOC: 7457 10023 Local timer interrupts
RES: 1962 14316 Rescheduling interrupts
CAL: 40 49 function call interrupts
TLB: 39 76 TLB shootdowns
TRM: 0 0 Thermal event interrupts
SPU: 0 0 Spurious interrupts
ERR: 0
MIS: 0
(eth0 == tg3; ioc0 == LSI SCSI HBA)
ifconfig
eth0 Link encap:Ethernet HWaddr 00:02:A5:E7:3C:2D
inet addr:192.168.1.1 Bcast:192.168.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:77198 errors:0 dropped:0 overruns:0 frame:0
TX packets:3488350 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:5403873 (5.1 MiB) TX bytes:1000276920 (953.9 MiB)
Interrupt:17
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
information from ethtool
driver: tg3
version: 3.87
firmware-version:
bus-info: 0000:03:01.0
Settings for eth0:
Supported ports: [ TP ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Half 1000baseT/Full
Supports auto-negotiation: Yes
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Half 1000baseT/Full
Advertised auto-negotiation: Yes
Speed: 1000Mb/s
Duplex: Full
Port: Twisted Pair
PHYAD: 1
Transceiver: internal
Auto-negotiation: on
Supports Wake-on: g
Wake-on: g
Current message level: 0x000000ff (255)
Link detected: yes
Offload parameters for eth0:
rx-checksumming: on
tx-checksumming: on
scatter-gather: on
tcp segmentation offload: off
udp fragmentation offload: off
generic segmentation offload: off
NIC statistics:
rx_octets: 5403873
rx_fragments: 0
rx_ucast_packets: 77197
rx_mcast_packets: 0
rx_bcast_packets: 1
rx_fcs_errors: 0
rx_align_errors: 0
rx_xon_pause_rcvd: 0
rx_xoff_pause_rcvd: 0
rx_mac_ctrl_rcvd: 0
rx_xoff_entered: 0
rx_frame_too_long_errors: 0
rx_jabbers: 0
rx_undersize_packets: 0
rx_in_length_errors: 0
rx_out_length_errors: 0
rx_64_or_less_octet_packets: 2
rx_65_to_127_octet_packets: 77196
rx_128_to_255_octet_packets: 0
rx_256_to_511_octet_packets: 0
rx_512_to_1023_octet_packets: 0
rx_1024_to_1522_octet_packets: 0
rx_1523_to_2047_octet_packets: 0
rx_2048_to_4095_octet_packets: 0
rx_4096_to_8191_octet_packets: 0
rx_8192_to_9022_octet_packets: 0
tx_octets: 1000276920
tx_collisions: 0
tx_xon_sent: 0
tx_xoff_sent: 0
tx_flow_control: 0
tx_mac_errors: 0
tx_single_collisions: 0
tx_mult_collisions: 0
tx_deferred: 0
tx_excessive_collisions: 0
tx_late_collisions: 0
tx_collide_2times: 0
tx_collide_3times: 0
tx_collide_4times: 0
tx_collide_5times: 0
tx_collide_6times: 0
tx_collide_7times: 0
tx_collide_8times: 0
tx_collide_9times: 0
tx_collide_10times: 0
tx_collide_11times: 0
tx_collide_12times: 0
tx_collide_13times: 0
tx_collide_14times: 0
tx_collide_15times: 0
tx_ucast_packets: 3488350
tx_mcast_packets: 0
tx_bcast_packets: 0
tx_carrier_sense_errors: 0
tx_discards: 0
tx_errors: 0
dma_writeq_full: 0
dma_write_prioq_full: 0
rxbds_empty: 0
rx_discards: 0
rx_errors: 0
rx_threshold_hit: 11
dma_readq_full: 2188114
dma_read_prioq_full: 162588
tx_comp_queue_full: 0
ring_set_send_prod_index: 2901128
ring_status_update: 218885
nic_irqs: 146494
nic_avoided_irqs: 72391
nic_tx_threshold_hit: 103584
Tony Battersby
Cybernetics
On Mon, 2008-02-18 at 17:41 -0500, Tony Battersby wrote:
> I am experiencing network data corruption with a 3Com 3C996B-T NIC
> (Broadcom NetXtreme BCM5701; driver tg3.ko). I have identified the
> following patch as the trigger:
Assuming this problem is unique to the 5701, I'm not sure how it is
exposed by Herbert's patch. One thing unique on the 5701 is that it
double-copies all RX packets so that the data starts at offset 2, but
that's quite unrelated to the patch below.
>
> commit fb93134dfc2a6e6fbedc7c270a31da03fce88db9
> Author: Herbert Xu <[email protected]>
> Date: Wed Nov 14 15:45:21 2007 -0800
>
> [TCP]: Fix size calculation in sk_stream_alloc_pskb
>
>
> I do not get data corruption when substituting a SysKonnect 9D21 NIC
> (which also uses the tg3.ko driver)
What Broadcom chip is on the Syskonnect card?
From: "Michael Chan" <[email protected]>
Date: Mon, 18 Feb 2008 16:32:00 -0800
> On Mon, 2008-02-18 at 17:41 -0500, Tony Battersby wrote:
> > I am experiencing network data corruption with a 3Com 3C996B-T NIC
> > (Broadcom NetXtreme BCM5701; driver tg3.ko). I have identified the
> > following patch as the trigger:
>
> Assuming this problem is unique to the 5701, I'm not sure how it is
> exposed by Herbert's patch. One thing unique on the 5701 is that it
> double-copies all RX packets so that the data starts at offset 2, but
> that's quite unrelated to the patch below.
One consequence of Herbert's change is that the chip will see a
different datastream. The initial skb->data linear area will be
smaller, and the transition to the fragmented area of pages will be
quicker.
On Mon, 2008-02-18 at 16:35 -0800, David Miller wrote:
> One consequence of Herbert's change is that the chip will see a
> different datastream. The initial skb->data linear area will be
> smaller, and the transition to the fragmented area of pages will be
> quicker.
>
I see. Perhaps when we get to the end of the data-stream, there is a
tiny frag that the chip cannot handle. That's the only thing I can
think of.
Please try this patch to see if the problem goes away. This will
disable SG on 5701 so we always get linear SKBs.
diff --git a/drivers/net/tg3.c b/drivers/net/tg3.c
index db606b6..bb37e76 100644
--- a/drivers/net/tg3.c
+++ b/drivers/net/tg3.c
@@ -12717,6 +12717,9 @@ static int __devinit tg3_init_one(struct pci_dev *pdev,
} else
tp->tg3_flags &= ~TG3_FLAG_RX_CHECKSUMS;
+ if (GET_ASIC_REV(tp->pci_chip_rev_id) == ASIC_REV_5701)
+ dev->features &= ~(NETIF_F_IP_CSUM | NETIF_F_SG);
+
/* flow control autonegotiation is default behavior */
tp->tg3_flags |= TG3_FLAG_PAUSE_AUTONEG;
tp->link_config.flowctrl = TG3_FLOW_CTRL_TX | TG3_FLOW_CTRL_RX;
Michael Chan wrote:
> On Mon, 2008-02-18 at 16:35 -0800, David Miller wrote:
>
>
>> One consequence of Herbert's change is that the chip will see a
>> different datastream. The initial skb->data linear area will be
>> smaller, and the transition to the fragmented area of pages will be
>> quicker.
>>
>>
>
> I see. Perhaps when we get to the end of the data-stream, there is a
> tiny frag that the chip cannot handle. That's the only thing I can
> think of.
>
> Please try this patch to see if the problem goes away. This will
> disable SG on 5701 so we always get linear SKBs.
>
> diff --git a/drivers/net/tg3.c b/drivers/net/tg3.c
> index db606b6..bb37e76 100644
> --- a/drivers/net/tg3.c
> +++ b/drivers/net/tg3.c
> @@ -12717,6 +12717,9 @@ static int __devinit tg3_init_one(struct pci_dev *pdev,
> } else
> tp->tg3_flags &= ~TG3_FLAG_RX_CHECKSUMS;
>
> + if (GET_ASIC_REV(tp->pci_chip_rev_id) == ASIC_REV_5701)
> + dev->features &= ~(NETIF_F_IP_CSUM | NETIF_F_SG);
> +
> /* flow control autonegotiation is default behavior */
> tp->tg3_flags |= TG3_FLAG_PAUSE_AUTONEG;
> tp->link_config.flowctrl = TG3_FLOW_CTRL_TX | TG3_FLOW_CTRL_RX;
>
>
>
>
This patch does appear to fix the data corruption (tested with
2.6.24.2). However, it results in performance problems with the iSCSI
application that I am trying to run on this machine.
The test program that I described in the previous message still gets
good performance in both directions. "iperf -r" gets good performance
in both directions (940 Mbits/s or 117 MB/s). However, my target-mode
iSCSI application (which obviously generates rx/tx traffic patterns more
complicated than the synthetic tests) gets very poor performance in one
direction but good performance in the other direction. iSCSI
performance drops to 6 - 15 MB/s when the 3Com NIC is doing heavy rx
with light tx, but remains at a decent 115 MB/s when the 3Com NIC is
doing heavy tx with light rx. When I revert Herbert's patch instead of
applying the patch above, I get 115 MB/s in both cases. (With a stock
unpatched kernel, the test fails almost immediately because the iSCSI
control PDUs are corrupted, causing the TCP connection to be dropped.)
The SysKonnect NIC that does not exhibit this problem has a chip that
says "BCM5411KQM" "TT0128 P2Q" and "56975E".
Tony
On Tue, 2008-02-19 at 11:16 -0500, Tony Battersby wrote:
> iSCSI
> performance drops to 6 - 15 MB/s when the 3Com NIC is doing heavy rx
> with light tx,
That's strange. The patch should only affect TX performance slightly
since we are just turning off SG for TX. Please take an ethereal trace
to see what's happening and compare with a good trace.
> but remains at a decent 115 MB/s when the 3Com NIC is
> doing heavy tx with light rx. When I revert Herbert's patch instead
> of
> applying the patch above, I get 115 MB/s in both cases. (With a stock
> unpatched kernel, the test fails almost immediately because the iSCSI
> control PDUs are corrupted, causing the TCP connection to be dropped.)
>
> The SysKonnect NIC that does not exhibit this problem has a chip that
> says "BCM5411KQM" "TT0128 P2Q" and "56975E".
>
I think this is the 5700, but please send me the tg3 output that
identifies the chip and the revision. Something like this:
eth2: Tigon3 [partno(BCM95705) rev 3003 PHY(5705)] (PCI:66MHz:32-bit) 10/100/1000Base-T Ethernet 00:10:18:04:57:0d
eth2: RXcsums[1] LinkChgREG[0] MIirq[0] ASF[0] WireSpeed[0] TSOcap[1]
Michael Chan wrote:
>> The SysKonnect NIC that does not exhibit this problem has a chip that
>> says "BCM5411KQM" "TT0128 P2Q" and "56975E".
> I think this is the 5700, but please send me the tg3 output that
> identifies the chip and the revision. Something like this:
>
> eth2: Tigon3 [partno(BCM95705) rev 3003 PHY(5705)] (PCI:66MHz:32-bit) 10/100/1000Base-T Ethernet 00:10:18:04:57:0d
> eth2: RXcsums[1] LinkChgREG[0] MIirq[0] ASF[0] WireSpeed[0] TSOcap[1]
>
Here is the dmesg output for the SysKonnect NIC:
eth0: Tigon3 [partno(SK-9D21) rev 7104 PHY(5411)] (PCI:66MHz:64-bit)
10/100/1000Base-T Ethernet 00:00:5a:9d:0c:4a
eth0: RXcsums[1] LinkChgREG[1] MIirq[1] ASF[0] WireSpeed[0] TSOcap[0]
eth0: dma_rwctrl[76ff000f] dma_mask[64-bit]
Tony
Michael Chan wrote:
> On Tue, 2008-02-19 at 11:16 -0500, Tony Battersby wrote:
>
>> iSCSI
>> performance drops to 6 - 15 MB/s when the 3Com NIC is doing heavy rx
>> with light tx,
>>
>
> That's strange. The patch should only affect TX performance slightly
> since we are just turning off SG for TX. Please take an ethereal trace
> to see what's happening and compare with a good trace.
>
>
Update: when I revert Herbert's patch in addition to applying your
patch, the iSCSI performance goes back up to 115 MB/s again in both
directions. So it looks like turning off SG for TX didn't itself cause
the performance drop, but rather that the performance drop is just
another manifestation of whatever bug is causing the data corruption.
I do not regularly use wireshark or look at network packet dumps, so I
am not really sure what to look for. Given the above information, do
you still believe that there is value in examining the packet dump?
Tony
On Tue, 2008-02-19 at 17:14 -0500, Tony Battersby wrote:
>
> Update: when I revert Herbert's patch in addition to applying your
> patch, the iSCSI performance goes back up to 115 MB/s again in both
> directions. So it looks like turning off SG for TX didn't itself cause
> the performance drop, but rather that the performance drop is just
> another manifestation of whatever bug is causing the data corruption.
>
> I do not regularly use wireshark or look at network packet dumps, so I
> am not really sure what to look for. Given the above information, do
> you still believe that there is value in examining the packet dump?
>
Can you confirm whether you're getting TCP checksum errors on the other
side that is receiving packets from the 5701? You can just check
statistics using netstat -s. I suspect that after we turn off SG,
checksum is no longer offloaded and we are getting lots of TCP checksum
errors instead that are slowing the performance.
On Tue, Feb 19, 2008 at 05:14:26PM -0500, Tony Battersby wrote:
> Michael Chan wrote:
> > On Tue, 2008-02-19 at 11:16 -0500, Tony Battersby wrote:
> >
> >> iSCSI
> >> performance drops to 6 - 15 MB/s when the 3Com NIC is doing heavy rx
> >> with light tx,
> >>
> >
> > That's strange. The patch should only affect TX performance slightly
> > since we are just turning off SG for TX. Please take an ethereal trace
> > to see what's happening and compare with a good trace.
> >
> >
>
> Update: when I revert Herbert's patch in addition to applying your
> patch, the iSCSI performance goes back up to 115 MB/s again in both
> directions. So it looks like turning off SG for TX didn't itself cause
> the performance drop, but rather that the performance drop is just
> another manifestation of whatever bug is causing the data corruption.
>
> I do not regularly use wireshark or look at network packet dumps, so I
> am not really sure what to look for. Given the above information, do
> you still believe that there is value in examining the packet dump?
>
> Tony
Hi Tony. Can you give us the output of :
sudo lspci -vvv -xxxx -s 03:01.0'
(assuming that is still the correct address of the 3Com NIC.)
Also, after some digging, I found that the 5701 can run into trouble if
a 64-bit DMA read terminates early and then completes as a 32-bit transfer.
The problem is reportedly very rare, but the failure mode looks like a
match. Can you apply the following patch and see if it helps your
performance / corruption problems?
diff --git a/drivers/net/tg3.c b/drivers/net/tg3.c
index db606b6..7ad08ce 100644
--- a/drivers/net/tg3.c
+++ b/drivers/net/tg3.c
@@ -11409,6 +11409,8 @@ static int __devinit tg3_get_invariants(struct tg3 *tp)
tp->tg3_flags |= TG3_FLAG_PCI_HIGH_SPEED;
if ((pci_state_reg & PCISTATE_BUS_32BIT) != 0)
tp->tg3_flags |= TG3_FLAG_PCI_32BIT;
+ else if (GET_ASIC_REV(tp->pci_chip_rev_id) == ASIC_REV_5701)
+ tp->grc_mode |= GRC_MODE_FORCE_PCI32BIT;
/* Chip-specific fixup from Broadcom driver */
if ((tp->pci_chip_rev_id == CHIPREV_ID_5704_A0) &&
On Tue, Feb 19, 2008 at 05:14:26PM -0500, Tony Battersby wrote:
>
> Update: when I revert Herbert's patch in addition to applying your
> patch, the iSCSI performance goes back up to 115 MB/s again in both
> directions. So it looks like turning off SG for TX didn't itself cause
> the performance drop, but rather that the performance drop is just
> another manifestation of whatever bug is causing the data corruption.
Interesting. So the workload that regressed is mostly RX with a
little TX traffic? Can you try to reproduce this with something
like netperf to eliminate other variables?
This is all very puzzling since the patch in question shouldn't
change an RX load at all.
Thanks,
--
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
Michael Chan wrote:
> On Tue, 2008-02-19 at 17:14 -0500, Tony Battersby wrote:
>
>
>> Update: when I revert Herbert's patch in addition to applying your
>> patch, the iSCSI performance goes back up to 115 MB/s again in both
>> directions. So it looks like turning off SG for TX didn't itself cause
>> the performance drop, but rather that the performance drop is just
>> another manifestation of whatever bug is causing the data corruption.
>>
>> I do not regularly use wireshark or look at network packet dumps, so I
>> am not really sure what to look for. Given the above information, do
>> you still believe that there is value in examining the packet dump?
>>
>>
>
> Can you confirm whether you're getting TCP checksum errors on the other
> side that is receiving packets from the 5701? You can just check
> statistics using netstat -s. I suspect that after we turn off SG,
> checksum is no longer offloaded and we are getting lots of TCP checksum
> errors instead that are slowing the performance.
>
>
>
Confirmed. With a 100 MB read/write test, netstat -s shows 75 bad
segments received, and performance in the one direction is about 5
MB/s. When I switch to the SysKonnect NIC, netstat -s shows 0 bad
segments received, and performance is 115 MB/s. So that solves that
mystery - there is still data corruption, but the software-computed TCP
checksum causes the bad packets to be retransmitted rather than being
passed on to the application.
Tony
Herbert Xu wrote:
> On Tue, Feb 19, 2008 at 05:14:26PM -0500, Tony Battersby wrote:
>
>> Update: when I revert Herbert's patch in addition to applying your
>> patch, the iSCSI performance goes back up to 115 MB/s again in both
>> directions. So it looks like turning off SG for TX didn't itself cause
>> the performance drop, but rather that the performance drop is just
>> another manifestation of whatever bug is causing the data corruption.
>>
>
> Interesting. So the workload that regressed is mostly RX with a
> little TX traffic? Can you try to reproduce this with something
> like netperf to eliminate other variables?
>
> This is all very puzzling since the patch in question shouldn't
> change an RX load at all.
>
> Thanks,
>
We have established that the slowdown was caused by TCP checksum errors
and retransmits. I assume that the slowdown in my test was due to the
light TX rather than the heavy RX. I am no TCP protocol expert, but
perhaps heavy TX (such as iperf) might not be affected as much because
the wire stays busy while waiting for the retransmit, whereas with my
light TX iSCSI load, the wire goes idle while waiting for the retransmit
because the iSCSI state machine is stalled.
Tony
Matt Carlson wrote:
> Hi Tony. Can you give us the output of :
>
> sudo lspci -vvv -xxxx -s 03:01.0'
>
03:01.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5701 Gigabit Ethernet (rev 15)
Subsystem: Compaq Computer Corporation NC7770 Gigabit Server Adapter (PCI-X, 10/100/1000-T)
Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
Status: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
Latency: 64 (16000ns min), Cache Line Size: 64 bytes
Interrupt: pin A routed to IRQ 17
Region 0: Memory at df7f0000 (64-bit, non-prefetchable) [size=64K]
[virtual] Expansion ROM at dfc00000 [disabled] [size=64K]
Capabilities: [40] PCI-X non-bridge device
Command: DPERE- ERO- RBC=512 OST=1
Status: Dev=03:01.1 64bit+ 133MHz+ SCD- USC- DC=simple DMMRBC=512 DMOST=1 DMCRS=8 RSCEM- 266MHz- 533MHz-
Capabilities: [48] Power Management version 2
Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot+,D3cold+)
Status: D0 PME-Enable- DSel=0 DScale=1 PME-
Capabilities: [50] Vital Product Data <?>
Capabilities: [58] Message Signalled Interrupts: Mask- 64bit+ Queue=0/3 Enable-
Address: 063000119b608000 Data: 0423
00: e4 14 45 16 06 00 b0 02 15 00 00 02 10 40 00 00
10: 04 00 7f df 00 00 00 00 00 00 00 00 00 00 00 00
20: 00 00 00 00 00 00 00 00 00 00 00 00 11 0e 7c 00
30: 00 00 00 00 40 00 00 00 00 00 00 00 0b 01 40 00
40: 07 48 00 00 09 03 03 00 01 50 02 c0 00 20 00 64
50: 03 58 00 00 08 10 21 08 05 00 86 00 00 80 60 9b
60: 11 00 30 06 23 04 00 00 98 02 05 01 0f 00 db 76
70: 8a 10 00 00 c7 00 00 80 50 00 00 00 00 00 00 00
80: 03 58 00 00 00 00 00 00 34 80 13 04 82 10 00 00
90: 09 06 00 01 00 00 00 00 00 00 00 00 c6 01 00 00
a0: 00 00 00 00 fe 02 00 00 00 00 00 00 af 01 00 00
b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> Also, after some digging, I found that the 5701 can run into trouble if
> a 64-bit DMA read terminates early and then completes as a 32-bit transfer.
> The problem is reportedly very rare, but the failure mode looks like a
> match. Can you apply the following patch and see if it helps your
> performance / corruption problems?
>
>
> diff --git a/drivers/net/tg3.c b/drivers/net/tg3.c
> index db606b6..7ad08ce 100644
> --- a/drivers/net/tg3.c
> +++ b/drivers/net/tg3.c
> @@ -11409,6 +11409,8 @@ static int __devinit tg3_get_invariants(struct tg3 *tp)
> tp->tg3_flags |= TG3_FLAG_PCI_HIGH_SPEED;
> if ((pci_state_reg & PCISTATE_BUS_32BIT) != 0)
> tp->tg3_flags |= TG3_FLAG_PCI_32BIT;
> + else if (GET_ASIC_REV(tp->pci_chip_rev_id) == ASIC_REV_5701)
> + tp->grc_mode |= GRC_MODE_FORCE_PCI32BIT;
>
> /* Chip-specific fixup from Broadcom driver */
> if ((tp->pci_chip_rev_id == CHIPREV_ID_5704_A0) &&
>
>
Sorry, this didn't help. I still get data corruption with hardware
checksumming or poor performance with software checksumming.
Tony
Update:
Herbert's patch alters the arguments to alloc_skb_fclone() and
skb_reserve() from within sk_stream_alloc_pskb(). This changes the
skb_headroom() and skb_tailroom() of the returned skb. I decided to see
if I could detect the precise point at which data corruption started to
happen. The result is this table:
(sk_stream_alloc_pskb() called with size == 1448;
sk->sk_prot->max_header == 160)
skb_headroom skb_tailroom test result note
216 1448 fail [1]
344 1448 fail
340 1452 pass
336 1456 pass
332 1460 pass
328 1464 fail
324 1468 pass
320 1472 pass
316 1476 pass
312 1480 fail
308 1484 pass
304 1488 pass
300 1492 pass
296 1496 fail
292 1500 pass
288 1504 pass
284 1508 pass
280 1512 fail
276 1516 pass
272 1520 pass
268 1524 pass
264 1528 fail
260 1532 pass
256 1536 pass [2]
Notes:
[1] Kernels 2.6.23.4 - 2.6.23.16 and 2.6.24 - current with Herbert's patch
[2] Kernels 2.6.23.3 and before without Herbert's patch
Note that the first row has skb_headroom + skb_tailroom == 1664; the
remaining rows have skb_headroom + skb_tailroom == 1792.
>From these results, it looks like a data alignment issue. Herbert's
patch unfortunately just happened to change the alignment in a way that
made it break.
Tony
The following patch fixes the problem for me. Do we want to accept this
patch and call it a day or continue investigating the source of the problem?
Patch applies to 2.6.24.2, but doesn't apply to 2.6.25-rc. If everyone
agrees that this is the right solution, I will resubmit with a proper
subject line and description.
Tony
--- linux-2.6.24.2/include/net/sock.h.orig 2008-02-20 17:19:20.000000000 -0500
+++ linux-2.6.24.2/include/net/sock.h 2008-02-20 17:25:55.000000000 -0500
@@ -1236,8 +1236,10 @@ static inline struct sk_buff *sk_stream_
{
struct sk_buff *skb;
- /* The TCP header must be at least 32-bit aligned. */
- size = ALIGN(size, 4);
+ /* The TCP header must be at least 32-bit aligned, but some chipsets
+ * such as Broadcom BCM5701 require at least 16-byte alignment.
+ */
+ size = ALIGN(size, 16);
skb = alloc_skb_fclone(size + sk->sk_prot->max_header, gfp);
if (skb) {
From: Tony Battersby <[email protected]>
Date: Wed, 20 Feb 2008 18:04:09 -0500
> The following patch fixes the problem for me. Do we want to accept this
> patch and call it a day or continue investigating the source of the problem?
>
> Patch applies to 2.6.24.2, but doesn't apply to 2.6.25-rc. If everyone
> agrees that this is the right solution, I will resubmit with a proper
> subject line and description.
A chipset bug, if it even exists, should be worked around in the
driver for that hardware. We shouldn't make every other piece
of hardware in the world suffer too.
On Wed, 2008-02-20 at 15:08 -0800, David Miller wrote:
> From: Tony Battersby <[email protected]>
> Date: Wed, 20 Feb 2008 18:04:09 -0500
>
> > The following patch fixes the problem for me. Do we want to accept this
> > patch and call it a day or continue investigating the source of the problem?
> >
> > Patch applies to 2.6.24.2, but doesn't apply to 2.6.25-rc. If everyone
> > agrees that this is the right solution, I will resubmit with a proper
> > subject line and description.
>
> A chipset bug, if it even exists, should be worked around in the
> driver for that hardware. We shouldn't make every other piece
> of hardware in the world suffer too.
>
>
Yes, we should workaround this in the TG3 driver once we understand what
the problem is and how to workaround it. We are still looking through
the errata list to sort this out. It looks like it is the starting DMA
address of the TX buffer that is causing the problem.