From mboxrd@z Thu Jan 1 00:00:00 1970 From: TB Subject: Re: [PATCH] tcp_cubic: limit delayed_ack ratio to prevent divide error Date: Wed, 11 May 2011 10:49:01 -0400 Message-ID: <4DCAA1DD.6010609@techboom.com> References: <20110504113351.4643a0c9@nehalam> <16668.1304537481@localhost> <20110504123738.7bb4d1ee@nehalam> <20110504.124053.260068550.davem@davemloft.net> <20110504130456.425dee68@nehalam> <4DC41EB2.6070404@techboom.com> <20110506095359.57c4fb38@nehalam> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: "Brandeburg, Jesse" , David Miller , Sangtae Ha , Injong Rhee , "Valdis.Kletnieks@vt.edu" , "rdunlap@xenotime.net" , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" To: Stephen Hemminger Return-path: In-Reply-To: <20110506095359.57c4fb38@nehalam> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 11-05-06 12:53 PM, Stephen Hemminger wrote: > On Fri, 06 May 2011 12:15:46 -0400 > TB wrote: > >> -----BEGIN PGP SIGNED MESSAGE----- >> Hash: SHA1 >> >> On 11-05-04 04:53 PM, Brandeburg, Jesse wrote: >>> >>> >>> On Wed, 4 May 2011, Stephen Hemminger wrote: >>> >>>> TCP Cubic keeps a metric that estimates the amount of delayed >>>> acknowledgements to use in adjusting the window. If an abnormally >>>> large number of packets are acknowledged at once, then the update >>>> could wrap and reach zero. This kind of ACK could only >>>> happen when there was a large window and huge number of >>>> ACK's were lost. >>>> >>>> This patch limits the value of delayed ack ratio. The choice of 32 >>>> is just a conservative value since normally it should be range of >>>> 1 to 4 packets. >>>> >>>> Signed-off-by: Stephen Hemminger >>> >>> patch seems fine, but please credit the reporter (lkml@techboom.com) with >>> reporting the issue with logs, maybe even with Reported-by: and some kind >>> of reference to the panic message or the email thread in the text or >>> header? >> >> We're currently testing the patch on 6 production servers > > Thank you, is there some regularity to the failures previously? This is now being tested on about 50 servers and we just had another panic, on a server with 2.6.38.5 and this patch. [405542.454073] ------------[ cut here ]------------ [405542.454109] kernel BUG at net/ipv4/tcp_output.c:1006! [405542.454136] invalid opcode: 0000 [#1] [405542.454166] last sysfs file: /sys/devices/pci0000:00/0000:00:1f.2/host6/scsi_host/host6/proc_name [405542.454213] CPU 0 [405542.454220] Modules linked in: i2c_i801 evdev i2c_core button [last unloaded: scsi_wait_scan] [405542.454300] [405542.454320] Pid: 0, comm: swapper Not tainted 2.6.38.5 #8 / [405542.454379] RIP: 0010:[] [] tcp_fragment+0x22/0x29a [405542.454433] RSP: 0018:ffff8800bf403a30 EFLAGS: 00010202 [405542.454460] RAX: ffff88000cd35000 RBX: ffff88006b84f480 RCX: 0000000000000218 [405542.454504] RDX: 0000000000001708 RSI: ffff88006b84f480 RDI: ffff880008d6b200 [405542.454548] RBP: 0000000000001540 R08: 0000000000000002 R09: 000000001027984a [405542.454592] R10: ffff8800b915f428 R11: ffff880008d6b200 R12: ffff88006b84f4a8 [405542.454636] R13: 0000000000001708 R14: 0000000000000000 R15: ffff880008d6b200 [405542.454680] FS: 0000000000000000(0000) GS:ffff8800bf400000(0000) knlGS:0000000000000000 [405542.454726] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b [405542.454754] CR2: 00007f94055c7000 CR3: 000000083e0bd000 CR4: 00000000000006f0 [405542.454798] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [405542.454842] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 [405542.454886] Process swapper (pid: 0, threadinfo ffffffff8176c000, task ffffffff81777020) [405542.454931] Stack: [405542.454951] 0000000000000000 0000021808d6b798 00000002000005b4 ffff88006b84f480 [405542.455006] ffff880008d6b200 ffff88006b84f4a8 0000000000000015 0000000000000000 [405542.455061] ffff880008d6b300 ffffffff814df7a4 ffff8802a3965140 00000000000001a0 [405542.455115] Call Trace: [405542.455137] [405542.455162] [] ? tcp_mark_head_lost+0x13c/0x202 [405542.455192] [] ? tcp_ack+0xe98/0x1a89 [405542.455220] [] ? tcp_validate_incoming+0x69/0x290 [405542.455250] [] ? tcp_rcv_established+0x7aa/0xa13 [405542.455281] [] ? tcp_v4_do_rcv+0x1b2/0x382 [405542.455310] [] ? nf_iterate+0x40/0x78 [405542.455338] [] ? tcp_v4_rcv+0x484/0x797 [405542.455368] [] ? ip_local_deliver_finish+0xab/0x139 [405542.455398] [] ? __netif_receive_skb+0x31c/0x349 [405542.455428] [] ? netif_receive_skb+0x67/0x6d [405542.455457] [] ? napi_gro_receive+0x9d/0xab [405542.455485] [] ? napi_skb_finish+0x1c/0x31 [405542.455516] [] ? igb_poll+0x7d5/0xb2e [405542.455544] [] ? igb_poll+0x8bc/0xb2e [405542.455572] [] ? igb_msix_ring+0x6e/0x75 [405542.455602] [] ? handle_IRQ_event+0x51/0x119 [405542.455631] [] ? net_rx_action+0xa7/0x212 [405542.455661] [] ? __do_softirq+0xbe/0x184 [405542.455690] [] ? call_softirq+0x1c/0x28 [405542.455719] [] ? do_softirq+0x31/0x63 [405542.455746] [] ? irq_exit+0x36/0x78 [405542.455773] [] ? do_IRQ+0x98/0xae [405542.455802] [] ? ret_from_intr+0x0/0xe [405542.455829] [405542.455860] [] ? mwait_idle+0xb9/0xf3 [405542.455888] [] ? cpu_idle+0x57/0x8d [405542.455921] [] ? start_kernel+0x34e/0x35a [405542.455950] [] ? x86_64_start_kernel+0xf3/0xf9 [405542.455977] Code: f> [405542.456239] RIP [] tcp_fragment+0x22/0x29a [405542.456270] RSP [405542.456543] ---[ end trace 231aaa222f893065 ]--- [405542.456600] Kernel panic - not syncing: Fatal exception in interrupt [405542.456659] Pid: 0, comm: swapper Tainted: G D 2.6.38.5 #8 [405542.456719] Call Trace: [405542.456770] [] ? panic+0x9d/0x1a0 [405542.456863] [] ? ret_from_intr+0x0/0xe [405542.456923] [] ? kmsg_dump+0x46/0xec [405542.456981] [] ? oops_end+0x9f/0xac [405542.457039] [] ? do_invalid_op+0x85/0x8f [405542.457097] [] ? tcp_fragment+0x22/0x29a [405542.457156] [] ? tcp_fragment+0x1f9/0x29a [405542.457216] [] ? invalid_op+0x15/0x20 [405542.457276] [] ? tcp_fragment+0x22/0x29a [405542.457337] [] ? tcp_mark_head_lost+0x13c/0x202 [405542.457400] [] ? tcp_ack+0xe98/0x1a89 [405542.457461] [] ? tcp_validate_incoming+0x69/0x290 [405542.457524] [] ? tcp_rcv_established+0x7aa/0xa13 [405542.457586] [] ? tcp_v4_do_rcv+0x1b2/0x382 [405542.457645] [] ? nf_iterate+0x40/0x78 [405542.457703] [] ? tcp_v4_rcv+0x484/0x797 [405542.457761] [] ? ip_local_deliver_finish+0xab/0x139 [405542.457827] [] ? __netif_receive_skb+0x31c/0x349 [405542.457894] [] ? netif_receive_skb+0x67/0x6d [405542.457953] [] ? napi_gro_receive+0x9d/0xab [405542.458021] [] ? napi_skb_finish+0x1c/0x31 [405542.458080] [] ? igb_poll+0x7d5/0xb2e [405542.458138] [] ? igb_poll+0x8bc/0xb2e [405542.458196] [] ? igb_msix_ring+0x6e/0x75 [405542.458254] [] ? handle_IRQ_event+0x51/0x119 [405542.458313] [] ? net_rx_action+0xa7/0x212 [405542.458371] [] ? __do_softirq+0xbe/0x184 [405542.458430] [] ? call_softirq+0x1c/0x28 [405542.458488] [] ? do_softirq+0x31/0x63 [405542.458545] [] ? irq_exit+0x36/0x78 [405542.458602] [] ? do_IRQ+0x98/0xae [405542.458660] [] ? ret_from_intr+0x0/0xe [405542.458717] [] ? mwait_idle+0xb9/0xf3 [405542.458810] [] ? cpu_idle+0x57/0x8d [405542.458867] [] ? start_kernel+0x34e/0x35a [405542.458926] [] ? x86_64_start_kernel+0xf3/0xf9