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Groups > linux.kernel > #1740296 > unrolled thread
| Started by | Yuchung Cheng <ycheng@google.com> |
|---|---|
| First post | 2017-09-27 02:20 +0200 |
| Last post | 2017-09-29 01:40 +0200 |
| Articles | 4 — 2 participants |
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Re: [REGRESSION] Warning in tcp_fastretrans_alert() of net/ipv4/tcp_input.c Yuchung Cheng <ycheng@google.com> - 2017-09-27 02:20 +0200
Re: [REGRESSION] Warning in tcp_fastretrans_alert() of net/ipv4/tcp_input.c Yuchung Cheng <ycheng@google.com> - 2017-09-27 02:20 +0200
Re: [REGRESSION] Warning in tcp_fastretrans_alert() of net/ipv4/tcp_input.c Oleksandr Natalenko <oleksandr@natalenko.name> - 2017-09-28 10:20 +0200
Re: [REGRESSION] Warning in tcp_fastretrans_alert() of net/ipv4/tcp_input.c Yuchung Cheng <ycheng@google.com> - 2017-09-29 01:40 +0200
| From | Yuchung Cheng <ycheng@google.com> |
|---|---|
| Date | 2017-09-27 02:20 +0200 |
| Subject | Re: [REGRESSION] Warning in tcp_fastretrans_alert() of net/ipv4/tcp_input.c |
| Message-ID | <uu8f0-3mw-1@gated-at.bofh.it> |
On Tue, Sep 26, 2017 at 6:10 AM, Roman Gushchin <guro@fb.com> wrote: >> On Wed, Sep 20, 2017 at 6:46 PM, Roman Gushchin <guro@fb.com> wrote: >> > >> > > Hello. >> > > >> > > Since, IIRC, v4.11, there is some regression in TCP stack resulting in the >> > > warning shown below. Most of the time it is harmless, but rarely it just >> > > causes either freeze or (I believe, this is related too) panic in >> > > tcp_sacktag_walk() (because sk_buff passed to this function is NULL). >> > > Unfortunately, I still do not have proper stacktrace from panic, but will try >> > > to capture it if possible. >> > > >> > > Also, I have custom settings regarding TCP stack, shown below as well. ifb is >> > > used to shape traffic with tc. >> > > >> > > Please note this regression was already reported as BZ [1] and as a letter to >> > > ML [2], but got neither attention nor resolution. It is reproducible for (not >> > > only) me on my home router since v4.11 till v4.13.1 incl. >> > > >> > > Please advise on how to deal with it. I'll provide any additional info if >> > > necessary, also ready to test patches if any. >> > > >> > > Thanks. >> > > >> > > [1] https://bugzilla.kernel.org/show_bug.cgi?id=195835 >> > > [2] https://urldefense.proofpoint.com/v2/url?u=https-3A__www.spinics.net_lists_netdev_msg436158.html&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=jJYgtDM7QT-W-Fz_d29HYQ&m=MDDRfLG5DvdOeniMpaZDJI8ulKQ6PQ6OX_1YtRsiTMA&s=-n3dGZw-pQ95kMBUfq5G9nYZFcuWtbTDlYFkcvQPoKc&e= >> > >> > We're experiencing the same problems on some machines in our fleet. >> > Exactly the same symptoms: tcp_fastretrans_alert() warnings and >> > sometimes panics in tcp_sacktag_walk(). >> > >> > Here is an example of a backtrace with the panic log: > > Hi Yuchung! > >> do you still see the panics if you disable RACK? >> sysctl net.ipv4.tcp_recovery=0? > > No, we haven't seen any crash since that. I am out of ideas how RACK can potentially cause tcp_sacktag_walk to take an empty skb :-( Do you have stack trace or any hint on which call to tcp-sacktag_walk triggered the panic? internally at Google we never see that. > >> >> also have you experience any sack reneg? could you post the output of >> ' nstat |grep -i TCP' thanks > > hostname TcpActiveOpens 2289680 0.0 > hostname TcpPassiveOpens 3592758 0.0 > hostname TcpAttemptFails 746910 0.0 > hostname TcpEstabResets 154988 0.0 > hostname TcpInSegs 16258678255 0.0 > hostname TcpOutSegs 46967011611 0.0 > hostname TcpRetransSegs 13724310 0.0 > hostname TcpInErrs 2 0.0 > hostname TcpOutRsts 9418798 0.0 > hostname TcpExtEmbryonicRsts 2303 0.0 > hostname TcpExtPruneCalled 90192 0.0 > hostname TcpExtOfoPruned 57274 0.0 > hostname TcpExtOutOfWindowIcmps 3 0.0 > hostname TcpExtTW 1164705 0.0 > hostname TcpExtTWRecycled 2 0.0 > hostname TcpExtPAWSEstab 159 0.0 > hostname TcpExtDelayedACKs 209207209 0.0 > hostname TcpExtDelayedACKLocked 508571 0.0 > hostname TcpExtDelayedACKLost 1713248 0.0 > hostname TcpExtListenOverflows 625 0.0 > hostname TcpExtListenDrops 625 0.0 > hostname TcpExtTCPHPHits 9341188489 0.0 > hostname TcpExtTCPPureAcks 1434646465 0.0 > hostname TcpExtTCPHPAcks 5733614672 0.0 > hostname TcpExtTCPSackRecovery 3261698 0.0 > hostname TcpExtTCPSACKReneging 12203 0.0 > hostname TcpExtTCPSACKReorder 433189 0.0 > hostname TcpExtTCPTSReorder 22694 0.0 > hostname TcpExtTCPFullUndo 45092 0.0 > hostname TcpExtTCPPartialUndo 22016 0.0 > hostname TcpExtTCPLossUndo 2150040 0.0 > hostname TcpExtTCPLostRetransmit 60119 0.0 > hostname TcpExtTCPSackFailures 2626782 0.0 > hostname TcpExtTCPLossFailures 182999 0.0 > hostname TcpExtTCPFastRetrans 4334275 0.0 > hostname TcpExtTCPSlowStartRetrans 3453348 0.0 > hostname TcpExtTCPTimeouts 1070997 0.0 > hostname TcpExtTCPLossProbes 2633545 0.0 > hostname TcpExtTCPLossProbeRecovery 941647 0.0 > hostname TcpExtTCPSackRecoveryFail 336302 0.0 > hostname TcpExtTCPRcvCollapsed 461354 0.0 > hostname TcpExtTCPAbortOnData 349196 0.0 > hostname TcpExtTCPAbortOnClose 3395 0.0 > hostname TcpExtTCPAbortOnTimeout 51201 0.0 > hostname TcpExtTCPMemoryPressures 2 0.0 > hostname TcpExtTCPSpuriousRTOs 2120503 0.0 > hostname TcpExtTCPSackShifted 2613736 0.0 > hostname TcpExtTCPSackMerged 21358743 0.0 > hostname TcpExtTCPSackShiftFallback 8769387 0.0 > hostname TcpExtTCPBacklogDrop 5 0.0 > hostname TcpExtTCPRetransFail 843 0.0 > hostname TcpExtTCPRcvCoalesce 949068035 0.0 > hostname TcpExtTCPOFOQueue 470118 0.0 > hostname TcpExtTCPOFODrop 9915 0.0 > hostname TcpExtTCPOFOMerge 9 0.0 > hostname TcpExtTCPChallengeACK 90 0.0 > hostname TcpExtTCPSYNChallenge 3 0.0 > hostname TcpExtTCPFastOpenActive 2089 0.0 > hostname TcpExtTCPSpuriousRtxHostQueues 896596 0.0 > hostname TcpExtTCPAutoCorking 547386735 0.0 > hostname TcpExtTCPFromZeroWindowAdv 28757 0.0 > hostname TcpExtTCPToZeroWindowAdv 28761 0.0 > hostname TcpExtTCPWantZeroWindowAdv 322431 0.0 > hostname TcpExtTCPSynRetrans 3026 0.0 > hostname TcpExtTCPOrigDataSent 40976870977 0.0 > hostname TcpExtTCPHystartTrainDetect 453920 0.0 > hostname TcpExtTCPHystartTrainCwnd 11586273 0.0 > hostname TcpExtTCPHystartDelayDetect 10943 0.0 > hostname TcpExtTCPHystartDelayCwnd 763554 0.0 > hostname TcpExtTCPACKSkippedPAWS 30 0.0 > hostname TcpExtTCPACKSkippedSeq 218 0.0 > hostname TcpExtTCPWinProbe 2408 0.0 > hostname TcpExtTCPKeepAlive 213768 0.0 > hostname TcpExtTCPMTUPFail 69 0.0 > hostname TcpExtTCPMTUPSuccess 8811 0.0 > > Thanks!
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| From | Yuchung Cheng <ycheng@google.com> |
|---|---|
| Date | 2017-09-27 02:20 +0200 |
| Message-ID | <uu8f0-3mw-7@gated-at.bofh.it> |
| In reply to | #1740296 |
On Tue, Sep 26, 2017 at 5:12 PM, Yuchung Cheng <ycheng@google.com> wrote: > On Tue, Sep 26, 2017 at 6:10 AM, Roman Gushchin <guro@fb.com> wrote: >>> On Wed, Sep 20, 2017 at 6:46 PM, Roman Gushchin <guro@fb.com> wrote: >>> > >>> > > Hello. >>> > > >>> > > Since, IIRC, v4.11, there is some regression in TCP stack resulting in the >>> > > warning shown below. Most of the time it is harmless, but rarely it just >>> > > causes either freeze or (I believe, this is related too) panic in >>> > > tcp_sacktag_walk() (because sk_buff passed to this function is NULL). >>> > > Unfortunately, I still do not have proper stacktrace from panic, but will try >>> > > to capture it if possible. >>> > > >>> > > Also, I have custom settings regarding TCP stack, shown below as well. ifb is >>> > > used to shape traffic with tc. >>> > > >>> > > Please note this regression was already reported as BZ [1] and as a letter to >>> > > ML [2], but got neither attention nor resolution. It is reproducible for (not >>> > > only) me on my home router since v4.11 till v4.13.1 incl. >>> > > >>> > > Please advise on how to deal with it. I'll provide any additional info if >>> > > necessary, also ready to test patches if any. >>> > > >>> > > Thanks. >>> > > >>> > > [1] https://bugzilla.kernel.org/show_bug.cgi?id=195835 >>> > > [2] https://urldefense.proofpoint.com/v2/url?u=https-3A__www.spinics.net_lists_netdev_msg436158.html&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=jJYgtDM7QT-W-Fz_d29HYQ&m=MDDRfLG5DvdOeniMpaZDJI8ulKQ6PQ6OX_1YtRsiTMA&s=-n3dGZw-pQ95kMBUfq5G9nYZFcuWtbTDlYFkcvQPoKc&e= >>> > >>> > We're experiencing the same problems on some machines in our fleet. >>> > Exactly the same symptoms: tcp_fastretrans_alert() warnings and >>> > sometimes panics in tcp_sacktag_walk(). >>> > >>> > Here is an example of a backtrace with the panic log: >> >> Hi Yuchung! >> >>> do you still see the panics if you disable RACK? >>> sysctl net.ipv4.tcp_recovery=0? >> >> No, we haven't seen any crash since that. > I am out of ideas how RACK can potentially cause tcp_sacktag_walk to > take an empty skb :-( Do you have stack trace or any hint on which call > to tcp-sacktag_walk triggered the panic? internally at Google we never > see that. hmm something just struck me: could you try sysctl net.ipv4.tcp_recovery=1 net.ipv4.tcp_retrans_collapse=0 and see if kernel still panics on sack processing? > > >> >>> >>> also have you experience any sack reneg? could you post the output of >>> ' nstat |grep -i TCP' thanks >> >> hostname TcpActiveOpens 2289680 0.0 >> hostname TcpPassiveOpens 3592758 0.0 >> hostname TcpAttemptFails 746910 0.0 >> hostname TcpEstabResets 154988 0.0 >> hostname TcpInSegs 16258678255 0.0 >> hostname TcpOutSegs 46967011611 0.0 >> hostname TcpRetransSegs 13724310 0.0 >> hostname TcpInErrs 2 0.0 >> hostname TcpOutRsts 9418798 0.0 >> hostname TcpExtEmbryonicRsts 2303 0.0 >> hostname TcpExtPruneCalled 90192 0.0 >> hostname TcpExtOfoPruned 57274 0.0 >> hostname TcpExtOutOfWindowIcmps 3 0.0 >> hostname TcpExtTW 1164705 0.0 >> hostname TcpExtTWRecycled 2 0.0 >> hostname TcpExtPAWSEstab 159 0.0 >> hostname TcpExtDelayedACKs 209207209 0.0 >> hostname TcpExtDelayedACKLocked 508571 0.0 >> hostname TcpExtDelayedACKLost 1713248 0.0 >> hostname TcpExtListenOverflows 625 0.0 >> hostname TcpExtListenDrops 625 0.0 >> hostname TcpExtTCPHPHits 9341188489 0.0 >> hostname TcpExtTCPPureAcks 1434646465 0.0 >> hostname TcpExtTCPHPAcks 5733614672 0.0 >> hostname TcpExtTCPSackRecovery 3261698 0.0 >> hostname TcpExtTCPSACKReneging 12203 0.0 >> hostname TcpExtTCPSACKReorder 433189 0.0 >> hostname TcpExtTCPTSReorder 22694 0.0 >> hostname TcpExtTCPFullUndo 45092 0.0 >> hostname TcpExtTCPPartialUndo 22016 0.0 >> hostname TcpExtTCPLossUndo 2150040 0.0 >> hostname TcpExtTCPLostRetransmit 60119 0.0 >> hostname TcpExtTCPSackFailures 2626782 0.0 >> hostname TcpExtTCPLossFailures 182999 0.0 >> hostname TcpExtTCPFastRetrans 4334275 0.0 >> hostname TcpExtTCPSlowStartRetrans 3453348 0.0 >> hostname TcpExtTCPTimeouts 1070997 0.0 >> hostname TcpExtTCPLossProbes 2633545 0.0 >> hostname TcpExtTCPLossProbeRecovery 941647 0.0 >> hostname TcpExtTCPSackRecoveryFail 336302 0.0 >> hostname TcpExtTCPRcvCollapsed 461354 0.0 >> hostname TcpExtTCPAbortOnData 349196 0.0 >> hostname TcpExtTCPAbortOnClose 3395 0.0 >> hostname TcpExtTCPAbortOnTimeout 51201 0.0 >> hostname TcpExtTCPMemoryPressures 2 0.0 >> hostname TcpExtTCPSpuriousRTOs 2120503 0.0 >> hostname TcpExtTCPSackShifted 2613736 0.0 >> hostname TcpExtTCPSackMerged 21358743 0.0 >> hostname TcpExtTCPSackShiftFallback 8769387 0.0 >> hostname TcpExtTCPBacklogDrop 5 0.0 >> hostname TcpExtTCPRetransFail 843 0.0 >> hostname TcpExtTCPRcvCoalesce 949068035 0.0 >> hostname TcpExtTCPOFOQueue 470118 0.0 >> hostname TcpExtTCPOFODrop 9915 0.0 >> hostname TcpExtTCPOFOMerge 9 0.0 >> hostname TcpExtTCPChallengeACK 90 0.0 >> hostname TcpExtTCPSYNChallenge 3 0.0 >> hostname TcpExtTCPFastOpenActive 2089 0.0 >> hostname TcpExtTCPSpuriousRtxHostQueues 896596 0.0 >> hostname TcpExtTCPAutoCorking 547386735 0.0 >> hostname TcpExtTCPFromZeroWindowAdv 28757 0.0 >> hostname TcpExtTCPToZeroWindowAdv 28761 0.0 >> hostname TcpExtTCPWantZeroWindowAdv 322431 0.0 >> hostname TcpExtTCPSynRetrans 3026 0.0 >> hostname TcpExtTCPOrigDataSent 40976870977 0.0 >> hostname TcpExtTCPHystartTrainDetect 453920 0.0 >> hostname TcpExtTCPHystartTrainCwnd 11586273 0.0 >> hostname TcpExtTCPHystartDelayDetect 10943 0.0 >> hostname TcpExtTCPHystartDelayCwnd 763554 0.0 >> hostname TcpExtTCPACKSkippedPAWS 30 0.0 >> hostname TcpExtTCPACKSkippedSeq 218 0.0 >> hostname TcpExtTCPWinProbe 2408 0.0 >> hostname TcpExtTCPKeepAlive 213768 0.0 >> hostname TcpExtTCPMTUPFail 69 0.0 >> hostname TcpExtTCPMTUPSuccess 8811 0.0 >> >> Thanks!
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| From | Oleksandr Natalenko <oleksandr@natalenko.name> |
|---|---|
| Date | 2017-09-28 10:20 +0200 |
| Message-ID | <uuCd4-6xg-19@gated-at.bofh.it> |
| In reply to | #1740297 |
Hi. Won't tell about panic in tcp_sacktag_walk() since I cannot trigger it intentionally, but setting net.ipv4.tcp_retrans_collapse to 0 *does not* fix warning in tcp_fastretrans_alert() for me. On středa 27. září 2017 2:18:32 CEST Yuchung Cheng wrote: > On Tue, Sep 26, 2017 at 5:12 PM, Yuchung Cheng <ycheng@google.com> wrote: > > On Tue, Sep 26, 2017 at 6:10 AM, Roman Gushchin <guro@fb.com> wrote: > >>> On Wed, Sep 20, 2017 at 6:46 PM, Roman Gushchin <guro@fb.com> wrote: > >>> > > Hello. > >>> > > > >>> > > Since, IIRC, v4.11, there is some regression in TCP stack resulting > >>> > > in the > >>> > > warning shown below. Most of the time it is harmless, but rarely it > >>> > > just > >>> > > causes either freeze or (I believe, this is related too) panic in > >>> > > tcp_sacktag_walk() (because sk_buff passed to this function is > >>> > > NULL). > >>> > > Unfortunately, I still do not have proper stacktrace from panic, but > >>> > > will try to capture it if possible. > >>> > > > >>> > > Also, I have custom settings regarding TCP stack, shown below as > >>> > > well. ifb is used to shape traffic with tc. > >>> > > > >>> > > Please note this regression was already reported as BZ [1] and as a > >>> > > letter to ML [2], but got neither attention nor resolution. It is > >>> > > reproducible for (not only) me on my home router since v4.11 till > >>> > > v4.13.1 incl. > >>> > > > >>> > > Please advise on how to deal with it. I'll provide any additional > >>> > > info if > >>> > > necessary, also ready to test patches if any. > >>> > > > >>> > > Thanks. > >>> > > > >>> > > [1] https://bugzilla.kernel.org/show_bug.cgi?id=195835 > >>> > > [2] > >>> > > https://urldefense.proofpoint.com/v2/url?u=https-3A__www.spinics.ne > >>> > > t_lists_netdev_msg436158.html&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=jJ > >>> > > YgtDM7QT-W-Fz_d29HYQ&m=MDDRfLG5DvdOeniMpaZDJI8ulKQ6PQ6OX_1YtRsiTMA&s > >>> > > =-n3dGZw-pQ95kMBUfq5G9nYZFcuWtbTDlYFkcvQPoKc&e=>>> > > >>> > We're experiencing the same problems on some machines in our fleet. > >>> > Exactly the same symptoms: tcp_fastretrans_alert() warnings and > >>> > sometimes panics in tcp_sacktag_walk(). > >> > >>> > Here is an example of a backtrace with the panic log: > >> Hi Yuchung! > >> > >>> do you still see the panics if you disable RACK? > >>> sysctl net.ipv4.tcp_recovery=0? > >> > >> No, we haven't seen any crash since that. > > > > I am out of ideas how RACK can potentially cause tcp_sacktag_walk to > > take an empty skb :-( Do you have stack trace or any hint on which call > > to tcp-sacktag_walk triggered the panic? internally at Google we never > > see that. > > hmm something just struck me: could you try > sysctl net.ipv4.tcp_recovery=1 net.ipv4.tcp_retrans_collapse=0 > and see if kernel still panics on sack processing? > > >>> also have you experience any sack reneg? could you post the output of > >>> ' nstat |grep -i TCP' thanks > >> > >> hostname TcpActiveOpens 2289680 0.0 > >> hostname TcpPassiveOpens 3592758 0.0 > >> hostname TcpAttemptFails 746910 0.0 > >> hostname TcpEstabResets 154988 0.0 > >> hostname TcpInSegs 16258678255 0.0 > >> hostname TcpOutSegs 46967011611 0.0 > >> hostname TcpRetransSegs 13724310 0.0 > >> hostname TcpInErrs 2 0.0 > >> hostname TcpOutRsts 9418798 0.0 > >> hostname TcpExtEmbryonicRsts 2303 0.0 > >> hostname TcpExtPruneCalled 90192 0.0 > >> hostname TcpExtOfoPruned 57274 0.0 > >> hostname TcpExtOutOfWindowIcmps 3 0.0 > >> hostname TcpExtTW 1164705 0.0 > >> hostname TcpExtTWRecycled 2 0.0 > >> hostname TcpExtPAWSEstab 159 0.0 > >> hostname TcpExtDelayedACKs 209207209 0.0 > >> hostname TcpExtDelayedACKLocked 508571 0.0 > >> hostname TcpExtDelayedACKLost 1713248 0.0 > >> hostname TcpExtListenOverflows 625 0.0 > >> hostname TcpExtListenDrops 625 0.0 > >> hostname TcpExtTCPHPHits 9341188489 0.0 > >> hostname TcpExtTCPPureAcks 1434646465 0.0 > >> hostname TcpExtTCPHPAcks 5733614672 0.0 > >> hostname TcpExtTCPSackRecovery 3261698 0.0 > >> hostname TcpExtTCPSACKReneging 12203 0.0 > >> hostname TcpExtTCPSACKReorder 433189 0.0 > >> hostname TcpExtTCPTSReorder 22694 0.0 > >> hostname TcpExtTCPFullUndo 45092 0.0 > >> hostname TcpExtTCPPartialUndo 22016 0.0 > >> hostname TcpExtTCPLossUndo 2150040 0.0 > >> hostname TcpExtTCPLostRetransmit 60119 0.0 > >> hostname TcpExtTCPSackFailures 2626782 0.0 > >> hostname TcpExtTCPLossFailures 182999 0.0 > >> hostname TcpExtTCPFastRetrans 4334275 0.0 > >> hostname TcpExtTCPSlowStartRetrans 3453348 0.0 > >> hostname TcpExtTCPTimeouts 1070997 0.0 > >> hostname TcpExtTCPLossProbes 2633545 0.0 > >> hostname TcpExtTCPLossProbeRecovery 941647 0.0 > >> hostname TcpExtTCPSackRecoveryFail 336302 0.0 > >> hostname TcpExtTCPRcvCollapsed 461354 0.0 > >> hostname TcpExtTCPAbortOnData 349196 0.0 > >> hostname TcpExtTCPAbortOnClose 3395 0.0 > >> hostname TcpExtTCPAbortOnTimeout 51201 0.0 > >> hostname TcpExtTCPMemoryPressures 2 0.0 > >> hostname TcpExtTCPSpuriousRTOs 2120503 0.0 > >> hostname TcpExtTCPSackShifted 2613736 0.0 > >> hostname TcpExtTCPSackMerged 21358743 0.0 > >> hostname TcpExtTCPSackShiftFallback 8769387 0.0 > >> hostname TcpExtTCPBacklogDrop 5 0.0 > >> hostname TcpExtTCPRetransFail 843 0.0 > >> hostname TcpExtTCPRcvCoalesce 949068035 0.0 > >> hostname TcpExtTCPOFOQueue 470118 0.0 > >> hostname TcpExtTCPOFODrop 9915 0.0 > >> hostname TcpExtTCPOFOMerge 9 0.0 > >> hostname TcpExtTCPChallengeACK 90 0.0 > >> hostname TcpExtTCPSYNChallenge 3 0.0 > >> hostname TcpExtTCPFastOpenActive 2089 0.0 > >> hostname TcpExtTCPSpuriousRtxHostQueues 896596 0.0 > >> hostname TcpExtTCPAutoCorking 547386735 0.0 > >> hostname TcpExtTCPFromZeroWindowAdv 28757 0.0 > >> hostname TcpExtTCPToZeroWindowAdv 28761 0.0 > >> hostname TcpExtTCPWantZeroWindowAdv 322431 0.0 > >> hostname TcpExtTCPSynRetrans 3026 0.0 > >> hostname TcpExtTCPOrigDataSent 40976870977 0.0 > >> hostname TcpExtTCPHystartTrainDetect 453920 0.0 > >> hostname TcpExtTCPHystartTrainCwnd 11586273 0.0 > >> hostname TcpExtTCPHystartDelayDetect 10943 0.0 > >> hostname TcpExtTCPHystartDelayCwnd 763554 0.0 > >> hostname TcpExtTCPACKSkippedPAWS 30 0.0 > >> hostname TcpExtTCPACKSkippedSeq 218 0.0 > >> hostname TcpExtTCPWinProbe 2408 0.0 > >> hostname TcpExtTCPKeepAlive 213768 0.0 > >> hostname TcpExtTCPMTUPFail 69 0.0 > >> hostname TcpExtTCPMTUPSuccess 8811 0.0 > >> > >> Thanks!
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| From | Yuchung Cheng <ycheng@google.com> |
|---|---|
| Date | 2017-09-29 01:40 +0200 |
| Message-ID | <uuQzo-6Ul-13@gated-at.bofh.it> |
| In reply to | #1741268 |
On Thu, Sep 28, 2017 at 1:14 AM, Oleksandr Natalenko <oleksandr@natalenko.name> wrote: > Hi. > > Won't tell about panic in tcp_sacktag_walk() since I cannot trigger it > intentionally, but setting net.ipv4.tcp_retrans_collapse to 0 *does not* fix > warning in tcp_fastretrans_alert() for me. Hi Oleksandr: no retrans_collapse should not matter for that warning in tcp_fstretrans_alert(). the warning as I explained earlier is likely false. Neal and I are more concerned the panic in tcp_sacktag_walk. This is just a blind shot but thx for retrying. We can submit a one-liner to remove the fast retrans warning but want to nail the bigger issue first. > > On středa 27. září 2017 2:18:32 CEST Yuchung Cheng wrote: >> On Tue, Sep 26, 2017 at 5:12 PM, Yuchung Cheng <ycheng@google.com> wrote: >> > On Tue, Sep 26, 2017 at 6:10 AM, Roman Gushchin <guro@fb.com> wrote: >> >>> On Wed, Sep 20, 2017 at 6:46 PM, Roman Gushchin <guro@fb.com> wrote: >> >>> > > Hello. >> >>> > > >> >>> > > Since, IIRC, v4.11, there is some regression in TCP stack resulting >> >>> > > in the >> >>> > > warning shown below. Most of the time it is harmless, but rarely it >> >>> > > just >> >>> > > causes either freeze or (I believe, this is related too) panic in >> >>> > > tcp_sacktag_walk() (because sk_buff passed to this function is >> >>> > > NULL). >> >>> > > Unfortunately, I still do not have proper stacktrace from panic, but >> >>> > > will try to capture it if possible. >> >>> > > >> >>> > > Also, I have custom settings regarding TCP stack, shown below as >> >>> > > well. ifb is used to shape traffic with tc. >> >>> > > >> >>> > > Please note this regression was already reported as BZ [1] and as a >> >>> > > letter to ML [2], but got neither attention nor resolution. It is >> >>> > > reproducible for (not only) me on my home router since v4.11 till >> >>> > > v4.13.1 incl. >> >>> > > >> >>> > > Please advise on how to deal with it. I'll provide any additional >> >>> > > info if >> >>> > > necessary, also ready to test patches if any. >> >>> > > >> >>> > > Thanks. >> >>> > > >> >>> > > [1] https://bugzilla.kernel.org/show_bug.cgi?id=195835 >> >>> > > [2] >> >>> > > https://urldefense.proofpoint.com/v2/url?u=https-3A__www.spinics.ne >> >>> > > t_lists_netdev_msg436158.html&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=jJ >> >>> > > YgtDM7QT-W-Fz_d29HYQ&m=MDDRfLG5DvdOeniMpaZDJI8ulKQ6PQ6OX_1YtRsiTMA&s >> >>> > > =-n3dGZw-pQ95kMBUfq5G9nYZFcuWtbTDlYFkcvQPoKc&e=>>> > >> >>> > We're experiencing the same problems on some machines in our fleet. >> >>> > Exactly the same symptoms: tcp_fastretrans_alert() warnings and >> >>> > sometimes panics in tcp_sacktag_walk(). >> >> >> >>> > Here is an example of a backtrace with the panic log: >> >> Hi Yuchung! >> >> >> >>> do you still see the panics if you disable RACK? >> >>> sysctl net.ipv4.tcp_recovery=0? >> >> >> >> No, we haven't seen any crash since that. >> > >> > I am out of ideas how RACK can potentially cause tcp_sacktag_walk to >> > take an empty skb :-( Do you have stack trace or any hint on which call >> > to tcp-sacktag_walk triggered the panic? internally at Google we never >> > see that. >> >> hmm something just struck me: could you try >> sysctl net.ipv4.tcp_recovery=1 net.ipv4.tcp_retrans_collapse=0 >> and see if kernel still panics on sack processing? >> >> >>> also have you experience any sack reneg? could you post the output of >> >>> ' nstat |grep -i TCP' thanks >> >> >> >> hostname TcpActiveOpens 2289680 0. 0 >> >> hostname TcpPassiveOpens 3592758 0. 0 >> >> hostname TcpAttemptFails 746910 0. 0 >> >> hostname TcpEstabResets 154988 0. 0 >> >> hostname TcpInSegs 16258678255 0. 0 >> >> hostname TcpOutSegs 46967011611 0. 0 >> >> hostname TcpRetransSegs 13724310 0. 0 >> >> hostname TcpInErrs 2 0. 0 >> >> hostname TcpOutRsts 9418798 0. 0 >> >> hostname TcpExtEmbryonicRsts 2303 0. 0 >> >> hostname TcpExtPruneCalled 90192 0. 0 >> >> hostname TcpExtOfoPruned 57274 0. 0 >> >> hostname TcpExtOutOfWindowIcmps 3 0. 0 >> >> hostname TcpExtTW 1164705 0. 0 >> >> hostname TcpExtTWRecycled 2 0. 0 >> >> hostname TcpExtPAWSEstab 159 0. 0 >> >> hostname TcpExtDelayedACKs 209207209 0. 0 >> >> hostname TcpExtDelayedACKLocked 508571 0. 0 >> >> hostname TcpExtDelayedACKLost 1713248 0. 0 >> >> hostname TcpExtListenOverflows 625 0. 0 >> >> hostname TcpExtListenDrops 625 0. 0 >> >> hostname TcpExtTCPHPHits 9341188489 0. 0 >> >> hostname TcpExtTCPPureAcks 1434646465 0. 0 >> >> hostname TcpExtTCPHPAcks 5733614672 0. 0 >> >> hostname TcpExtTCPSackRecovery 3261698 0. 0 >> >> hostname TcpExtTCPSACKReneging 12203 0. 0 >> >> hostname TcpExtTCPSACKReorder 433189 0. 0 >> >> hostname TcpExtTCPTSReorder 22694 0. 0 >> >> hostname TcpExtTCPFullUndo 45092 0. 0 >> >> hostname TcpExtTCPPartialUndo 22016 0. 0 >> >> hostname TcpExtTCPLossUndo 2150040 0. 0 >> >> hostname TcpExtTCPLostRetransmit 60119 0. 0 >> >> hostname TcpExtTCPSackFailures 2626782 0. 0 >> >> hostname TcpExtTCPLossFailures 182999 0. 0 >> >> hostname TcpExtTCPFastRetrans 4334275 0. 0 >> >> hostname TcpExtTCPSlowStartRetrans 3453348 0. 0 >> >> hostname TcpExtTCPTimeouts 1070997 0. 0 >> >> hostname TcpExtTCPLossProbes 2633545 0. 0 >> >> hostname TcpExtTCPLossProbeRecovery 941647 0. 0 >> >> hostname TcpExtTCPSackRecoveryFail 336302 0. 0 >> >> hostname TcpExtTCPRcvCollapsed 461354 0. 0 >> >> hostname TcpExtTCPAbortOnData 349196 0. 0 >> >> hostname TcpExtTCPAbortOnClose 3395 0. 0 >> >> hostname TcpExtTCPAbortOnTimeout 51201 0. 0 >> >> hostname TcpExtTCPMemoryPressures 2 0. 0 >> >> hostname TcpExtTCPSpuriousRTOs 2120503 0. 0 >> >> hostname TcpExtTCPSackShifted 2613736 0. 0 >> >> hostname TcpExtTCPSackMerged 21358743 0. 0 >> >> hostname TcpExtTCPSackShiftFallback 8769387 0. 0 >> >> hostname TcpExtTCPBacklogDrop 5 0. 0 >> >> hostname TcpExtTCPRetransFail 843 0. 0 >> >> hostname TcpExtTCPRcvCoalesce 949068035 0. 0 >> >> hostname TcpExtTCPOFOQueue 470118 0. 0 >> >> hostname TcpExtTCPOFODrop 9915 0. 0 >> >> hostname TcpExtTCPOFOMerge 9 0. 0 >> >> hostname TcpExtTCPChallengeACK 90 0. 0 >> >> hostname TcpExtTCPSYNChallenge 3 0. 0 >> >> hostname TcpExtTCPFastOpenActive 2089 0. 0 >> >> hostname TcpExtTCPSpuriousRtxHostQueues 896596 0. 0 >> >> hostname TcpExtTCPAutoCorking 547386735 0. 0 >> >> hostname TcpExtTCPFromZeroWindowAdv 28757 0. 0 >> >> hostname TcpExtTCPToZeroWindowAdv 28761 0. 0 >> >> hostname TcpExtTCPWantZeroWindowAdv 322431 0. 0 >> >> hostname TcpExtTCPSynRetrans 3026 0. 0 >> >> hostname TcpExtTCPOrigDataSent 40976870977 0. 0 >> >> hostname TcpExtTCPHystartTrainDetect 453920 0. 0 >> >> hostname TcpExtTCPHystartTrainCwnd 11586273 0. 0 >> >> hostname TcpExtTCPHystartDelayDetect 10943 0. 0 >> >> hostname TcpExtTCPHystartDelayCwnd 763554 0. 0 >> >> hostname TcpExtTCPACKSkippedPAWS 30 0. 0 >> >> hostname TcpExtTCPACKSkippedSeq 218 0. 0 >> >> hostname TcpExtTCPWinProbe 2408 0. 0 >> >> hostname TcpExtTCPKeepAlive 213768 0. 0 >> >> hostname TcpExtTCPMTUPFail 69 0. 0 >> >> hostname TcpExtTCPMTUPSuccess 8811 0. 0 >> >> >> >> Thanks! > >
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