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Date: Fri, 10 Feb 2012 19:05:49 -0500 From: sridhar basam <sri@...am.org> To: Jim Schutt <jaschut@...dia.gov> Cc: ceph-devel@...r.kernel.org, netdev@...r.kernel.org Subject: Re: [RFC PATCH 0/6] Understanding delays due to throttling under very heavy write load On Fri, Feb 10, 2012 at 6:09 PM, Jim Schutt <jaschut@...dia.gov> wrote: > > [ added Cc:netdev > See http://www.spinics.net/lists/ceph-devel/msg04804.html > for the start of the thread. > -- Jim > ] > > > On 02/10/2012 10:13 AM, sridhar basam wrote: >> >> On Fri, Feb 10, 2012 at 10:32 AM, Jim Schutt<jaschut@...dia.gov> wrote: >>> >>> On 02/09/2012 06:26 PM, sridhar basam wrote: >>>> >>>> >>>> Do you mind capturing to a pcap file and providing that. Makes it >>>> easier to analyse things. If not, i understand. If you can make do the >>>> capture on both ends, do it with a snaplen of 68 so that you get all >>>> of the headers and there shouldn't be too much payload information in >>>> the file. >>> >>> >>> >>> I've got a pcap file for this run for this client, with snaplen 128 >>> (I thought I might need to look for ceph message headers). It's 13 MB >>> compressed. How shall I get it to you? >>> >> >> Can i grab it off some webserver you control? Or you can temporarily >> drop it into docs.google.com and add accesss from my email account? > > > I tabled this for the moment while I worked on collecting > packet traces from both ends. But you'll probably want > to see the pcap files for what I'm about to show. Also, > I think I need to add netdev to this discussion ... > > >> >>> In the meantime, I'll try to capture this from both sides. > > > Here's another example, captured from both sides, with > TSO/GSO/GRO all off, snaplen 68. > > This was captured from the client side. Same pattern, in > that the client sends many retransmits over a period of > a couple minutes. It's different in that the client > seems to give up and reconnect ... > > 11:57:35.984024 IP 172.17.131.32.6807 > 172.17.135.4.57589: Flags [.], ack > 18109890, win 5792, options [nop,nop,TS[|tcp]> > 11:57:35.984032 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18112786:18114234, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:35.984038 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18114234:18115682, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:35.984120 IP 172.17.131.32.6807 > 172.17.135.4.57589: Flags [.], ack > 18112786, win 5792, options [nop,nop,TS[|tcp]> > 11:57:35.984129 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18115682:18117130, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:35.984135 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18117130:18118578, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:35.984143 IP 172.17.131.32.6807 > 172.17.135.4.57589: Flags [.], ack > 18115682, win 5792, options [nop,nop,TS[|tcp]> > 11:57:35.984148 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18118578:18120026, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:35.984153 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:35.984270 IP 172.17.131.32.6807 > 172.17.135.4.57589: Flags [.], ack > 18118578, win 5792, options [nop,nop,TS[|tcp]> > 11:57:35.984278 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18121474:18122922, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:35.984283 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18122922:18124370, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:35.984420 IP 172.17.131.32.6807 > 172.17.135.4.57589: Flags [.], ack > 18120026, win 5792, options [nop,nop,TS[|tcp]> > 11:57:35.984428 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18124370:18125818, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:36.184945 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:36.587936 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:37.393937 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:39.003937 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:42.227933 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:48.675931 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:58:01.555935 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:58:27.347945 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:59:18.867935 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 12:00:22.673029 IP 172.17.131.32.6807 > 172.17.135.4.57589: Flags [P.], seq > 863:1036, ack 18120026, win 5792, options [nop,nop,TS[|tcp]> > 12:00:22.712933 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], ack > 1036, win 19832, options [nop,nop,TS[|tcp]> > 12:01:02.035951 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 1036, win 19832, options [nop,nop,TS[|tcp]> > 12:03:02.355941 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 1036, win 19832, options [nop,nop,TS[|tcp]> > 12:05:02.675947 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 1036, win 19832, options [nop,nop,TS[|tcp]> > 12:07:02.995943 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 1036, win 19832, options [nop,nop,TS[|tcp]> > 12:09:03.315942 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 1036, win 19832, options [nop,nop,TS[|tcp]> > 12:11:03.635948 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 1036, win 19832, options [nop,nop,TS[|tcp]> > 12:13:03.961655 IP 172.17.135.4.57628 > 172.17.131.32.6807: Flags [S], seq > 1551304795, win 14600, options [mss 1460,[|tcp]> > 12:13:03.961722 IP 172.17.131.32.6807 > 172.17.135.4.57628: Flags [S.], seq > 2095554319, ack 1551304796, win 14480, options [mss 1460,[|tcp]> > 12:13:03.961732 IP 172.17.135.4.57628 > 172.17.131.32.6807: Flags [.], ack > 1, win 14600, options [nop,nop,TS[|tcp]> > 12:13:03.961822 IP 172.17.135.4.57628 > 172.17.131.32.6807: Flags [P.], seq > 1:201, ack 1, win 14600, options [nop,nop,TS[|tcp]> > 12:13:03.961874 IP 172.17.131.32.6807 > 172.17.135.4.57628: Flags [.], ack > 201, win 15544, options [nop,nop,TS[|tcp]> > 12:13:03.962070 IP 172.17.131.32.6807 > 172.17.135.4.57628: Flags [P.], seq > 1:10, ack 201, win 15544, options [nop,nop,TS[|tcp]> > 12:13:03.962077 IP 172.17.135.4.57628 > 172.17.131.32.6807: Flags [.], ack > 10, win 14600, options [nop,nop,TS[|tcp]> > 12:13:03.962370 IP 172.17.131.32.6807 > 172.17.135.4.57628: Flags [P.], seq > 10:282, ack 201, win 15544, options [nop,nop,TS[|tcp]> > 12:13:03.962377 IP 172.17.135.4.57628 > 172.17.131.32.6807: Flags [.], ack > 282, win 15544, options [nop,nop,TS[|tcp]> > 12:13:03.962819 IP 172.17.131.32.6807 > 172.17.135.4.57589: Flags [F.], seq > 1036, ack 18120026, win 5792, options [nop,nop,TS[|tcp]> > 12:13:03.962828 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [R], seq > 2449506432, win 0, length 0 > > Here's the same thing, captured from the server side: > > 11:57:36.012908 IP 172.17.131.32.6807 > 172.17.135.4.57589: Flags [.], ack > 18109890, win 5792, options [nop,nop,TS[|tcp]> > 11:57:36.012967 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18109890:18111338, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:36.012977 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18111338:18112786, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:36.013020 IP 172.17.131.32.6807 > 172.17.135.4.57589: Flags [.], ack > 18112786, win 5792, options [nop,nop,TS[|tcp]> > 11:57:36.013036 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18112786:18114234, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:36.013039 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18114234:18115682, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:36.013041 IP 172.17.131.32.6807 > 172.17.135.4.57589: Flags [.], ack > 18115682, win 5792, options [nop,nop,TS[|tcp]> > 11:57:36.013123 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18115682:18117130, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:36.013129 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18117130:18118578, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:36.013155 IP 172.17.131.32.6807 > 172.17.135.4.57589: Flags [.], ack > 18118578, win 5792, options [nop,nop,TS[|tcp]> > 11:57:36.013163 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18118578:18120026, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:36.013171 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:36.013261 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18121474:18122922, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:36.013281 IP 172.17.131.32.6807 > 172.17.135.4.57589: Flags [.], ack > 18120026, win 5792, options [nop,nop,TS[|tcp]> > 11:57:36.013288 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18122922:18124370, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:36.013410 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18124370:18125818, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:36.213941 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:36.617001 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:37.422996 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:39.033018 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:42.257206 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:57:48.705321 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:58:01.585648 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:58:27.378231 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 11:59:18.899063 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 863, win 18760, options [nop,nop,TS[|tcp]> > 12:00:22.704018 IP 172.17.131.32.6807 > 172.17.135.4.57589: Flags [P.], seq > 863:1036, ack 18120026, win 5792, options [nop,nop,TS[|tcp]> > 12:00:22.744053 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], ack > 1036, win 19832, options [nop,nop,TS[|tcp]> > 12:01:02.067040 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 1036, win 19832, options [nop,nop,TS[|tcp]> > 12:03:02.386981 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 1036, win 19832, options [nop,nop,TS[|tcp]> > 12:05:02.705227 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 1036, win 19832, options [nop,nop,TS[|tcp]> > 12:07:03.021427 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 1036, win 19832, options [nop,nop,TS[|tcp]> > 12:09:03.332661 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 1036, win 19832, options [nop,nop,TS[|tcp]> > 12:11:03.642409 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [.], seq > 18120026:18121474, ack 1036, win 19832, options [nop,nop,TS[|tcp]> > 12:13:03.963373 IP 172.17.135.4.57628 > 172.17.131.32.6807: Flags [S], seq > 1551304795, win 14600, options [mss 1460,[|tcp]> > 12:13:03.963389 IP 172.17.131.32.6807 > 172.17.135.4.57628: Flags [S.], seq > 2095554319, ack 1551304796, win 14480, options [mss 1460,[|tcp]> > 12:13:03.963446 IP 172.17.135.4.57628 > 172.17.131.32.6807: Flags [.], ack > 1, win 14600, options [nop,nop,TS[|tcp]> > 12:13:03.963540 IP 172.17.135.4.57628 > 172.17.131.32.6807: Flags [P.], seq > 1:201, ack 1, win 14600, options [nop,nop,TS[|tcp]> > 12:13:03.963547 IP 172.17.131.32.6807 > 172.17.135.4.57628: Flags [.], ack > 201, win 15544, options [nop,nop,TS[|tcp]> > 12:13:03.963700 IP 172.17.131.32.6807 > 172.17.135.4.57628: Flags [P.], seq > 1:10, ack 201, win 15544, options [nop,nop,TS[|tcp]> > 12:13:03.963794 IP 172.17.135.4.57628 > 172.17.131.32.6807: Flags [.], ack > 10, win 14600, options [nop,nop,TS[|tcp]> > 12:13:03.964024 IP 172.17.131.32.6807 > 172.17.135.4.57628: Flags [P.], seq > 10:282, ack 201, win 15544, options [nop,nop,TS[|tcp]> > 12:13:03.964091 IP 172.17.135.4.57628 > 172.17.131.32.6807: Flags [.], ack > 282, win 15544, options [nop,nop,TS[|tcp]> > 12:13:03.964438 IP 172.17.131.32.6807 > 172.17.135.4.57589: Flags [F.], seq > 1036, ack 18120026, win 5792, options [nop,nop,TS[|tcp]> > 12:13:03.964542 IP 172.17.135.4.57589 > 172.17.131.32.6807: Flags [R], seq > 2449506432, win 0, length 0 > > So if I'm reading this right, the client and server agree that > the server ACKed 18120026 twice. The client and server also > agree that the client retransmitted 18120026:18121474 nine times > from 11:57:36.213941 through 11:59:18.899063 (server clock). > > But the server never ACKed that packet. Too busy? > > I was collecting vmstat data during the run; here's the important bits: > > Fri Feb 10 11:56:51 MST 2012 > vmstat -w 8 16 > procs -------------------memory------------------ ---swap-- -----io---- > --system-- -----cpu------- > r b swpd free buff cache si so bi bo in > cs us sy id wa st > 13 10 0 250272 944 37859080 0 0 7 5346 1098 > 444 2 5 92 1 0 > 88 8 0 260472 944 36728776 0 0 0 1329838 > 257602 68861 19 73 5 4 0 > 100 10 0 241952 944 36066536 0 0 0 1635891 340724 > 85570 22 68 6 4 0 > 105 9 0 250288 944 34750820 0 0 0 1584816 433223 > 111462 21 73 4 3 0 > 126 3 0 259908 944 33841696 0 0 0 749648 > 225707 86716 9 83 4 3 0 > 157 2 0 245032 944 31572536 0 0 0 736841 252406 > 99083 9 81 5 5 0 > 45 17 0 246720 944 28877640 0 0 1 755085 > 282177 116551 8 77 9 5 0 Holy crap! That might explain why you aren't seeing anything. You are writing out over a 1.6 million blocks/sec. That too averaged over a 8 second interval. I bet the missed acks are when this is happening. What sort of I/O load is going through this system during those times? What sort of filesystem and Linux system are these OSDs on? Sridhar > 27 5 0 260556 944 27322948 0 0 0 553263 > 232682 132427 7 68 19 6 0 > 4 0 0 256552 944 26507508 0 0 0 271822 > 133540 113952 5 15 75 5 0 > 4 3 0 235236 944 26308308 0 0 0 181450 > 96027 101017 4 10 82 4 0 > 4 2 0 225372 944 26072048 0 0 0 200145 97401 > 100146 4 11 80 5 0 > 7 1 0 250940 944 25974752 0 0 0 92943 > 64015 78035 3 7 87 2 0 > 2 1 0 261712 944 25886872 0 0 0 152351 > 80963 99512 4 9 84 4 0 > 4 1 0 265056 944 25850216 0 0 0 92452 > 60790 75949 3 7 87 2 0 > 0 0 0 269164 944 25857592 0 0 0 87396 > 52994 67057 3 7 88 3 0 > 6 2 0 263672 944 25846192 0 0 0 110817 > 67707 75849 3 8 86 3 0 > Fri Feb 10 11:58:51 MST 2012 > vmstat -w 8 16 > procs -------------------memory------------------ ---swap-- -----io---- > --system-- -----cpu------- > r b swpd free buff cache si so bi bo in > cs us sy id wa st > 1 2 0 260620 944 25838996 0 0 6 7199 240 > 795 3 8 88 1 0 > 1 0 0 262124 944 25838936 0 0 0 108113 > 64640 75751 3 7 87 3 0 > 1 0 0 258700 944 25850148 0 0 0 94477 > 57952 68787 3 7 88 3 0 > 0 1 0 270144 944 25794068 0 0 0 92113 > 54901 73329 3 6 88 2 0 > 2 2 0 272036 944 25768044 0 0 0 57449 > 45552 61373 3 5 90 2 0 > 1 1 0 270024 944 25832600 0 0 0 47651 > 44594 60577 2 5 91 1 0 > 1 0 0 280648 944 25862304 0 0 1 54773 > 42668 58636 2 6 90 2 0 > 1 1 0 272132 944 25848136 0 0 0 41938 > 42310 57425 3 6 91 1 0 > 2 0 0 291272 944 25806644 0 0 1 41896 > 42259 58833 2 5 91 1 0 > 0 0 0 289392 944 25804128 0 0 0 32031 > 36699 51119 2 5 92 1 0 > 2 1 0 288420 944 25824956 0 0 0 42997 > 40542 55109 2 5 91 1 0 > 2 0 0 289076 944 25832792 0 0 0 31843 > 36438 49974 2 4 92 1 0 > 1 1 0 294600 944 25795512 0 0 0 35685 > 39307 56293 2 5 92 1 0 > 3 1 0 268708 944 25937656 0 0 0 148219 > 79498 87394 4 8 85 3 0 > 2 0 0 300100 944 25928888 0 0 0 87999 > 59708 73501 3 6 88 2 0 > 1 0 0 279988 944 25966636 0 0 0 71014 > 52225 69119 3 6 90 2 0 > > So the server might have been busy when 18120026:18121474 was first > received, but it was nearly idle for several of the retransmits. > > What am I missing? > > >>> >>> >>>> >>>> I will take a look at the additional output and see if anything pops >>>> out. I am assuming the below output was immediately after what you >>>> posted in your earlier email. >> >> >> i don't see anything out of the ordinary once things recover, the >> sender even starts to do TSO after a short while. > > > That's what I thought as well. > > Thanks -- Jim > > >> >> Sridhar >> >> >>> >>> >>> Yes. >>> >>> Thanks -- Jim >>> >>> >>>> >>>> >>>> Sridhar >>>> >>> >>> >>> -- >>> To unsubscribe from this list: send the line "unsubscribe ceph-devel" in >>> the body of a message to majordomo@...r.kernel.org >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >> >> >> > > > -- > To unsubscribe from this list: send the line "unsubscribe ceph-devel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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