* Increased Latencies when upgrading kernel version @ 2010-04-01 19:12 Taylor Lewick 2010-04-01 21:19 ` Eric Dumazet 0 siblings, 1 reply; 5+ messages in thread From: Taylor Lewick @ 2010-04-01 19:12 UTC (permalink / raw) To: netdev, linux-kernel For some time now we've been running an older kernel, 2.6.16.60. When we tried to upgrade, first going to 2.6.27.19 and then to 2.6.32.1 and 2.6.33.1 we noticed that latencies increased. At first we noticed it by doing network tests via udpping, netperf, etc. We made some tweaks, and were able to get network latency to within 1 to 2 microseconds of where we were previously on 2.6.16.60. Then we did some more testing, and noticed that system latency also seems higher. We've done our tests on identical hardware servers, same NICs, connected through same network gear. Basically, we've tried to keep everything identical except the kernel versions, and we are unable to achieve the same performance for system latency on the newer kernels, despite adjusting various kernel settings and recompiling. The latency differences are about 15 microseconds per transaction. At this point, I don't know what else to try. I haven't played around with the /proc/sys/kernel/sched_* paramaters under the newer kernels yet. Have tried changing pre-emption modes with little effect, in fact, voluntary preemption seems to be peforming the best for us. At this time the realtime patch isn't really an option for us to consider, at least not yet. Any suggestions? Is this a known issue when upgrading to more recent kernel versions? Thanks, Taylor ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Increased Latencies when upgrading kernel version 2010-04-01 19:12 Increased Latencies when upgrading kernel version Taylor Lewick @ 2010-04-01 21:19 ` Eric Dumazet 2010-04-02 1:53 ` Taylor Lewick 0 siblings, 1 reply; 5+ messages in thread From: Eric Dumazet @ 2010-04-01 21:19 UTC (permalink / raw) To: Taylor Lewick; +Cc: netdev, linux-kernel Le jeudi 01 avril 2010 à 14:12 -0500, Taylor Lewick a écrit : > For some time now we've been running an older kernel, 2.6.16.60. When > we tried to upgrade, first going to 2.6.27.19 and then to 2.6.32.1 and > 2.6.33.1 we noticed that latencies increased. At first we noticed it > by doing network tests via udpping, netperf, etc. We made some > tweaks, and were able to get network latency to within 1 to 2 > microseconds of where we were previously on 2.6.16.60. Then we did > some more testing, and noticed that system latency also seems higher. > > We've done our tests on identical hardware servers, same NICs, > connected through same network gear. Basically, we've tried to keep > everything identical except the kernel versions, and we are unable to > achieve the same performance for system latency on the newer kernels, > despite adjusting various kernel settings and recompiling. > > The latency differences are about 15 microseconds per transaction. > > At this point, I don't know what else to try. I haven't played around > with the /proc/sys/kernel/sched_* paramaters under the newer kernels > yet. Have tried changing pre-emption modes with little effect, in > fact, voluntary preemption seems to be peforming the best for us. > > At this time the realtime patch isn't really an option for us to > consider, at least not yet. > > Any suggestions? Is this a known issue when upgrading to more recent > kernel versions? > Hi Taylor Well, this is bit difficult to generically answer to your generic question. 15 us more latency per transaction seems pretty bad. Some inputs would be nice, describing your workload and software/hardware architecture. lspci cat /proc/cpuinfo cat /proc/interrupts dmesg ethtool -S eth0 ethtool -c eth0 ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Increased Latencies when upgrading kernel version 2010-04-01 21:19 ` Eric Dumazet @ 2010-04-02 1:53 ` Taylor Lewick 2010-04-05 17:34 ` Taylor Lewick 0 siblings, 1 reply; 5+ messages in thread From: Taylor Lewick @ 2010-04-02 1:53 UTC (permalink / raw) To: Eric Dumazet; +Cc: netdev, linux-kernel Okay. I will get this info out to the list Monday. Briefly, I'm using identical hardware (server), identical NICs, same drivers, connected to same switch, and using udpping, hackbench, and an internall written app to test latency. Without exception the evolution has looked like the following. 2.6.16.60 latencies for system and network are fast. Meaning hackbench and udpping win, and win by quite a bit. 2.6.27.19 was awful. 2.6.32.1 and 2.6.331. were better for networking (with some tweaks, i.e. disable netfilter, etc), and I was able to get networking latencies to within 1-3 microseconds of 2.6.16.60 latencies, but the hackbench results are still pretty bad. Again, I'll post numbers and more detailed hardware info on Monday when I'm back at office... On Thu, Apr 1, 2010 at 4:19 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote: > Le jeudi 01 avril 2010 à 14:12 -0500, Taylor Lewick a écrit : >> For some time now we've been running an older kernel, 2.6.16.60. When >> we tried to upgrade, first going to 2.6.27.19 and then to 2.6.32.1 and >> 2.6.33.1 we noticed that latencies increased. At first we noticed it >> by doing network tests via udpping, netperf, etc. We made some >> tweaks, and were able to get network latency to within 1 to 2 >> microseconds of where we were previously on 2.6.16.60. Then we did >> some more testing, and noticed that system latency also seems higher. >> >> We've done our tests on identical hardware servers, same NICs, >> connected through same network gear. Basically, we've tried to keep >> everything identical except the kernel versions, and we are unable to >> achieve the same performance for system latency on the newer kernels, >> despite adjusting various kernel settings and recompiling. >> >> The latency differences are about 15 microseconds per transaction. >> >> At this point, I don't know what else to try. I haven't played around >> with the /proc/sys/kernel/sched_* paramaters under the newer kernels >> yet. Have tried changing pre-emption modes with little effect, in >> fact, voluntary preemption seems to be peforming the best for us. >> >> At this time the realtime patch isn't really an option for us to >> consider, at least not yet. >> >> Any suggestions? Is this a known issue when upgrading to more recent >> kernel versions? >> > > Hi Taylor > > Well, this is bit difficult to generically answer to your generic > question. 15 us more latency per transaction seems pretty bad. > > Some inputs would be nice, describing your workload and > software/hardware architecture. > > lspci > cat /proc/cpuinfo > cat /proc/interrupts > dmesg > ethtool -S eth0 > ethtool -c eth0 > > > > ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Increased Latencies when upgrading kernel version 2010-04-02 1:53 ` Taylor Lewick @ 2010-04-05 17:34 ` Taylor Lewick 2010-04-06 14:10 ` Xianghua Xiao 0 siblings, 1 reply; 5+ messages in thread From: Taylor Lewick @ 2010-04-05 17:34 UTC (permalink / raw) To: Eric Dumazet; +Cc: netdev, linux-kernel Okay, don't know what to officially file this under, as a regression with regards to performance or what, but here is the data. Again, I've noticed system and network latency appear to have worsened with later kernel versions. I was turned onto this problem via the following links: http://www.kernel.org/pub/linux/kernel/people/christoph/ols2009/ols-2009-paper.pdf and http://kerneltrap.org/mailarchive/linux-netdev/2009/4/16/5491284 So I set up a test on two servers with Identical hardware, servers, nics, etc, and used hackbench, udpping, and an internally written app to compare latency. Here are just the hackbench results with just the averages across a 5 runs for two different hackbench tests. The 2.6.16 and 2.6.27 kernels as set up were configured with voluntary preemption, and 250 HZ, so I just repeated that initially for 2.6.33.1 test. I also tested no preemption at same HZ setting of 250. I ran 2.6.16.60 on one server, and the other kernel versions on another server. These tests are repeatable across different servers, as in I verified I don't have a bad server. Kernel Version HB1 (25 process 300) HB2 (100 process 300) 2.6.16.60 .5402 1.8946 2.6.27.19 .619 2.6268 2.6.32.3-voluntary .5636 2.3484 2.6.33.1-voluntary .5404 2.2872 2.6.33.1-nopreempt .5606 2.3466 So 2.6.16.60 is fast, 2.6.27.19 is slow, and 2.6.33.1 with voluntary preemption is the next best, but results didn't hold up well as Hackbench tests used larger numbers of groups., for example, 2.6.16.60 and 2.6.33.1-voluntary were basically the same for HB1, but that didn't hold when hackebnch tests used more groups. At this point, I'm looking for ideas in kernel build to tweak, but I'm not a developer. So SLAB vs SLUB, sparse vs dense IRQ numbering, etc. Running a -rt kernel isn't an option at this time. I did test that as well, and latencies were quite a bit worse, but I wasn't adjusting code to take advantage of a real time OS. I can make some changes or repeat tests. Below is some hardware comparisons betweent the two machines. Differences I noticed was more interrupts and CPU flags on later kernel version. HostA 2.6.16.60 cat /proc/interrupts CPU0 CPU1 CPU2 CPU3 CPU4 CPU5 CPU6 CPU7 0: 108509762 0 0 0 0 0 0 0 IO-APIC-edge timer 8: 1 0 0 0 0 0 0 0 IO-APIC-edge rtc 9: 0 0 0 0 0 0 0 0 IO-APIC-level acpi 58: 305 0 5157735 220 2980100 5927 1187 0 IO-APIC-level libata 162: 0 0 0 0 0 0 0 0 IO-APIC-level uhci_hcd:usb1 170: 0 0 0 0 0 0 0 0 IO-APIC-level uhci_hcd:usb2 177: 6326 0 229018 0 283720 35597 367 0 IO-APIC-level megasas 178: 122 0 1784 1103 3531 20 1457 0 IO-APIC-level uhci_hcd:usb3, ehci_hcd:usb6 186: 0 0 0 0 0 0 0 0 IO-APIC-level uhci_hcd:usb4 194: 22 0 0 0 0 0 0 0 IO-APIC-level ehci_hcd:usb5 210: 1790109 577 0 0 0 0 0 0 PCI-MSI-X eth4-0 218: 233811 93 0 0 0 0 0 0 PCI-MSI-X eth4-1 NMI: 0 0 0 0 0 0 0 0 LOC: 108509683 108509662 108509637 108509614 108509588 108509566 108509541 108509516 ERR: 7 MIS: 0 lspci 00:00.0 Host bridge: Intel Corporation QuickPath Architecture I/O Hub to ESI Port (rev 13) 00:01.0 PCI bridge: Intel Corporation QuickPath Architecture I/O Hub PCI Express Root Port 1 (rev 13) 00:03.0 PCI bridge: Intel Corporation QuickPath Architecture I/O Hub PCI Express Root Port 3 (rev 13) 00:07.0 PCI bridge: Intel Corporation QuickPath Architecture I/O Hub PCI Express Root Port 7 (rev 13) 00:09.0 PCI bridge: Intel Corporation QuickPath Architecture I/O Hub PCI Express Root Port 9 (rev 13) 00:14.0 PIC: Intel Corporation QuickPath Architecture I/O Hub System Management Registers (rev 13) 00:14.1 PIC: Intel Corporation QuickPath Architecture I/O Hub GPIO and Scratch Pad Registers (rev 13) 00:14.2 PIC: Intel Corporation QuickPath Architecture I/O Hub Control Status and RAS Registers (rev 13) 00:16.0 System peripheral: Intel Corporation DMA Engine (rev 13) 00:16.1 System peripheral: Intel Corporation DMA Engine (rev 13) 00:16.2 System peripheral: Intel Corporation DMA Engine (rev 13) 00:16.3 System peripheral: Intel Corporation DMA Engine (rev 13) 00:16.4 System peripheral: Intel Corporation DMA Engine (rev 13) 00:16.5 System peripheral: Intel Corporation DMA Engine (rev 13) 00:16.6 System peripheral: Intel Corporation DMA Engine (rev 13) 00:16.7 System peripheral: Intel Corporation DMA Engine (rev 13) 00:1a.0 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #4 (rev 02) 00:1a.1 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #5 (rev 02) 00:1a.7 USB Controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #2 (rev 02) 00:1c.0 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 1 (rev 02) 00:1d.0 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #1 (rev 02) 00:1d.1 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #2 (rev 02) 00:1d.7 USB Controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #1 (rev 02) 00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev 92) 00:1f.0 ISA bridge: Intel Corporation 82801IB (ICH9) LPC Interface Controller (rev 02) 00:1f.2 IDE interface: Intel Corporation 82801IB (ICH9) 2 port SATA IDE Controller (rev 02) 03:00.0 RAID bus controller: LSI Logic / Symbios Logic MegaRAID SAS 1078 (rev 04) 04:00.0 PCI bridge: Integrated Device Technology, Inc. Unknown device 8018 (rev 0e) 05:02.0 PCI bridge: Integrated Device Technology, Inc. Unknown device 8018 (rev 0e) 05:04.0 PCI bridge: Integrated Device Technology, Inc. Unknown device 8018 (rev 0e) 06:00.0 Ethernet controller: Intel Corporation 82575GB Gigabit Network Connection (rev 02) 06:00.1 Ethernet controller: Intel Corporation 82575GB Gigabit Network Connection (rev 02) 07:00.0 Ethernet controller: Intel Corporation 82575GB Gigabit Network Connection (rev 02) 07:00.1 Ethernet controller: Intel Corporation 82575GB Gigabit Network Connection (rev 02) 08:00.0 Ethernet controller: Solarflare Communications Unknown device 0710 (rev 02) 09:03.0 VGA compatible controller: Matrox Graphics, Inc. Unknown device 0532 (rev 0a) cat /proc/cpuinfo (just showing first CPU for brevity) processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 26 model name : Intel(R) Xeon(R) CPU X5570 @ 2.93GHz stepping : 5 cpu MHz : 2926.090 cache size : 8192 KB physical id : 1 siblings : 4 core id : 0 cpu cores : 4 fpu : yes fpu_exception : yes cpuid level : 11 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx rdtscp lm constant_tsc pni monitor d s_cpl vmx est tm2 cx16 xtpr dca popcnt lahf_lm bogomips : 5857.34 clflush size : 64 cache_alignment : 64 address sizes : 40 bits physical, 48 bits virtual power management: ethtool -c eth4 Coalesce parameters for eth4: Adaptive RX: on TX: off stats-block-usecs: 0 sample-interval: 0 pkt-rate-low: 0 pkt-rate-high: 0 rx-usecs: 0 rx-frames: 0 rx-usecs-irq: 60 rx-frames-irq: 0 tx-usecs: 0 tx-frames: 0 tx-usecs-irq: 0 tx-frames-irq: 0 rx-usecs-low: 0 rx-frame-low: 0 tx-usecs-low: 0 tx-frame-low: 0 rx-usecs-high: 0 rx-frame-high: 0 tx-usecs-high: 0 tx-frame-high: 0 HostB 2.6.33.1 CPU0 CPU1 CPU2 CPU3 CPU4 CPU5 CPU6 CPU7 0: 8637 0 0 0 0 0 0 0 IO-APIC-edge timer 1: 2 0 0 0 0 0 0 0 IO-APIC-edge i8042 3: 2 0 0 0 0 0 0 0 IO-APIC-edge 4: 2 0 0 0 0 0 0 0 IO-APIC-edge 8: 1 0 0 0 0 0 0 0 IO-APIC-edge rtc0 9: 0 0 0 0 0 0 0 0 IO-APIC-fasteoi acpi 12: 4 0 0 0 0 0 0 0 IO-APIC-edge i8042 16: 7434 683 0 0 0 0 0 0 IO-APIC-fasteoi megasas 17: 0 0 0 0 0 0 0 0 IO-APIC-fasteoi uhci_hcd:usb3 18: 0 0 0 0 0 0 0 0 IO-APIC-fasteoi uhci_hcd:usb4 19: 23 0 0 0 0 0 0 0 IO-APIC-fasteoi ehci_hcd:usb1 20: 0 0 0 0 0 0 0 0 IO-APIC-fasteoi uhci_hcd:usb6 21: 129 0 15 0 0 0 0 0 IO-APIC-fasteoi ehci_hcd:usb2, uhci_hcd:usb5 23: 369 0 0 0 0 0 0 0 IO-APIC-fasteoi ata_piix 67: 2346 731 0 0 0 0 0 0 PCI-MSI-edge eth4-0 68: 1809 404 0 0 0 0 0 0 PCI-MSI-edge eth4-1 NMI: 0 0 0 0 0 0 0 0 Non-maskable interrupts LOC: 33071 38348 47397 23246 15715 11065 9004 10391 Local timer interrupts SPU: 0 0 0 0 0 0 0 0 Spurious interrupts PMI: 0 0 0 0 0 0 0 0 Performance monitoring interrupts PND: 0 0 0 0 0 0 0 0 Performance pending work RES: 2490 2124 4187 4974 1724 5548 1892 2871 Rescheduling interrupts CAL: 497 2166 141 115 133 144 140 144 Function call interrupts TLB: 243 244 928 945 289 187 134 93 TLB shootdowns TRM: 0 0 0 0 0 0 0 0 Thermal event interrupts THR: 0 0 0 0 0 0 0 0 Threshold APIC interrupts MCE: 0 0 0 0 0 0 0 0 Machine check exceptions MCP: 2 2 2 2 2 2 2 2 Machine check polls ERR: 7 MIS: 0 lspci 00:00.0 Host bridge: Intel Corporation X58 I/O Hub to ESI Port (rev 13) 00:01.0 PCI bridge: Intel Corporation X58 I/O Hub PCI Express Root Port 1 (rev 13) 00:03.0 PCI bridge: Intel Corporation X58 I/O Hub PCI Express Root Port 3 (rev 13) 00:07.0 PCI bridge: Intel Corporation X58 I/O Hub PCI Express Root Port 7 (rev 13) 00:09.0 PCI bridge: Intel Corporation X58 I/O Hub PCI Express Root Port 9 (rev 13) 00:14.0 PIC: Intel Corporation X58 I/O Hub System Management Registers (rev 13) 00:14.1 PIC: Intel Corporation X58 I/O Hub GPIO and Scratch Pad Registers (rev 13) 00:14.2 PIC: Intel Corporation X58 I/O Hub Control Status and RAS Registers (rev 13) 00:1a.0 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #4 (rev 02) 00:1a.1 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #5 (rev 02) 00:1a.7 USB Controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #2 (rev 02) 00:1c.0 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 1 (rev 02) 00:1d.0 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #1 (rev 02) 00:1d.1 USB Controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #2 (rev 02) 00:1d.7 USB Controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #1 (rev 02) 00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev 92) 00:1f.0 ISA bridge: Intel Corporation 82801IB (ICH9) LPC Interface Controller (rev 02) 00:1f.2 IDE interface: Intel Corporation 82801IB (ICH9) 2 port SATA IDE Controller (rev 02) 03:00.0 RAID bus controller: LSI Logic / Symbios Logic MegaRAID SAS 1078 (rev 04) 04:00.0 PCI bridge: Integrated Device Technology, Inc. PES12N3A PCI Express Switch (rev 0e) 05:02.0 PCI bridge: Integrated Device Technology, Inc. PES12N3A PCI Express Switch (rev 0e) 05:04.0 PCI bridge: Integrated Device Technology, Inc. PES12N3A PCI Express Switch (rev 0e) 06:00.0 Ethernet controller: Intel Corporation 82575GB Gigabit Network Connection (rev 02) 06:00.1 Ethernet controller: Intel Corporation 82575GB Gigabit Network Connection (rev 02) 07:00.0 Ethernet controller: Intel Corporation 82575GB Gigabit Network Connection (rev 02) 07:00.1 Ethernet controller: Intel Corporation 82575GB Gigabit Network Connection (rev 02) 08:00.0 Ethernet controller: Solarflare Communications SFC4000 rev B [Solarstorm] (rev 02) 09:03.0 VGA compatible controller: Matrox Graphics, Inc. MGA G200eW WPCM450 (rev 0a) cat /proc/cpuinfo (just showing first CPU for brevity) processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 26 model name : Intel(R) Xeon(R) CPU X5570 @ 2.93GHz stepping : 5 cpu MHz : 2925.888 cache size : 8192 KB physical id : 1 siblings : 4 core id : 0 cpu cores : 4 apicid : 16 initial apicid : 16 fpu : yes fpu_exception : yes cpuid level : 11 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm constant_tsc arch_perfmon pebs bt s rep_good xtopology nonstop_tsc aperfmperf pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm dca sse4_1 sse4_2 popcnt lahf_lm ida tpr_shadow vnmi flexpriority ept vpid bogomips : 5851.77 clflush size : 64 cache_alignment : 64 address sizes : 40 bits physical, 48 bits virtual power management: ethtool -c eth4 Coalesce parameters for eth4: Adaptive RX: on TX: off stats-block-usecs: 0 sample-interval: 0 pkt-rate-low: 0 pkt-rate-high: 0 rx-usecs: 0 rx-frames: 0 rx-usecs-irq: 60 rx-frames-irq: 0 tx-usecs: 0 tx-frames: 0 tx-usecs-irq: 0 tx-frames-irq: 0 rx-usecs-low: 0 rx-frame-low: 0 tx-usecs-low: 0 tx-frame-low: 0 rx-usecs-high: 0 rx-frame-high: 0 tx-usecs-high: 0 tx-frame-high: 0 On Thu, Apr 1, 2010 at 8:53 PM, Taylor Lewick <taylor.lewick@gmail.com> wrote: > Okay. I will get this info out to the list Monday. Briefly, I'm > using identical hardware (server), identical NICs, same drivers, > connected to same switch, and using udpping, hackbench, and an > internall written app to test latency. Without exception the > evolution has looked like the following. > > 2.6.16.60 latencies for system and network are fast. Meaning > hackbench and udpping win, and win by quite a bit. > > 2.6.27.19 was awful. 2.6.32.1 and 2.6.331. were better for networking > (with some tweaks, i.e. disable netfilter, etc), and I was able to get > networking latencies to within 1-3 microseconds of 2.6.16.60 > latencies, but the hackbench results are still pretty bad. > > Again, I'll post numbers and more detailed hardware info on Monday > when I'm back at office... > > On Thu, Apr 1, 2010 at 4:19 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote: >> Le jeudi 01 avril 2010 à 14:12 -0500, Taylor Lewick a écrit : >>> For some time now we've been running an older kernel, 2.6.16.60. When >>> we tried to upgrade, first going to 2.6.27.19 and then to 2.6.32.1 and >>> 2.6.33.1 we noticed that latencies increased. At first we noticed it >>> by doing network tests via udpping, netperf, etc. We made some >>> tweaks, and were able to get network latency to within 1 to 2 >>> microseconds of where we were previously on 2.6.16.60. Then we did >>> some more testing, and noticed that system latency also seems higher. >>> >>> We've done our tests on identical hardware servers, same NICs, >>> connected through same network gear. Basically, we've tried to keep >>> everything identical except the kernel versions, and we are unable to >>> achieve the same performance for system latency on the newer kernels, >>> despite adjusting various kernel settings and recompiling. >>> >>> The latency differences are about 15 microseconds per transaction. >>> >>> At this point, I don't know what else to try. I haven't played around >>> with the /proc/sys/kernel/sched_* paramaters under the newer kernels >>> yet. Have tried changing pre-emption modes with little effect, in >>> fact, voluntary preemption seems to be peforming the best for us. >>> >>> At this time the realtime patch isn't really an option for us to >>> consider, at least not yet. >>> >>> Any suggestions? Is this a known issue when upgrading to more recent >>> kernel versions? >>> >> >> Hi Taylor >> >> Well, this is bit difficult to generically answer to your generic >> question. 15 us more latency per transaction seems pretty bad. >> >> Some inputs would be nice, describing your workload and >> software/hardware architecture. >> >> lspci >> cat /proc/cpuinfo >> cat /proc/interrupts >> dmesg >> ethtool -S eth0 >> ethtool -c eth0 >> >> >> >> > ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: Increased Latencies when upgrading kernel version 2010-04-05 17:34 ` Taylor Lewick @ 2010-04-06 14:10 ` Xianghua Xiao 0 siblings, 0 replies; 5+ messages in thread From: Xianghua Xiao @ 2010-04-06 14:10 UTC (permalink / raw) To: Taylor Lewick; +Cc: Eric Dumazet, netdev, linux-kernel On Mon, Apr 5, 2010 at 12:34 PM, Taylor Lewick <taylor.lewick@gmail.com> wrote: > Okay, don't know what to officially file this under, as a regression > with regards to performance or what, but here is the data. Again, > I've noticed system and network latency appear to have worsened with > later kernel versions. > > I was turned onto this problem via the following links: > http://www.kernel.org/pub/linux/kernel/people/christoph/ols2009/ols-2009-paper.pdf > and http://kerneltrap.org/mailarchive/linux-netdev/2009/4/16/5491284 > > So I set up a test on two servers with Identical hardware, servers, > nics, etc, and used hackbench, udpping, and an internally written app > to compare latency. > > Here are just the hackbench results with just the averages across a 5 > runs for two different hackbench tests. The 2.6.16 and 2.6.27 kernels > as set up were configured with voluntary preemption, and 250 HZ, so I > just repeated that initially for 2.6.33.1 test. I also tested no > preemption at same HZ setting of 250. > > I ran 2.6.16.60 on one server, and the other kernel versions on > another server. These tests are repeatable across different servers, > as in I verified I > don't have a bad server. > > Kernel Version HB1 (25 process 300) HB2 (100 process 300) > 2.6.16.60 .5402 1.8946 > 2.6.27.19 .619 2.6268 > 2.6.32.3-voluntary .5636 2.3484 > 2.6.33.1-voluntary .5404 2.2872 > 2.6.33.1-nopreempt .5606 2.3466 > > So 2.6.16.60 is fast, 2.6.27.19 is slow, and 2.6.33.1 with voluntary > preemption is the next best, but results didn't hold up well as > Hackbench tests used larger numbers of groups., for example, 2.6.16.60 > and 2.6.33.1-voluntary were basically the same for HB1, but that > didn't hold when hackebnch tests used more groups. > > At this point, I'm looking for ideas in kernel build to tweak, but I'm > not a developer. So SLAB vs SLUB, sparse vs dense IRQ numbering, etc. > Running a -rt kernel isn't an option at this time. I did test that as > well, and latencies were quite a bit worse, but I wasn't adjusting > code to take advantage of a real time OS. > > I can make some changes or repeat tests. > > Below is some hardware comparisons betweent the two machines. > Differences I noticed was more interrupts and CPU flags on later > kernel version. > > HostA 2.6.16.60 > cat /proc/interrupts > CPU0 CPU1 CPU2 CPU3 CPU4 CPU5 > CPU6 CPU7 > 0: 108509762 0 0 0 0 0 > 0 0 IO-APIC-edge timer > 8: 1 0 0 0 0 0 > 0 0 IO-APIC-edge rtc > 9: 0 0 0 0 0 0 > 0 0 IO-APIC-level acpi > 58: 305 0 5157735 220 2980100 5927 > 1187 0 IO-APIC-level libata > 162: 0 0 0 0 0 0 > 0 0 IO-APIC-level uhci_hcd:usb1 > 170: 0 0 0 0 0 0 > 0 0 IO-APIC-level uhci_hcd:usb2 > 177: 6326 0 229018 0 283720 35597 > 367 0 IO-APIC-level megasas > 178: 122 0 1784 1103 3531 20 > 1457 0 IO-APIC-level uhci_hcd:usb3, ehci_hcd:usb6 > 186: 0 0 0 0 0 0 > 0 0 IO-APIC-level uhci_hcd:usb4 > 194: 22 0 0 0 0 0 > 0 0 IO-APIC-level ehci_hcd:usb5 > 210: 1790109 577 0 0 0 0 > 0 0 PCI-MSI-X eth4-0 > 218: 233811 93 0 0 0 0 > 0 0 PCI-MSI-X eth4-1 > NMI: 0 0 0 0 0 0 > 0 0 > LOC: 108509683 108509662 108509637 108509614 108509588 108509566 > 108509541 108509516 > ERR: 7 > MIS: 0 > > lspci > 00:00.0 Host bridge: Intel Corporation QuickPath Architecture I/O Hub > to ESI Port (rev 13) > 00:01.0 PCI bridge: Intel Corporation QuickPath Architecture I/O Hub > PCI Express Root Port 1 (rev 13) > 00:03.0 PCI bridge: Intel Corporation QuickPath Architecture I/O Hub > PCI Express Root Port 3 (rev 13) > 00:07.0 PCI bridge: Intel Corporation QuickPath Architecture I/O Hub > PCI Express Root Port 7 (rev 13) > 00:09.0 PCI bridge: Intel Corporation QuickPath Architecture I/O Hub > PCI Express Root Port 9 (rev 13) > 00:14.0 PIC: Intel Corporation QuickPath Architecture I/O Hub System > Management Registers (rev 13) > 00:14.1 PIC: Intel Corporation QuickPath Architecture I/O Hub GPIO and > Scratch Pad Registers (rev 13) > 00:14.2 PIC: Intel Corporation QuickPath Architecture I/O Hub Control > Status and RAS Registers (rev 13) > 00:16.0 System peripheral: Intel Corporation DMA Engine (rev 13) > 00:16.1 System peripheral: Intel Corporation DMA Engine (rev 13) > 00:16.2 System peripheral: Intel Corporation DMA Engine (rev 13) > 00:16.3 System peripheral: Intel Corporation DMA Engine (rev 13) > 00:16.4 System peripheral: Intel Corporation DMA Engine (rev 13) > 00:16.5 System peripheral: Intel Corporation DMA Engine (rev 13) > 00:16.6 System peripheral: Intel Corporation DMA Engine (rev 13) > 00:16.7 System peripheral: Intel Corporation DMA Engine (rev 13) > 00:1a.0 USB Controller: Intel Corporation 82801I (ICH9 Family) USB > UHCI Controller #4 (rev 02) > 00:1a.1 USB Controller: Intel Corporation 82801I (ICH9 Family) USB > UHCI Controller #5 (rev 02) > 00:1a.7 USB Controller: Intel Corporation 82801I (ICH9 Family) USB2 > EHCI Controller #2 (rev 02) > 00:1c.0 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express > Port 1 (rev 02) > 00:1d.0 USB Controller: Intel Corporation 82801I (ICH9 Family) USB > UHCI Controller #1 (rev 02) > 00:1d.1 USB Controller: Intel Corporation 82801I (ICH9 Family) USB > UHCI Controller #2 (rev 02) > 00:1d.7 USB Controller: Intel Corporation 82801I (ICH9 Family) USB2 > EHCI Controller #1 (rev 02) > 00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev 92) > 00:1f.0 ISA bridge: Intel Corporation 82801IB (ICH9) LPC Interface > Controller (rev 02) > 00:1f.2 IDE interface: Intel Corporation 82801IB (ICH9) 2 port SATA > IDE Controller (rev 02) > 03:00.0 RAID bus controller: LSI Logic / Symbios Logic MegaRAID SAS > 1078 (rev 04) > 04:00.0 PCI bridge: Integrated Device Technology, Inc. Unknown device > 8018 (rev 0e) > 05:02.0 PCI bridge: Integrated Device Technology, Inc. Unknown device > 8018 (rev 0e) > 05:04.0 PCI bridge: Integrated Device Technology, Inc. Unknown device > 8018 (rev 0e) > 06:00.0 Ethernet controller: Intel Corporation 82575GB Gigabit Network > Connection (rev 02) > 06:00.1 Ethernet controller: Intel Corporation 82575GB Gigabit Network > Connection (rev 02) > 07:00.0 Ethernet controller: Intel Corporation 82575GB Gigabit Network > Connection (rev 02) > 07:00.1 Ethernet controller: Intel Corporation 82575GB Gigabit Network > Connection (rev 02) > 08:00.0 Ethernet controller: Solarflare Communications Unknown device > 0710 (rev 02) > 09:03.0 VGA compatible controller: Matrox Graphics, Inc. Unknown > device 0532 (rev 0a) > > cat /proc/cpuinfo (just showing first CPU for brevity) > processor : 0 > vendor_id : GenuineIntel > cpu family : 6 > model : 26 > model name : Intel(R) Xeon(R) CPU X5570 @ 2.93GHz > stepping : 5 > cpu MHz : 2926.090 > cache size : 8192 KB > physical id : 1 > siblings : 4 > core id : 0 > cpu cores : 4 > fpu : yes > fpu_exception : yes > cpuid level : 11 > wp : yes > flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge > mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall > nx rdtscp lm constant_tsc pni monitor d > s_cpl vmx est tm2 cx16 xtpr dca popcnt lahf_lm > bogomips : 5857.34 > clflush size : 64 > cache_alignment : 64 > address sizes : 40 bits physical, 48 bits virtual > power management: > > ethtool -c eth4 > Coalesce parameters for eth4: > Adaptive RX: on TX: off > stats-block-usecs: 0 > sample-interval: 0 > pkt-rate-low: 0 > pkt-rate-high: 0 > > rx-usecs: 0 > rx-frames: 0 > rx-usecs-irq: 60 > rx-frames-irq: 0 > > tx-usecs: 0 > tx-frames: 0 > tx-usecs-irq: 0 > tx-frames-irq: 0 > > rx-usecs-low: 0 > rx-frame-low: 0 > tx-usecs-low: 0 > tx-frame-low: 0 > > rx-usecs-high: 0 > rx-frame-high: 0 > tx-usecs-high: 0 > tx-frame-high: 0 > > > HostB 2.6.33.1 > CPU0 CPU1 CPU2 CPU3 CPU4 CPU5 > CPU6 CPU7 > 0: 8637 0 0 0 0 > 0 0 0 IO-APIC-edge timer > 1: 2 0 0 0 0 > 0 0 0 IO-APIC-edge i8042 > 3: 2 0 0 0 0 > 0 0 0 IO-APIC-edge > 4: 2 0 0 0 0 > 0 0 0 IO-APIC-edge > 8: 1 0 0 0 0 > 0 0 0 IO-APIC-edge rtc0 > 9: 0 0 0 0 0 > 0 0 0 IO-APIC-fasteoi acpi > 12: 4 0 0 0 0 > 0 0 0 IO-APIC-edge i8042 > 16: 7434 683 0 0 0 > 0 0 0 IO-APIC-fasteoi megasas > 17: 0 0 0 0 0 > 0 0 0 IO-APIC-fasteoi uhci_hcd:usb3 > 18: 0 0 0 0 0 > 0 0 0 IO-APIC-fasteoi uhci_hcd:usb4 > 19: 23 0 0 0 0 > 0 0 0 IO-APIC-fasteoi ehci_hcd:usb1 > 20: 0 0 0 0 0 > 0 0 0 IO-APIC-fasteoi uhci_hcd:usb6 > 21: 129 0 15 0 0 > 0 0 0 IO-APIC-fasteoi ehci_hcd:usb2, > uhci_hcd:usb5 > 23: 369 0 0 0 0 > 0 0 0 IO-APIC-fasteoi ata_piix > 67: 2346 731 0 0 0 > 0 0 0 PCI-MSI-edge eth4-0 > 68: 1809 404 0 0 0 > 0 0 0 PCI-MSI-edge eth4-1 > NMI: 0 0 0 0 0 > 0 0 0 Non-maskable interrupts > LOC: 33071 38348 47397 23246 15715 > 11065 9004 10391 Local timer interrupts > SPU: 0 0 0 0 0 > 0 0 0 Spurious interrupts > PMI: 0 0 0 0 0 > 0 0 0 Performance monitoring interrupts > PND: 0 0 0 0 0 > 0 0 0 Performance pending work > RES: 2490 2124 4187 4974 1724 > 5548 1892 2871 Rescheduling interrupts > CAL: 497 2166 141 115 133 > 144 140 144 Function call interrupts > TLB: 243 244 928 945 289 > 187 134 93 TLB shootdowns > TRM: 0 0 0 0 0 > 0 0 0 Thermal event interrupts > THR: 0 0 0 0 0 > 0 0 0 Threshold APIC interrupts > MCE: 0 0 0 0 0 > 0 0 0 Machine check exceptions > MCP: 2 2 2 2 2 > 2 2 2 Machine check polls > ERR: 7 > MIS: 0 > > lspci > 00:00.0 Host bridge: Intel Corporation X58 I/O Hub to ESI Port (rev 13) > 00:01.0 PCI bridge: Intel Corporation X58 I/O Hub PCI Express Root > Port 1 (rev 13) > 00:03.0 PCI bridge: Intel Corporation X58 I/O Hub PCI Express Root > Port 3 (rev 13) > 00:07.0 PCI bridge: Intel Corporation X58 I/O Hub PCI Express Root > Port 7 (rev 13) > 00:09.0 PCI bridge: Intel Corporation X58 I/O Hub PCI Express Root > Port 9 (rev 13) > 00:14.0 PIC: Intel Corporation X58 I/O Hub System Management Registers (rev 13) > 00:14.1 PIC: Intel Corporation X58 I/O Hub GPIO and Scratch Pad > Registers (rev 13) > 00:14.2 PIC: Intel Corporation X58 I/O Hub Control Status and RAS > Registers (rev 13) > 00:1a.0 USB Controller: Intel Corporation 82801I (ICH9 Family) USB > UHCI Controller #4 (rev 02) > 00:1a.1 USB Controller: Intel Corporation 82801I (ICH9 Family) USB > UHCI Controller #5 (rev 02) > 00:1a.7 USB Controller: Intel Corporation 82801I (ICH9 Family) USB2 > EHCI Controller #2 (rev 02) > 00:1c.0 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express > Port 1 (rev 02) > 00:1d.0 USB Controller: Intel Corporation 82801I (ICH9 Family) USB > UHCI Controller #1 (rev 02) > 00:1d.1 USB Controller: Intel Corporation 82801I (ICH9 Family) USB > UHCI Controller #2 (rev 02) > 00:1d.7 USB Controller: Intel Corporation 82801I (ICH9 Family) USB2 > EHCI Controller #1 (rev 02) > 00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev 92) > 00:1f.0 ISA bridge: Intel Corporation 82801IB (ICH9) LPC Interface > Controller (rev 02) > 00:1f.2 IDE interface: Intel Corporation 82801IB (ICH9) 2 port SATA > IDE Controller (rev 02) > 03:00.0 RAID bus controller: LSI Logic / Symbios Logic MegaRAID SAS > 1078 (rev 04) > 04:00.0 PCI bridge: Integrated Device Technology, Inc. PES12N3A PCI > Express Switch (rev 0e) > 05:02.0 PCI bridge: Integrated Device Technology, Inc. PES12N3A PCI > Express Switch (rev 0e) > 05:04.0 PCI bridge: Integrated Device Technology, Inc. PES12N3A PCI > Express Switch (rev 0e) > 06:00.0 Ethernet controller: Intel Corporation 82575GB Gigabit Network > Connection (rev 02) > 06:00.1 Ethernet controller: Intel Corporation 82575GB Gigabit Network > Connection (rev 02) > 07:00.0 Ethernet controller: Intel Corporation 82575GB Gigabit Network > Connection (rev 02) > 07:00.1 Ethernet controller: Intel Corporation 82575GB Gigabit Network > Connection (rev 02) > 08:00.0 Ethernet controller: Solarflare Communications SFC4000 rev B > [Solarstorm] (rev 02) > 09:03.0 VGA compatible controller: Matrox Graphics, Inc. MGA G200eW > WPCM450 (rev 0a) > > cat /proc/cpuinfo (just showing first CPU for brevity) > processor : 0 > vendor_id : GenuineIntel > cpu family : 6 > model : 26 > model name : Intel(R) Xeon(R) CPU X5570 @ 2.93GHz > stepping : 5 > cpu MHz : 2925.888 > cache size : 8192 KB > physical id : 1 > siblings : 4 > core id : 0 > cpu cores : 4 > apicid : 16 > initial apicid : 16 > fpu : yes > fpu_exception : yes > cpuid level : 11 > wp : yes > flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge > mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe > syscall nx rdtscp lm constant_tsc arch_perfmon pebs bt > s rep_good xtopology nonstop_tsc aperfmperf pni dtes64 monitor ds_cpl > vmx est tm2 ssse3 cx16 xtpr pdcm dca sse4_1 sse4_2 popcnt lahf_lm ida > tpr_shadow vnmi flexpriority ept vpid > bogomips : 5851.77 > clflush size : 64 > cache_alignment : 64 > address sizes : 40 bits physical, 48 bits virtual > power management: > > ethtool -c eth4 > Coalesce parameters for eth4: > Adaptive RX: on TX: off > stats-block-usecs: 0 > sample-interval: 0 > pkt-rate-low: 0 > pkt-rate-high: 0 > > rx-usecs: 0 > rx-frames: 0 > rx-usecs-irq: 60 > rx-frames-irq: 0 > > tx-usecs: 0 > tx-frames: 0 > tx-usecs-irq: 0 > tx-frames-irq: 0 > > rx-usecs-low: 0 > rx-frame-low: 0 > tx-usecs-low: 0 > tx-frame-low: 0 > > rx-usecs-high: 0 > rx-frame-high: 0 > tx-usecs-high: 0 > tx-frame-high: 0 > > > > On Thu, Apr 1, 2010 at 8:53 PM, Taylor Lewick <taylor.lewick@gmail.com> wrote: >> Okay. I will get this info out to the list Monday. Briefly, I'm >> using identical hardware (server), identical NICs, same drivers, >> connected to same switch, and using udpping, hackbench, and an >> internall written app to test latency. Without exception the >> evolution has looked like the following. >> >> 2.6.16.60 latencies for system and network are fast. Meaning >> hackbench and udpping win, and win by quite a bit. >> >> 2.6.27.19 was awful. 2.6.32.1 and 2.6.331. were better for networking >> (with some tweaks, i.e. disable netfilter, etc), and I was able to get >> networking latencies to within 1-3 microseconds of 2.6.16.60 >> latencies, but the hackbench results are still pretty bad. >> >> Again, I'll post numbers and more detailed hardware info on Monday >> when I'm back at office... >> >> On Thu, Apr 1, 2010 at 4:19 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote: >>> Le jeudi 01 avril 2010 à 14:12 -0500, Taylor Lewick a écrit : >>>> For some time now we've been running an older kernel, 2.6.16.60. When >>>> we tried to upgrade, first going to 2.6.27.19 and then to 2.6.32.1 and >>>> 2.6.33.1 we noticed that latencies increased. At first we noticed it >>>> by doing network tests via udpping, netperf, etc. We made some >>>> tweaks, and were able to get network latency to within 1 to 2 >>>> microseconds of where we were previously on 2.6.16.60. Then we did >>>> some more testing, and noticed that system latency also seems higher. >>>> >>>> We've done our tests on identical hardware servers, same NICs, >>>> connected through same network gear. Basically, we've tried to keep >>>> everything identical except the kernel versions, and we are unable to >>>> achieve the same performance for system latency on the newer kernels, >>>> despite adjusting various kernel settings and recompiling. >>>> >>>> The latency differences are about 15 microseconds per transaction. >>>> >>>> At this point, I don't know what else to try. I haven't played around >>>> with the /proc/sys/kernel/sched_* paramaters under the newer kernels >>>> yet. Have tried changing pre-emption modes with little effect, in >>>> fact, voluntary preemption seems to be peforming the best for us. >>>> >>>> At this time the realtime patch isn't really an option for us to >>>> consider, at least not yet. >>>> >>>> Any suggestions? Is this a known issue when upgrading to more recent >>>> kernel versions? >>>> >>> >>> Hi Taylor >>> >>> Well, this is bit difficult to generically answer to your generic >>> question. 15 us more latency per transaction seems pretty bad. >>> >>> Some inputs would be nice, describing your workload and >>> software/hardware architecture. >>> >>> lspci >>> cat /proc/cpuinfo >>> cat /proc/interrupts >>> dmesg >>> ethtool -S eth0 >>> ethtool -c eth0 >>> >>> >>> >>> >> > Just want to ack you here, I upgraded a 2.6.18 kernel to 2.6.33.1 on a shipping product and the performance(hackbench, latency, cpu usage,etc) is a lot worse on the same hardware platform. We tried 2.6.27 before and it's also bad. I'm tring various CONFIG options and so far nothing really helped. I'm using the RT patch. Xianghua ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2010-04-06 14:10 UTC | newest] Thread overview: 5+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2010-04-01 19:12 Increased Latencies when upgrading kernel version Taylor Lewick 2010-04-01 21:19 ` Eric Dumazet 2010-04-02 1:53 ` Taylor Lewick 2010-04-05 17:34 ` Taylor Lewick 2010-04-06 14:10 ` Xianghua Xiao
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s).