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1c942771-8bcc-4773-3c76-08dc90092d5a X-MS-Exchange-CrossTenant-AuthSource: CO6PR10MB5409.namprd10.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 19 Jun 2024 02:40:27.3390 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: nK61pD0acLa2IHs7BHMZC0hi42MCArJlBb8plkc8PYdvhb6RuFB/iASB9KveB54v44ifWzEM0sg8kKX1JiYf59ebK4jdpDbrnwcnHi0PO0I= X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR10MB6075 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.680,FMLib:17.12.28.16 definitions=2024-06-18_08,2024-06-17_01,2024-05-17_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=999 suspectscore=0 malwarescore=0 phishscore=0 spamscore=0 mlxscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2405010000 definitions=main-2406190019 X-Proofpoint-GUID: t66UigU2qFoJnU7PWv730HKuoXrTCQae X-Proofpoint-ORIG-GUID: t66UigU2qFoJnU7PWv730HKuoXrTCQae Shrikanth Hegde writes: > On 6/15/24 8:34 PM, Shrikanth Hegde wrote: >> >> >> On 6/10/24 12:53 PM, Ankur Arora wrote: >>> >> _auto. >>>> >>>> 6.10-rc1: >>>> ========= >>>> 10:09:50 AM CPU %usr %nice %sys %iowait %irq %soft %steal %guest %gnice %idle >>>> 09:45:23 AM all 4.14 0.00 77.57 0.00 16.92 0.00 0.00 0.00 0.00 1.37 >>>> 09:45:24 AM all 4.42 0.00 77.62 0.00 16.76 0.00 0.00 0.00 0.00 1.20 >>>> 09:45:25 AM all 4.43 0.00 77.45 0.00 16.94 0.00 0.00 0.00 0.00 1.18 >>>> 09:45:26 AM all 4.45 0.00 77.87 0.00 16.68 0.00 0.00 0.00 0.00 0.99 >>>> >>>> PREEMPT_AUTO: >>>> =========== >>>> 10:09:50 AM CPU %usr %nice %sys %iowait %irq %soft %steal %guest %gnice %idle >>>> 10:09:56 AM all 3.11 0.00 72.59 0.00 21.34 0.00 0.00 0.00 0.00 2.96 >>>> 10:09:57 AM all 3.31 0.00 73.10 0.00 20.99 0.00 0.00 0.00 0.00 2.60 >>>> 10:09:58 AM all 3.40 0.00 72.83 0.00 20.85 0.00 0.00 0.00 0.00 2.92 >>>> 10:10:00 AM all 3.21 0.00 72.87 0.00 21.19 0.00 0.00 0.00 0.00 2.73 >>>> 10:10:01 AM all 3.02 0.00 72.18 0.00 21.08 0.00 0.00 0.00 0.00 3.71 >>>> >>>> Used bcc tools hardirq and softirq to see if irq are increasing. softirq implied there are more >>>> timer,sched softirq. Numbers vary between different samples, but trend seems to be similar. >>> >>> Yeah, the %sys is lower and %irq, higher. Can you also see where the >>> increased %irq is? For instance are the resched IPIs numbers greater? >> >> Hi Ankur, >> >> >> Used mpstat -I ALL to capture this info for 20 seconds. >> >> HARDIRQ per second: >> =================== >> 6.10: >> =================== >> 18 19 22 23 48 49 50 51 LOC BCT LOC2 SPU PMI MCE NMI WDG DBL >> --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- >> 417956.86 1114642.30 1712683.65 2058664.99 0.00 0.00 18.30 0.39 31978.37 0.00 0.35 351.98 0.00 0.00 0.00 6405.54 329189.45 >> >> Preempt_auto: >> =================== >> 18 19 22 23 48 49 50 51 LOC BCT LOC2 SPU PMI MCE NMI WDG DBL >> --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- >> 609509.69 1910413.99 1923503.52 2061876.33 0.00 0.00 19.14 0.30 31916.59 0.00 0.45 497.88 0.00 0.00 0.00 6825.49 88247.85 >> >> 18,19,22,23 are called XIVE interrupts. These are IPI interrupts. I am not sure which type of IPI are these. will have to see why its increasing. >> >> >> SOFTIRQ per second: >> =================== >> 6.10: >> =================== >> HI TIMER NET_TX NET_RX BLOCK IRQ_POLL TASKLET SCHED HRTIMER RCU >> 0.00 3966.47 0.00 18.25 0.59 0.00 0.34 12811.00 0.00 9693.95 >> >> Preempt_auto: >> =================== >> HI TIMER NET_TX NET_RX BLOCK IRQ_POLL TASKLET SCHED HRTIMER RCU >> 0.00 4871.67 0.00 18.94 0.40 0.00 0.25 13518.66 0.00 15732.77 >> >> Note: RCU softirq seems to increase significantly. Not sure which one triggers. still trying to figure out why. >> It maybe irq triggering to softirq or softirq causing more IPI. >> >> >> >> Also, Noticed a below config difference which gets removed in preempt auto. This happens because PREEMPTION make them as N. Made the changes in kernel/Kconfig.locks to get them >> enabled. I still see the same regression in hackbench. These configs still may need attention? >> >> 6.10 | preempt auto >> CONFIG_INLINE_SPIN_UNLOCK_IRQ=y | CONFIG_UNINLINE_SPIN_UNLOCK=y >> CONFIG_INLINE_READ_UNLOCK=y | ---------------------------------------------------------------------------- >> CONFIG_INLINE_READ_UNLOCK_IRQ=y | ---------------------------------------------------------------------------- >> CONFIG_INLINE_WRITE_UNLOCK=y | ---------------------------------------------------------------------------- >> CONFIG_INLINE_WRITE_UNLOCK_IRQ=y | ---------------------------------------------------------------------------- >> >> > > Did an experiment keeping the number of CPU constant, while changing the number of sockets they span across. > When all CPU belong to same socket, there is no regression w.r.t to PREEMPT_AUTO. Regression starts when the CPUs start > spanning across sockets. Ah. That's really interesting. So, upto 160 CPUs was okay? > Since Preempt auto by default enables preempt count, I think that may cause the regression. I see Powerpc uses generic implementation > which may not scale well. Yeah this would explain why I don't see similar behaviour on a 384 CPU x86 box. Also, IIRC the powerpc numbers on preempt=full were significantly worse than preempt=none. That test might also be worth doing once you have the percpu based method working. > Will try to shift to percpu based method and see. will get back if I can get that done successfully. Sounds good to me. Thanks Ankur