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a=z/mQ4Ysz8XfWz/Q5cLBRGdckG28=:19 a=lCpzRmAYbLLaTzLvsPZ7Mbvzbb8=:19 a=xqWC_Br6kY4A:10 a=IkcTkHD0fZMA:10 a=x6icFKpwvdMA:10 a=GoEa3M9JfhUA:10 a=VwQbUJbxAAAA:8 a=VabnemYjAAAA:8 a=tMj_ddulewJ9nrc7s50A:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=gKebqoRLp9LExxC7YDUY:22 X-Proofpoint-ORIG-GUID: OTpV40m4KLXCUNXAxjQiED84QW6N7k87 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMDA3MDE1NCBTYWx0ZWRfX999WtfIyML1Y IembpeHAaqY/Y9dfWsYgixCxzRu5GLyCi1JXvdEU0I2jTWhZwhbyCGEjBUDycNffbLetmc8Iwcw Drw2rtekw8Wb6xIWolUydI9ydUacxEpJJT7UQeTJ6PAMDrhz4QvBLeAh5N0AmB1MoEWZ9kbC5Am YRYehiXOeJgR4hi8KcWi43LN6BIknci1yQcR+5NPauYq8jkowJchzq1XrAJf3/j1fSfegEGJipX W3cOCoWbFNBrJEQvOzfpbizOk5ZyCJruIJdrj6wi29BhdnUBeJlMP6KJLB166ZfpjtdmErg0Xl9 Ui7NayGQjiYV2r+n9y4zNInGFiXLPqeYH6OeqtCMvp+zGV7OnRSeYI8fl/SwsXx6/+TV1gLpGAK XVrfJLATRLyZZ8kDh26rVUCRAGfgrQ== On 10/6/25 17:23, Chris Mason wrote: > On 10/6/25 4:23 PM, Joseph Salisbury wrote: >> Hi Chris, >> >> During testing, we are seeing a ~6% performance regression with the >> upstream stable v6.12.43 kernel (And Oracle UEK >> 6.12.0-104.43.4.el9uek.x86_64 kernel) when running the Phoronix >> pts/apache benchmark with 100 concurrent requests [0].  The regression >> is seen with the following hardware: >> >> PROCESSOR: Intel Xeon Platinum 8167M Core Count: 8 Thread Count: 16 >> Extensions: SSE 4.2 + AVX512CD + AVX2 + AVX + RDRAND + FSGSBASE Cache >> Size: 16 MB Microcode: 0x1 Core Family: Cascade Lake >> >> After performing a bisect, we found that the performance regression was >> introduced by the following commit: >> >> Stable v6.12.43: fc4289233e4b ("sched/fair: Bump sd->max_newidle_lb_cost >> when newidle balance fails") >> Mainline v6.17-rc1: 155213a2aed4 ("sched/fair: Bump >> sd->max_newidle_lb_cost when newidle balance fails") >> >> Reverting this commit causes the performance regression to not exist. >> >> I was hoping to get your feedback, since you are the patch author.  Do >> you think gathering any additional data will help diagnose this issue? > Hi everyone, > > Peter, we've had a collection of regression reports based on this > change, so it sounds like we need to make it less aggressive, or maybe > we need to make the degrading of the cost number more aggressive? > > Joe (and everyone else who has hit this), can I talk you into trying the > drgn from > https://urldefense.com/v3/__https://lore.kernel.org/lkml/2fbf24bc-e895-40de-9ff6-5c18b74b4300@meta.com/__;!!ACWV5N9M2RV99hQ!Pm-G5L97VLtQdDRHad16cdOnEwHxyKGHd8U1FSLtAY-oy2pNcbmCjTS1XRjq-ypIoQdJGkE_12KkAr0$ > > I'm curious if it degrades at all or just gets stuck up high. > > -chris Hi Chris, Thanks for the quick response! Yes, I will try out the drgn from the link you posted and provide feedback. Thanks, Joe