[SERVER-82030] "Illegal instruction" on EL7 Ivy Bridge CPU Created: 10/Oct/23 Updated: 16/Oct/23 Resolved: 16/Oct/23 |
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| Status: | Closed |
| Project: | Core Server |
| Component/s: | None |
| Affects Version/s: | 5.0.21 |
| Fix Version/s: | None |
| Type: | Bug | Priority: | Major - P3 |
| Reporter: | Thomas Fromm | Assignee: | Noopur Gupta |
| Resolution: | Done | Votes: | 0 |
| Labels: | None | ||
| Remaining Estimate: | Not Specified | ||
| Time Spent: | Not Specified | ||
| Original Estimate: | Not Specified | ||
| Attachments: |
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| Operating System: | ALL | ||||||||
| Steps To Reproduce: | "Illegal instruction" happens, when executing mongod on CentOS 7 on a system with Ivy Bridge CPU. |
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| Description |
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The issue seems similar to: https://jira.mongodb.org/browse/MONGOSH-1604 Attached is cpuinfo and gdb output of: gdb -ex run -ex bt -ex 'disassemble $rip-100,$rip+100' --batch --args mongod Since we're running a lot of microservers with this generation of CPUs, the support of it is important to us.
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| Comments |
| Comment by Noopur Gupta [ 12/Oct/23 ] |
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AVX instructions(Single Instruction/Multiple dataset SIMD) are set of instructions added in the processors which contributes to improving performance. AVX (Advanced Vector Extension) requirement was added on MongoDB v5+ since it improves overall mongod performance capabilites.. Since most of the latest CPUs support AVX, MongoDB decided to provide one single support build type with AVX instructions. You can also find this helpful post on the Developer forum https://www.mongodb.com/community/forums/t/one-more-time-about-mongo-5-cpu-requirements/168858. Let us know if you have further questions on this. Thanks |
| Comment by Thomas Fromm [ 11/Oct/23 ] |
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I thought the lack of avx was only true for the previous microserver generation shipped with G5420, but the problem affects also the current series of HPE Microserve Gen10+ V2 shipped with Pentium G6405. So my questions at this point: Which benefits does mongod have from relying on avx that strong? |
| Comment by Thomas Fromm [ 10/Oct/23 ] |
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I noticed a bit late the requirement of AVX inside the documentation: https://www.mongodb.com/docs/v5.0/administration/production-notes/ |