Date: Thu, 28 Jan 2021 05:02:42 +0900 (JST) From: Yasuhiro Kimura <yasu@utahime.org> To: freebsd-current@freebsd.org Subject: Re: Waiting for bufdaemon Message-ID: <20210128.050242.1986722766748729591.yasu@utahime.org> In-Reply-To: <20210116.040323.136067379540977557.yasu@utahime.org> References: <7c4da243-52ff-c5ee-3d56-1ae651286e0e@alvermark.net> <20210115.201030.1395690536446474720.yasu@utahime.org> <20210116.040323.136067379540977557.yasu@utahime.org>
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From: Yasuhiro Kimura <yasu@utahime.org>
Subject: Re: Waiting for bufdaemon
Date: Sat, 16 Jan 2021 04:03:23 +0900 (JST)
> From: Yasuhiro Kimura <yasu@utahime.org>
> Subject: Re: Waiting for bufdaemon
> Date: Fri, 15 Jan 2021 20:10:30 +0900 (JST)
>
>> I have been experiencing same problem with my 13-CURRENT amd64
>> VirtualBox VM for about a month. The conditions that the problem
>> happens are unclear and all what I can say is
>>
>> * It happens only after I login in the VM and do something for a
>> while. If I boot the VM and shut it down immediately, it never
>> happens.
>> * When the problem happens, one or more unkillable processes seem to
>> be left.
>
> CPU of my host is not AMD but Intel. According to the
> /var/run/dmesg.boot of VM, information of CPU is as following.
>
> CPU: Intel(R) Core(TM) i7-9700 CPU @ 3.00GHz (3000.09-MHz K8-class CPU)
> Origin="GenuineIntel" Id=0x906ed Family=0x6 Model=0x9e Stepping=13
> Features=0x1783fbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,MMX,FXSR,SSE,SSE2,HTT>
> Features2=0x5eda2203<SSE3,PCLMULQDQ,SSSE3,CX16,PCID,SSE4.1,SSE4.2,MOVBE,POPCNT,AESNI,XSAVE,OSXSAVE,AVX,RDRAND>
> AMD Features=0x28100800<SYSCALL,NX,RDTSCP,LM>
> AMD Features2=0x121<LAHF,ABM,Prefetch>
> Structured Extended Features=0x842421<FSGSBASE,AVX2,INVPCID,NFPUSG,RDSEED,CLFLUSHOPT>
> Structured Extended Features3=0x30000400<MD_CLEAR,L1DFL,ARCH_CAP>
> IA32_ARCH_CAPS=0x29<RDCL_NO,SKIP_L1DFL_VME,MDS_NO>
> TSC: P-state invariant
>
> Just FYI.
It took for a while to investigate, but according to the result of
bisect following commit is the source of problem in my case.
----------------------------------------------------------------------
commit 84eaf2ccc6a
Author: Konstantin Belousov <kib@FreeBSD.org>
Date: Mon Dec 21 19:02:31 2020 +0200
x86: stop punishing VMs with low priority for TSC timecounter
I suspect that virtualization techniques improved from the time when we
have to effectively disable TSC use in VM. For instance, it was reported
(complained) in https://github.com/JuliaLang/julia/issues/38877 that
FreeBSD is groundlessly slow on AWS with some loads.
Remove the check and start watching for complaints.
Reviewed by: emaste, grehan
Discussed with: cperciva
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D27629
----------------------------------------------------------------------
I confirmed the problem still happens with 5c325977b11 but reverting
above commit fixes it.
---
Yasuhiro Kimura
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