Date: Tue, 10 Jun 2014 11:04:26 -0700 From: Peter Grehan <grehan@freebsd.org> To: Willem Jan Withagen <wjw@digiware.nl> Cc: FreeBSD virtualization <freebsd-virtualization@freebsd.org> Subject: Re: Bheve: Slow linux syscalls on AMD Message-ID: <539748AA.5060005@freebsd.org> In-Reply-To: <53971C3A.30406@digiware.nl> References: <5388B56D.1000501@digiware.nl> <20140530212900.6B74B6BF@hub.freebsd.org> <53891BC1.9050701@digiware.nl> <53891EAA.8040105@freebsd.org> <538927FC.3000903@digiware.nl> <53939AE2.80804@freebsd.org> <539434B6.6020804@digiware.nl> <CALnRwMQFmQRxg0jWi5tqXFXARsj-sD5F3wAAXdTvNf7%2BVPoezw@mail.gmail.com> <5394817F.4030203@digiware.nl> <53948DA5.4040000@digiware.nl> <53962141.8070702@freebsd.org> <5396D18C.8000401@digiware.nl> <53970F5A.8060900@freebsd.org> <53971C3A.30406@digiware.nl>
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Hi Willem, > I've got KTR compiled in, but last time I switched it on. > I got swamped in traffic, and I sort of got locked out of the server... :( > Could also be because I was writing it to a file as well. > > So you'll have to help/tell me what to do. For looking at this, I'd use one single-vCPU guest to avoid KTR noise from other vCPU/guests. The problem shows up with this so no issue there. First, boot the VM and get it sitting at a shell prompt idling. On the host, first see that there are enough entries in the KTR buffer # sysctl debug.ktr.entries <32/64K is a good number> If it's too small, it can be bumped up # sysctl debug.ktr.entries=65536 debug.ktr.entries: 8192 -> 65536 The bhyve kernel module uses the ktr mask value 0x01. This should be turned off by default: # sysctl debug.ktr.mask debug.ktr.mask: 0 To get some traces, turn this on for a few seconds # sysctl debug.ktr.mask=1 ; sleep 3 ; sysctl debug.ktr.mask=0 The ktr trace buffer can now be examined: # ktrdump -ct To repeat/rerun the process, make sure the ktr buffer is cleared with # sysctl debug.ktr.clear=1 debug.ktr.clear: 0 -> 0 later, Peter.
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