Thanks sage.
Retesting by using --test --weight ${rand} 0 , still in 40 OSDs, 10 per host
case:
New code average on 204.31 while old code average on 202.31
> -----Original Message-----
> From: Sage Weil [mailto:s...@newdream.net]
> Sent: Monday, October 19, 2015 10:18 AM
> To: Xusangdi
> Cc: Chen, Xiaoxi; ceph-devel@vger.kernel.org
> Subject: RE: chooseleaf may cause some unnecessary pg migrations
>
> On Mon, 19 Oct 2015, Xusangdi wrote:
> >
> > > -----Original Message-----
> > > From: ceph-devel-ow...@vger.kernel.org
> > > [mailto:ceph-devel-ow...@vger.kernel.org] On Behalf Of Chen, Xiaoxi
> > > Sent: Monday, October 19, 2015 9:11 AM
> > > To: xusangdi 11976 (RD)
> > > Cc: ceph-devel@vger.kernel.org
> > > Subject: RE: chooseleaf may cause some unnecessary pg migrations
> > >
> > > Sorry but not following...
> > >
> > > > then shut down one or more osds (please don't touch the crushmap,
> > > > just stop the osd service or kill
> > > its process).
> > >
> > > In this case, OSD is only down but not out, but will be marked out after
> 300s.
> > >
> > > So in what case your patch is helping?
> > >
> > > If you said your patch helps on "down and out" , then my
> > > experiment is exactly the case,
> > >
> >
> > I am afraid it is probably not. Could you tell me how did you simulate
> > the osd "down and out" situation using crushtool? If it was done by
> > arguments such as '--remove-item' or 'reweight-item', it modified the
> > crushmap and is not what I'm aiming for.
>
> There is a --weight argument (noted in usage near --test, which is the only
> piece that uses it). The crush map is not modified--only the weight vector
> that is passed in when a mapping is calculated (which is the equivalent of the
> in/out state in Ceph's OSDMap). This should let you simulate this case.
>
> When I'm debugging/understanding these issues I usually change the dprintk
> #define at the top of crush/mapper.c and use crushtool or osdmaptool to
> calculate a single mapping, comparing the log before and after a particular
> change.
>
> sage
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