Re: O->A loan

[jaimef%mauthesis.com@localhost]

Hello Yamamoto-san

I have run dbench on ufs/wapbl with diagnostics disabled.
http://linbsd.org/yamt3.png


On Thu, 12 Jan 2012, YAMAMOTO Takashi wrote:

> Date: Thu, 12 Jan 2012 03:31:59 +0000 (UTC)
> From: YAMAMOTO Takashi <yamt%mwd.biglobe.ne.jp@localhost>
> To: jaimef%mauthesis.com@localhost
> Cc: chuq%chuq.com@localhost, tech-kern%netbsd.org@localhost
> Subject: Re: O->A loan
>
> hi,
>
> > I did not remove DIAGNOSTIC.
> > Would you like me to rerun without DIAGNOSTIC?
>
> yes, please.
>
> YAMAMOTO Takashi
>
> > On Thu, 12 Jan 2012, YAMAMOTO Takashi wrote:
> >
> > > Date: Thu, 12 Jan 2012 03:14:33 +0000 (UTC)
> > > From: YAMAMOTO Takashi <yamt%mwd.biglobe.ne.jp@localhost>
> > > To: jaimef%mauthesis.com@localhost
> > > Cc: chuq%chuq.com@localhost, tech-kern%netbsd.org@localhost
> > > Subject: Re: O->A loan
> > >
> > > hi,
> > >
> > > thanks for benchmark!
> > >
> > > was it without DIAGNOSTIC?
> > >
> > > YAMAMOTO Takashi
> > >
> > > > Hello Yamamoto-san,
> > > >
> > > > I ran dbench on the same system with yamt-pagecache, yamt-pagecache
> > > > without a-o loan, and yamt-pagecache-base3.
> > > > http://linbsd.org/yamt.png
> > > > The tests were run three times on each kernel and the results were
> > > > consistent between reboots/runs.
> > > >
> > > > Thanks.
> > > >
> > > > On Tue, 27 Dec 2011, YAMAMOTO Takashi wrote:
> > > >
> > > > > Date: Tue, 27 Dec 2011 02:53:29 +0000 (UTC)
> > > > > From: YAMAMOTO Takashi <yamt%mwd.biglobe.ne.jp@localhost>
> > > > > To: chuq%chuq.com@localhost
> > > > > Cc: tech-kern%netbsd.org@localhost
> > > > > Subject: Re: O->A loan
> > > > >
> > > > > hi,
> > > > >
> > > > > i made read with O->A loaning work for easy cases (ie. no locking difficulty)
> > > > > on yamt-pagecache branch so that someone interested can benchmark.
> > > > >
> > > > > YAMAMOTO Takashi
> > > > >
> > > > > > hi,
> > > > > >
> > > > > > > On Tue, Nov 29, 2011 at 06:38:27AM +0000, YAMAMOTO Takashi wrote:
> > > > > > > > O->A loaned pages installed on the user address space would have a different
> > > > > > > > owner than the usual map->entry.uvm_obj.
> > > > > > > > although it was not a problem when you wrote this patch, at least some
> > > > > > > > non-mechanical changes would be required after the recent locking
> > > > > > > > changes in this area.  namely, uvm_map_lock_entry etc now assumes that
> > > > > > > > any pages mapped in a map entry belong to either the entry's amap or
> > > > > > > > underlying object.
> > > > > > >
> > > > > > > ok, I didn't think it would be entirely mechanical.  :-)
> > > > > > >
> > > > > > > what if the O->A loan code also changed the entry's uvm_obj to be the vnode
> > > > > > > that the pages really belong to?  if the loan range in the amap is fully
> > > > > > > populated (which it is in this context) then that shouldn't affect the
> > > > > > > logical contents of the entry, it would just cause anyone locking the entry
> > > > > > > to also lock the vnode.  if the range of the loan is smaller than the
> > > > > > > range of the entry, we could split the entry.  do you think that would work?
> > > > > >
> > > > > > it might work, but i have some concerns:
> > > > > > - entry fragmentation
> > > > > > - the extra uobj reference keeps the file even after unlink
> > > > > >
> > > > > > YAMAMOTO Takashi
> > > > > >
> > > > > > > -Chuck