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Re: [dm-devel] [PATCH] EnhanceIO ssd caching software



Hi Darrick, 

> -----Original Message-----
> From: Darrick J. Wong [mailto:darrick wong oracle com]
> Sent: Wednesday, February 27, 2013 3:15 AM
> To: Sanoj Unnikrishnan
> Cc: OS Engineering; Greg Kroah-Hartman; LKML; Jens Axboe; 王金浦; Amit
> Kale; dm-devel redhat com; koverstreet google com; thornber redhat com
> Subject: Re: [PATCH] EnhanceIO ssd caching software
> 
> On Mon, Feb 18, 2013 at 05:42:38PM +0800, Sanoj Unnikrishnan wrote:
> > > -----Original Message-----
> > > From: Darrick J. Wong [mailto:darrick wong oracle com]
> > > Sent: Saturday, February 16, 2013 2:02 AM
> > > To: OS Engineering
> > > Cc: Greg Kroah-Hartman; LKML; Jens Axboe; Sanoj Unnikrishnan;
> 王金浦;
> > > Amit Kale; dm-devel redhat com; koverstreet google com;
> > > thornber redhat com
> > > Subject: Re: [PATCH] EnhanceIO ssd caching software
> > >
> > > [Resending with dm-devel, Kent, and Joe on cc.  Sorry for the
> > > noise.]
> > >
> > > On Fri, Feb 15, 2013 at 02:02:38PM +0800, OS Engineering wrote:
> > > > Hi Greg, Jens,
> > > >
> > > > We are submitting EnhanceIO(TM) software driver for an inclusion
> > > > in
> > > linux
> > > > staging tree. Present state of this driver is beta. We have been
> > > posting it
> > > > for a few weeks, while it was maintained at github. It is still
> > > > being cleaned-up and is being tested by LKML members. Inclusion
> in
> > > > linux
> > > staging
> > > > tree will make testing and reviewing easier and help a future
> > > integration in
> > > > Linux kernel.
> > > >
> > > > Could you please include it?
> >
> > > >
> > > > Signed-off-by:
> > > > Amit Kale <akale stec-inc com>
> > > > Sanoj Unnikrishnan <sunnikrishnan stec-inc com> Darrick J. Wong
> > > > <darrick wong oracle com> Jinpu Wang <jinpuwang gmail com>
> > >
> > > Each of these email addresses needs to have the "S-o-b:" prefix
> >
> > > Also, you ought to run this patch through scripts/checkpatch.pl, as
> > > there are quite a lot of style errors.
> >
> > we will fix these in the next patch.
> >
> >
> > > > +       Write-back improves write latency by writing application
> > > requested data
> > > > +       only to SSD. This data, referred to as dirty data, is
> > > > + copied
> > > later to
> > >
> > > How much later?
> > >
> >
> > This is triggered by a set of thresholds.
> > per cache dirty high and low watermark.
> > per cache set dirty high and low watermark.
> > and a time based threshold.
> > If any of the high watermarks or time based interval is triggered
> clean is initiated.
> >
> > These thresholds are all configurable through sysctl.
> 
> Is there a way for a user application to force a cache flush?  It looks
> as though a REQ_FLUSH will cause both SSD and HDD to flush their write
> caches, but I couldn't find anything that would suggest writing all the
> dirty blocks in the cache out to the HDD.


There is a clean command in eio_cli which flushes all the dirty data on user input.
 
Thanks and regards,
Sanoj


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