RE: [Lsf] Preliminary Agenda and Activities for LSF

Shyam_Iyer
2011-03-29T18:11:15Z

> -----Original Message-----
> From: Vivek Goyal [mailto:vgoyal@redhat.com]
> Sent: Tuesday, March 29, 2011 1:34 PM
> To: Iyer, Shyam
> Cc: rwheeler@redhat.com; James.Bottomley@hansenpartnership.com;
> lsf@lists.linux-foundation.org; linux-fsdevel@vger.kernel.org; dm-
> devel@redhat.com; linux-scsi@vger.kernel.org
> Subject: Re: [Lsf] Preliminary Agenda and Activities for LSF
>
> On Tue, Mar 29, 2011 at 10:20:57AM -0700, Shyam_Iyer@dell.com wrote:
> >
> >
> > > -----Original Message-----
> > > From: linux-scsi-owner@vger.kernel.org [mailto:linux-scsi-
> > > owner@vger.kernel.org] On Behalf Of Ric Wheeler
> > > Sent: Tuesday, March 29, 2011 7:17 AM
> > > To: James Bottomley
> > > Cc: lsf@lists.linux-foundation.org; linux-fsdevel; linux-
> > > scsi@vger.kernel.org; device-mapper development
> > > Subject: Re: [Lsf] Preliminary Agenda and Activities for LSF
> > >
> > > On 03/29/2011 12:36 AM, James Bottomley wrote:
> > > > Hi All,
> > > >
> > > > Since LSF is less than a week away, the programme committee put
> > > together
> > > > a just in time preliminary agenda for LSF. As you can see there
> is
> > > > still plenty of empty space, which you can make suggestions (to
> this
> > > > list with appropriate general list cc's) for filling:
> > > >
> > > >
> > >
> https://spreadsheets.google.com/pub?hl=en&hl=en&key=0AiQMl7GcVa7OdFdNQz
> > > M5UDRXUnVEbHlYVmZUVHQ2amc&output=html
> > > >
> > > > If you don't make suggestions, the programme committee will feel
> > > > empowered to make arbitrary assignments based on your topic and
> > > attendee
> > > > email requests ...
> > > >
> > > > We're still not quite sure what rooms we will have at the Kabuki,
> but
> > > > we'll add them to the spreadsheet when we know (they should be
> close
> > > to
> > > > each other).
> > > >
> > > > The spreadsheet above also gives contact information for all the
> > > > attendees and the programme committee.
> > > >
> > > > Yours,
> > > >
> > > > James Bottomley
> > > > on behalf of LSF/MM Programme Committee
> > > >
> > >
> > > Here are a few topic ideas:
> > >
> > > (1) The first topic that might span IO & FS tracks (or just pull
> in
> > > device
> > > mapper people to an FS track) could be adding new commands that
> would
> > > allow
> > > users to grow/shrink/etc file systems in a generic way. The
> thought I
> > > had was
> > > that we have a reasonable model that we could reuse for these new
> > > commands like
> > > mount and mount.fs or fsck and fsck.fs. With btrfs coming down the
> > > road, it
> > > could be nice to identify exactly what common operations users want
> to
> > > do and
> > > agree on how to implement them. Alasdair pointed out in the
> upstream
> > > thread that
> > > we had a prototype here in fsadm.
> > >
> > > (2) Very high speed, low latency SSD devices and testing. Have we
> > > settled on the
> > > need for these devices to all have block level drivers? For S-ATA
> or
> > > SAS
> > > devices, are there known performance issues that require
> enhancements
> > > in
> > > somewhere in the stack?
> > >
> > > (3) The union mount versus overlayfs debate - pros and cons. What
> each
> > > do well,
> > > what needs doing. Do we want/need both upstream? (Maybe this can
> get 10
> > > minutes
> > > in Al's VFS session?)
> > >
> > > Thanks!
> > >
> > > Ric
> >
> > A few others that I think may span across I/O, Block fs..layers.
> >
> > 1) Dm-thinp target vs File system thin profile vs block map based
> thin/trim profile.
>
> > Facilitate I/O throttling for thin/trimmable storage. Online and
> Offline profil.
>
> Is above any different from block IO throttling we have got for block
> devices?
>
Yes.. so the throttling would be capacity based.. when the storage array wants us to throttle the I/O. Depending on the event we may keep getting space allocation write protect check conditions for writes until a user intervenes to stop I/O.

> > 2) Interfaces for SCSI, Ethernet/*transport configuration parameters
> floating around in sysfs, procfs. Architecting guidelines for accepting
> patches for hybrid devices.
> > 3) DM snapshot vs FS snapshots vs H/W snapshots. There is room for
> all and they have to help each other

For instance if you took a DM snapshot and the storage sent a check condition to the original dm device I am not sure if the DM snapshot would get one too..

If you had a scenario of taking H/W snapshot of an entire pool and decide to delete the individual DM snapshots the H/W snapshot would be inconsistent.

The blocks being managed by a DM-device would have moved (SCSI referrals). I believe Hannes is working on the referrals piece..

> > 4) B/W control - VM->DM->Block->Ethernet->Switch->Storage. Pick your
> subsystem and there are many non-cooperating B/W control constructs in
> each subsystem.
>
> Above is pretty generic. Do you have specific needs/ideas/concerns?
>
> Thanks
> Vivek
Yes.. if I limited by Ethernet b/w to 40% I don't need to limit I/O b/w via cgroups. Such bandwidth manipulations are network switch driven and cgroups never take care of these events from the Ethernet driver.

The TC classes route the network I/O to multiqueue groups and so theoretically you could have block queues 1:1 with the number of network multiqueues..

-Shyam