Re: [RFC] extending splice for copy offloading

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Wed, Sep 25, 2013 at 03:02:29PM -0400, Anna Schumaker wrote:
> On Wed, Sep 25, 2013 at 2:38 PM, Zach Brown <zab@xxxxxxxxxx> wrote:
> >
> > Hrmph.  I had composed a reply to you during Plumbers but.. something
> > happened to it :).  Here's another try now that I'm back.
> >
> >> > Some things to talk about:
> >> > - I really don't care about the naming here.  If you do, holler.
> >> > - We might want different flags for file-to-file splicing and acceleration
> >>
> >> Yes, I think "copy" and "reflink" needs to be differentiated.
> >
> > I initially agreed but I'm not so sure now.  The problem is that we
> > can't know whether the acceleration is copying or not.  XCOPY on some
> > array may well do some shared referencing tricks.  The nfs COPY op can
> > have a server use btrfs reflink, or ext* and XCOPY, or .. who knows.  At
> > some point we have to admit that we have no way to determine the
> > relative durability of writes.  Storage can do a lot to make writes more
> > or less fragile that we have no visibility of.  SSD FTLs can log a bunch
> > of unrelated sectors on to one flash failure domain.
> >
> > And if such a flag couldn't *actually* guarantee anything for a bunch of
> > storage topologies, well, let's not bother with it.
> >
> > The only flag I'm in favour of now is one that has splice return rather
> > than falling back to manual page cache reads and writes.  It's more like
> > O_NONBLOCK than any kind of data durability hint.
> 
> For reference, I'm planning to have the NFS server do the fallback
> when it copies since any local copy will be faster than a read and
> write over the network.

Agreed, this is definitely the reasonable thing to do.

- z
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html




[Index of Archives]     [Linux Ext4 Filesystem]     [Union Filesystem]     [Filesystem Testing]     [Ceph Users]     [Ecryptfs]     [AutoFS]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux Cachefs]     [Reiser Filesystem]     [Linux RAID]     [Samba]     [Device Mapper]     [CEPH Development]
  Powered by Linux