----- Original Message ---- > From: Chuck Lever <chucklever@xxxxxxxxx> > To: Martin Knoblauch <knobi@xxxxxxxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>; Greg Banks <gnb@xxxxxxxxxxxxxxxxx>; linux-nfs list <linux-nfs@xxxxxxxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; Peter zijlstra <a.p.zijlstra@xxxxxxxxx> > Sent: Thursday, September 18, 2008 8:24:42 PM > Subject: Re: [RFC][Resend] Make NFS-Client readahead tunable > > On Thu, Sep 18, 2008 at 6:53 AM, Martin Knoblauch wrote: > > ----- Original Message ---- > > > >> From: Andrew Morton > >> To: Martin Knoblauch > >> Cc: Greg Banks ; linux-nfs list > ; linux-kernel@xxxxxxxxxxxxxxx; Peter zijlstra > > >> Sent: Thursday, September 18, 2008 10:47:33 AM > >> Subject: Re: [RFC][Resend] Make NFS-Client readahead tunable > >> > >> On Thu, 18 Sep 2008 01:38:57 -0700 (PDT) Martin Knoblauch > >> wrote: > >> > >> > > No. mount(8) will pass unrecognised options straight down into the > >> > > filesystem driver. > >> > > > >> > > >> > Has that always been the case, or is it a recent change? I have to support > >> RHEL4 userland, which is not really new. > >> > >> It's been that way for ever and ever. It's how all these guys: > >> > >> y:/usr/src/25> grep Opt_ fs/*/super.c|wc > >> 781 2626 33703 > >> > >> get handled. > > > > while that seems to be not to complicated, I seem to have a problem passing > the mount options to the kernel. They come down as mount data version "6". > Apparently mount(8) or mount.nfs(8) are doing the parsing and send down the > legacy data block. So, what is the minimum version of mount or mount.nfs that > pass the options down unaltered? > > The mount command has passed a string of options to the kernel for > particular file systems for a while, but the facility for the NFS > client to parse a string of mount options in the kernel was added only > recently -- at least 2.6.23 or 2.6.24 is required to support this. > Before this, the mount command parsed these options. > I understand that. Question remains, which version of the mount(8) or nfs.mount(8) command do I need to pass the options to the kernel. > For RHEL 4, based on 2.6.9, you are stuck. It uses a binary structure > whose fields must match between the kernel and user space. For RH > enterprise kernels, the ABI cannot change in a given release, so RH > wouldn't take a patch to change the data structure that mount uses. > You would have to maintain such a change yourself, and build your own > kernels and mount command after each RHEL 4 update is released. > For implementation/testing purposes I have some freedom in what userland I run. My systems are mainly RHEL4, but I have long junked the 2.6.9 based kernels. > I agree that a mount option would allow more fine-grained control over > readahead. A system wide parameter controlling readahead has always > been a weakness. Readahead, as implemented in the VFS, has a > *per-file descriptor* context, however, which operates automatically > (and can be tuned at run-time by an application with [mf]advise(2). > The per-file descriptor stuff is not applicable in my case, as I do not have controll over programms acessing the files. > As a future feature, this might work in better combination with the > per-mount bdi changes proposed by Peter to provide maximal flexibility > without exposing yet another confusing knob that could help some > workloads but hurt others. > Thats why I am open to experiment, but need to know which userland tools support the direct passing of mount options to the NFS client. Cheers Martin -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
