* Eric W. Biederman <ebiederm at xmission.com> wrote: > Cliff Wickman <cpw at sgi.com> writes: > > > From: Cliff Wickman <cpw at sgi.com> > > > > The copy of /proc/vmcore to a user buffer proceeds much faster > > if the kernel addresses memory as cached. > > > > With this patch we have seen an increase in transfer rate from less than > > 15MB/s to 80-460MB/s, depending on size of the transfer. This makes > > a big difference in time needed to save a system dump. > > > > (Does anyone know of a reason why copy_oldmem_page() would need > > to use uncached addresses?) > > > > Diffed against 2.6.36-rc3 > > I believe this code simply predates being able to specify the > caching attributes at ioremap time. Being cached in this case > actually looks more correct, as that is the default for RAM > and we are talking about RAM. > > Ultimately either there is another cpu running wild with these pages > mapped with some random set of attributes, and we cannot get the > permissions right or we have captured all of the cpus and this is the > only mapping so it doesn't matter. > > Acked-by: "Eric W. Biederman" <ebiederm at xmission.com> Applied, thanks guys. Note, i also added a -stable tag, as kdump is typically used with enterprise setups and we want this (low-risk, high-impact) improvement to be propagated far back the -stable series. Thanks, Ingo
