On Sat, Nov 20, 2010 at 02:16:12AM +0000, Ben Hutchings wrote: > On Fri, 2010-11-19 at 13:42 -0800, Greg KH wrote: > > 2.6.32-stable review patch. If anyone has any objections, please let us know. > > > > ------------------ > > > > From: Cliff Wickman <cpw at sgi.com> > > > > commit 3ee48b6af49cf534ca2f481ecc484b156a41451d upstream. > > > > During the reading of /proc/vmcore the kernel is doing > > ioremap()/iounmap() repeatedly. And the buildup of un-flushed > > vm_area_struct's is causing a great deal of overhead. (rb_next() > > is chewing up most of that time). > > > > This solution is to provide function set_iounmap_nonlazy(). It > > causes a subsequent call to iounmap() to immediately purge the > > vma area (with try_purge_vmap_area_lazy()). > > > > With this patch we have seen the time for writing a 250MB > > compressed dump drop from 71 seconds to 44 seconds. > [...] > > Useful, but it doesn't seem to meet the criteria for stable updates. I disagree, it's a major speedup, and an obvious bugfix for the problem. thanks, greg k-h
