On Thu, May 17, 2018 at 12:32:07PM -0700, Dan Williams wrote: > On Thu, May 17, 2018 at 11:37 AM, Matthew Wilcox <[email protected]> wrote: > > > > I plucked this patch from my XArray work. It seems self-contained enough > > that it could go into the DAX tree for merging this cycle. > > > > From 8cb56f4ba36af38814ca7b8ba030a66384e59a21 Mon Sep 17 00:00:00 2001 > > From: Matthew Wilcox <[email protected]> > > Date: Thu, 29 Mar 2018 22:41:18 -0400 > > Subject: [PATCH] dax: Fix use of zero page > > > > Use my_zero_pfn instead of ZERO_PAGE, and pass the vaddr to it so it > > works on MIPS and s390. > > > > Signed-off-by: Matthew Wilcox <[email protected]> > > I'm being thick and / or lazy, what's the user visible effect of this fix?
For s390 it appears to be a performance issue: Author: Martin Schwidefsky <[email protected]> Date: Mon Oct 25 16:10:07 2010 +0200 [S390] zero page cache synonyms If the zero page is mapped to virtual user space addresses that differ only in bit 2^12 or 2^13 we get L1 cache synonyms which can affect performance. Follow the mips model and use multiple zero pages to avoid the synonyms. MIPS' use of multiple ZERO_PAGEs predates git history. Given the history of MIPS' caches behaving in incredibly weird ways, I'd assume that getting this wrong results in miniature black holes forming and/or the CPU calculating the largest prime number. _______________________________________________ Linux-nvdimm mailing list [email protected] https://lists.01.org/mailman/listinfo/linux-nvdimm
