On Wed, Nov 01, 2017 at 03:14:11PM -0700, Dave Hansen wrote: > On 11/01/2017 01:54 AM, Ingo Molnar wrote: > > Beyond the inevitable cavalcade of (solvable) problems that will pop up during > > review, one major item I'd like to see addressed is runtime configurability: it > > should be possible to switch between a CR3-flushing and a regular syscall and page > > table model on the admin level, without restarting the kernel and apps. Distros > > really, really don't want to double the number of kernel variants they have. > > > > The 'Kaiser off' runtime switch doesn't have to be as efficient as > > CONFIG_KAISER=n, at least initialloy, but at minimum it should avoid the most > > expensive page table switching paths in the syscall entry codepaths. > > Due to popular demand, I went and implemented this today. It's not the > prettiest code I ever wrote, but it's pretty small. > > Just in case anyone wants to play with it, I threw a snapshot of it up here: > > > https://git.kernel.org/pub/scm/linux/kernel/git/daveh/x86-kaiser.git/log/?h=kaiser-dynamic-414rc6-20171101 > > I ran some quick tests. When CONFIG_KAISER=y, but "echo 0 > > kaiser-enabled", the tests that I ran were within the noise vs. a > vanilla kernel, and that's with *zero* optimization. It doesn't compile with KASLR enabled :P Fixup: diff --git a/arch/x86/boot/compressed/pagetable.c b/arch/x86/boot/compressed/pagetable.c index f1aa43854bed..7be5fdd77a3f 100644 --- a/arch/x86/boot/compressed/pagetable.c +++ b/arch/x86/boot/compressed/pagetable.c @@ -35,6 +35,10 @@ /* Used by pgtable.h asm code to force instruction serialization. */ unsigned long __force_order; +#ifdef CONFIG_KAISER +int kaiser_enabled = 1; +#endif + /* Used to track our page table allocation area. */ struct alloc_pgt_data { unsigned char *pgt_buf; -- Kirill A. Shutemov -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
