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x86/mm: Simplify enabling direct_gbpages

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direct_gbpages can be force enabled as an early parameter
but not really have taken effect when DEBUG_PAGEALLOC
or KMEMCHECK is enabled. You can also enable direct_gbpages
right now if you have an x86_64 architecture but your CPU
doesn't really have support for this feature. In both cases
PG_LEVEL_1G won't actually be enabled but direct_gbpages is used
in other areas under the assumptions that PG_LEVEL_1G
was set. Fix this by putting together all requirements
which make this feature sensible to enable under, and only
enable both finally flipping on PG_LEVEL_1G and leaving
PG_LEVEL_1G set when this is true.

We only enable this feature then to be possible on sensible
builds defined by the new ENABLE_DIRECT_GBPAGES. If the
CPU has support for it you can either enable this by using
the DIRECT_GBPAGES option or using the early kernel parameter.
If a platform had support for this you can always force disable
it as well.

Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Dexuan Cui <decui@microsoft.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: JBeulich@suse.com
Cc: Jan Beulich <JBeulich@suse.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Lindgren <tony@atomide.com>
Cc: Toshi Kani <toshi.kani@hp.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Cc: julia.lawall@lip6.fr
Link: http://lkml.kernel.org/r/1425518654-3403-3-git-send-email-mcgrof@do-not-panic.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Luis R. Rodriguez 2015-03-04 17:24:12 -08:00 committed by Ingo Molnar
parent d9fd579c21
commit e5008abe92
3 changed files with 22 additions and 15 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

16
arch/x86/Kconfig
View file

@ -1299,14 +1299,22 @@ config ARCH_DMA_ADDR_T_64BIT
def_bool y
depends on X86_64 || HIGHMEM64G
config ENABLE_DIRECT_GBPAGES
def_bool y
depends on X86_64 && !DEBUG_PAGEALLOC && !KMEMCHECK
config DIRECT_GBPAGES
bool "Enable 1GB pages for kernel pagetables" if EXPERT
default y
depends on X86_64
depends on ENABLE_DIRECT_GBPAGES
---help---
Allow the kernel linear mapping to use 1GB pages on CPUs that
support it. This can improve the kernel's performance a tiny bit by
reducing TLB pressure. If in doubt, say "Y".
Enable by default the kernel linear mapping to use 1GB pages on CPUs
that support it. This can improve the kernel's performance a tiny bit
by reducing TLB pressure. If in doubt, say "Y". If you've disabled
option but your platform is capable of handling support for this
you can use the gbpages kernel parameter. Likewise if you've enabled
this but you'd like to force disable this option you can use the
nogbpages kernel parameter.
# Common NUMA Features
config NUMA

19
arch/x86/mm/init.c
View file

@ -131,16 +131,21 @@ void __init early_alloc_pgt_buf(void)
int after_bootmem;
static int page_size_mask;
int direct_gbpages = IS_ENABLED(CONFIG_DIRECT_GBPAGES);
static void __init init_gbpages(void)
{
#ifdef CONFIG_X86_64
if (direct_gbpages && cpu_has_gbpages)
printk(KERN_INFO "Using GB pages for direct mapping\n");
else
if (!IS_ENABLED(CONFIG_ENABLE_DIRECT_GBPAGES)) {
direct_gbpages = 0;
return;
}
if (direct_gbpages && cpu_has_gbpages) {
printk(KERN_INFO "Using GB pages for direct mapping\n");
page_size_mask |= 1 << PG_LEVEL_1G;
} else
direct_gbpages = 0;
#endif
}
struct map_range {
@ -149,8 +154,6 @@ struct map_range {
unsigned page_size_mask;
};
static int page_size_mask;
static void __init probe_page_size_mask(void)
{
init_gbpages();
@ -161,8 +164,6 @@ static void __init probe_page_size_mask(void)
* This will simplify cpa(), which otherwise needs to support splitting
* large pages into small in interrupt context, etc.
*/
if (direct_gbpages)
page_size_mask |= 1 << PG_LEVEL_1G;
if (cpu_has_pse)
page_size_mask |= 1 << PG_LEVEL_2M;
#endif

2
arch/x86/mm/pageattr.c
View file

@ -81,11 +81,9 @@ void arch_report_meminfo(struct seq_file *m)
seq_printf(m, "DirectMap4M: %8lu kB\n",
direct_pages_count[PG_LEVEL_2M] << 12);
#endif
#ifdef CONFIG_X86_64
if (direct_gbpages)
seq_printf(m, "DirectMap1G: %8lu kB\n",
direct_pages_count[PG_LEVEL_1G] << 20);
#endif
}
#else
static inline void split_page_count(int level) { }