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| author | Xunlei Pang <xlpang@redhat.com> | 2017-05-04 04:42:50 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-05-08 09:28:40 +0300 |
| commit | 66aad4fdf2bf0af29c7decb4433dc5ec6c7c5451 (patch) | |
| tree | 9d9f1c6be69c3a4398575b6c52523042e5e9c9f1 /arch/x86/include/asm | |
| parent | 60854a12d281e2fa25662fa32ac8022bbff17432 (diff) | |
| download | linux-66aad4fdf2bf0af29c7decb4433dc5ec6c7c5451.tar.xz | |
x86/mm: Add support for gbpages to kernel_ident_mapping_init()
Kernel identity mappings on x86-64 kernels are created in two
ways: by the early x86 boot code, or by kernel_ident_mapping_init().
Native kernels (which is the dominant usecase) use the former,
but the kexec and the hibernation code uses kernel_ident_mapping_init().
There's a subtle difference between these two ways of how identity
mappings are created, the current kernel_ident_mapping_init() code
creates identity mappings always using 2MB page(PMD level) - while
the native kernel boot path also utilizes gbpages where available.
This difference is suboptimal both for performance and for memory
usage: kernel_ident_mapping_init() needs to allocate pages for the
page tables when creating the new identity mappings.
This patch adds 1GB page(PUD level) support to kernel_ident_mapping_init()
to address these concerns.
The primary advantage would be better TLB coverage/performance,
because we'd utilize 1GB TLBs instead of 2MB ones.
It is also useful for machines with large number of memory to
save paging structure allocations(around 4MB/TB using 2MB page)
when setting identity mappings for all the memory, after using
1GB page it will consume only 8KB/TB.
( Note that this change alone does not activate gbpages in kexec,
we are doing that in a separate patch. )
Signed-off-by: Xunlei Pang <xlpang@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: akpm@linux-foundation.org
Cc: kexec@lists.infradead.org
Link: http://lkml.kernel.org/r/1493862171-8799-1-git-send-email-xlpang@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/include/asm')
| -rw-r--r-- | arch/x86/include/asm/init.h | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/x86/include/asm/init.h b/arch/x86/include/asm/init.h index 737da62bfeb0..474eb8c66fee 100644 --- a/arch/x86/include/asm/init.h +++ b/arch/x86/include/asm/init.h @@ -4,8 +4,9 @@ struct x86_mapping_info { void *(*alloc_pgt_page)(void *); /* allocate buf for page table */ void *context; /* context for alloc_pgt_page */ - unsigned long pmd_flag; /* page flag for PMD entry */ + unsigned long page_flag; /* page flag for PMD or PUD entry */ unsigned long offset; /* ident mapping offset */ + bool direct_gbpages; /* PUD level 1GB page support */ }; int kernel_ident_mapping_init(struct x86_mapping_info *info, pgd_t *pgd_page, |