The patch titled Subject: mm,slub,x86: decouple size of struct page from CONFIG_CMPXCHG_LOCAL has been added to the -mm tree. Its filename is mmslubx86-decouple-size-of-struct-page-from-config_cmpxchg_local.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ From: Heiko Carstens <heiko.carstens@xxxxxxxxxx> Subject: mm,slub,x86: decouple size of struct page from CONFIG_CMPXCHG_LOCAL While implementing cmpxchg_double() on s390 I realized that we don't set CONFIG_CMPXCHG_LOCAL besides the fact that we have support for it. However setting that option will increase the size of struct page by eight bytes on 64 bit, which we certainly do not want. Also, it doesn't make sense that a present cpu feature should increase the size of struct page. Besides that it looks like the dependency to CMPXCHG_LOCAL is wrong and that it should depend on CMPXCHG_DOUBLE instead. This patch: If an architecture supports CMPXCHG_LOCAL this shouldn't result automatically in larger struct pages if the SLUB allocator is used. Instead introduce a new config option "HAVE_ALIGNED_STRUCT_PAGE" which can be selected if a double word aligned struct page is required. Also update x86 Kconfig so that it should work as before. Signed-off-by: Heiko Carstens <heiko.carstens@xxxxxxxxxx> Acked-by: Christoph Lameter <cl@xxxxxxxxx> Cc: Pekka Enberg <penberg@xxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- arch/Kconfig | 8 ++++++++ arch/x86/Kconfig | 1 + include/linux/mm_types.h | 9 ++++----- mm/slub.c | 6 +++--- 4 files changed, 16 insertions(+), 8 deletions(-) diff -puN arch/Kconfig~mmslubx86-decouple-size-of-struct-page-from-config_cmpxchg_local arch/Kconfig --- a/arch/Kconfig~mmslubx86-decouple-size-of-struct-page-from-config_cmpxchg_local +++ a/arch/Kconfig @@ -185,4 +185,12 @@ config HAVE_RCU_TABLE_FREE config ARCH_HAVE_NMI_SAFE_CMPXCHG bool +config HAVE_ALIGNED_STRUCT_PAGE + bool + help + This makes sure that struct pages are double word aligned and that + e.g. the SLUB allocator can perform double word atomic operations + on a struct page for better performance. However selecting this + might increase the size of a struct page by a word. + source "kernel/gcov/Kconfig" diff -puN arch/x86/Kconfig~mmslubx86-decouple-size-of-struct-page-from-config_cmpxchg_local arch/x86/Kconfig --- a/arch/x86/Kconfig~mmslubx86-decouple-size-of-struct-page-from-config_cmpxchg_local +++ a/arch/x86/Kconfig @@ -76,6 +76,7 @@ config X86 select HAVE_BPF_JIT if (X86_64 && NET) select CLKEVT_I8253 select ARCH_HAVE_NMI_SAFE_CMPXCHG + select HAVE_ALIGNED_STRUCT_PAGE if SLUB && !M386 config INSTRUCTION_DECODER def_bool (KPROBES || PERF_EVENTS) diff -puN include/linux/mm_types.h~mmslubx86-decouple-size-of-struct-page-from-config_cmpxchg_local include/linux/mm_types.h --- a/include/linux/mm_types.h~mmslubx86-decouple-size-of-struct-page-from-config_cmpxchg_local +++ a/include/linux/mm_types.h @@ -151,12 +151,11 @@ struct page { #endif } /* - * If another subsystem starts using the double word pairing for atomic - * operations on struct page then it must change the #if to ensure - * proper alignment of the page struct. + * The struct page can be forced to be double word aligned so that atomic ops + * on double words work. The SLUB allocator can make use of such a feature. */ -#if defined(CONFIG_SLUB) && defined(CONFIG_CMPXCHG_LOCAL) - __attribute__((__aligned__(2*sizeof(unsigned long)))) +#ifdef CONFIG_HAVE_ALIGNED_STRUCT_PAGE + __aligned(2 * sizeof(unsigned long)) #endif ; diff -puN mm/slub.c~mmslubx86-decouple-size-of-struct-page-from-config_cmpxchg_local mm/slub.c --- a/mm/slub.c~mmslubx86-decouple-size-of-struct-page-from-config_cmpxchg_local +++ a/mm/slub.c @@ -366,7 +366,7 @@ static inline bool __cmpxchg_double_slab const char *n) { VM_BUG_ON(!irqs_disabled()); -#ifdef CONFIG_CMPXCHG_DOUBLE +#if defined(CONFIG_CMPXCHG_DOUBLE) && defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE) if (s->flags & __CMPXCHG_DOUBLE) { if (cmpxchg_double(&page->freelist, freelist_old, counters_old, @@ -400,7 +400,7 @@ static inline bool cmpxchg_double_slab(s void *freelist_new, unsigned long counters_new, const char *n) { -#ifdef CONFIG_CMPXCHG_DOUBLE +#if defined(CONFIG_CMPXCHG_DOUBLE) && defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE) if (s->flags & __CMPXCHG_DOUBLE) { if (cmpxchg_double(&page->freelist, freelist_old, counters_old, @@ -2990,7 +2990,7 @@ static int kmem_cache_open(struct kmem_c } } -#ifdef CONFIG_CMPXCHG_DOUBLE +#if defined(CONFIG_CMPXCHG_DOUBLE) && defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE) if (system_has_cmpxchg_double() && (s->flags & SLAB_DEBUG_FLAGS) == 0) /* Enable fast mode */ s->flags |= __CMPXCHG_DOUBLE; _ Subject: Subject: mm,slub,x86: decouple size of struct page from CONFIG_CMPXCHG_LOCAL Patches currently in -mm which might be from heiko.carstens@xxxxxxxxxx are linux-next.patch consolidate-config_debug_strict_user_copy_checks.patch treewide-remove-useless-noret_type-macro-and-uses.patch treewide-convert-uses-of-attrib_noreturn-to-__noreturn.patch mmslubx86-decouple-size-of-struct-page-from-config_cmpxchg_local.patch mmx86um-move-cmpxchg_local-config-option.patch mmx86um-move-cmpxchg_double-config-option.patch kdump-fix-crash_kexec-smp_send_stop-race-in-panic.patch kdump-add-udev-events-for-memory-online-offline.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html