| Message ID | 20220516102211.41557-4-songmuchun@bytedance.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | add hugetlb_optimize_vmemmap sysctl | expand |
On Mon, May 16, 2022 at 06:22:07PM +0800, Muchun Song wrote: > We are almost running out of free slots, only one bit is available in the I would be more precise about what are we running out of. Free slots of what? > worst case (powerpc with 256k pages). However, there are still some free > slots on other architectures (e.g. x86_64 has 10 bits available, arm64 > has 8 bits available with worst case of 64K pages). We have hard coded > those numbers in code, it is inconvenient to use those bits on other > architectures except powerpc. So transfer those section flags to > enumeration to make it easy to add new section flags in the future. Also, > move SECTION_TAINT_ZONE_DEVICE into the scope of CONFIG_ZONE_DEVICE > to save a bit on non-zone-device case. > > Signed-off-by: Muchun Song <songmuchun@bytedance.com> > --- ... > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -1418,16 +1418,37 @@ extern size_t mem_section_usage_size(void); > * (equal SECTION_SIZE_BITS - PAGE_SHIFT), and the > * worst combination is powerpc with 256k pages, > * which results in PFN_SECTION_SHIFT equal 6. > - * To sum it up, at least 6 bits are available. > + * To sum it up, at least 6 bits are available on all architectures. > + * However, we can exceed 6 bits on some other architectures except > + * powerpc (e.g. 15 bits are available on x86_64, 13 bits are available > + * with the worst case of 64K pages on arm64) if we make sure the > + * exceeded bit is not applicable to powerpc. > */ > -#define SECTION_MARKED_PRESENT (1UL<<0) > -#define SECTION_HAS_MEM_MAP (1UL<<1) > -#define SECTION_IS_ONLINE (1UL<<2) > -#define SECTION_IS_EARLY (1UL<<3) > -#define SECTION_TAINT_ZONE_DEVICE (1UL<<4) > -#define SECTION_MAP_LAST_BIT (1UL<<5) > +#define ENUM_SECTION_FLAG(MAPPER) \ > + MAPPER(MARKED_PRESENT) \ > + MAPPER(HAS_MEM_MAP) \ > + MAPPER(IS_ONLINE) \ > + MAPPER(IS_EARLY) \ > + MAPPER(TAINT_ZONE_DEVICE, CONFIG_ZONE_DEVICE) \ > + MAPPER(MAP_LAST_BIT) > + > +#define __SECTION_SHIFT_FLAG_MAPPER_0(x) > +#define __SECTION_SHIFT_FLAG_MAPPER_1(x) SECTION_##x##_SHIFT, > +#define __SECTION_SHIFT_FLAG_MAPPER(x, ...) \ > + __PASTE(__SECTION_SHIFT_FLAG_MAPPER_, IS_ENABLED(__VA_ARGS__))(x) > + > +#define __SECTION_FLAG_MAPPER_0(x) > +#define __SECTION_FLAG_MAPPER_1(x) SECTION_##x = BIT(SECTION_##x##_SHIFT), > +#define __SECTION_FLAG_MAPPER(x, ...) \ > + __PASTE(__SECTION_FLAG_MAPPER_, IS_ENABLED(__VA_ARGS__))(x) > + > +enum { > + ENUM_SECTION_FLAG(__SECTION_SHIFT_FLAG_MAPPER) > + ENUM_SECTION_FLAG(__SECTION_FLAG_MAPPER) > +}; > + > #define SECTION_MAP_MASK (~(SECTION_MAP_LAST_BIT-1)) > -#define SECTION_NID_SHIFT 6 > +#define SECTION_NID_SHIFT SECTION_MAP_LAST_BIT_SHIFT Is this really worth the extra code? And it might be me that I am not familiar with all this magic, but it looks overcomplicated. Maybe some comments here and there help clarifying what it is going on here. > static inline struct page *__section_mem_map_addr(struct mem_section *section) > { > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 111684878fd9..aef3f041dec7 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -655,12 +655,18 @@ static void __meminit resize_pgdat_range(struct pglist_data *pgdat, unsigned lon > > } > > +#ifdef CONFIG_ZONE_DEVICE > static void section_taint_zone_device(unsigned long pfn) > { > struct mem_section *ms = __pfn_to_section(pfn); > > ms->section_mem_map |= SECTION_TAINT_ZONE_DEVICE; > } > +#else > +static inline void section_taint_zone_device(unsigned long pfn) > +{ > +} > +#endif > > /* > * Associate the pfn range with the given zone, initializing the memmaps > -- > 2.11.0 > >
On Tue, May 17, 2022 at 09:47:48AM +0200, Oscar Salvador wrote: > On Mon, May 16, 2022 at 06:22:07PM +0800, Muchun Song wrote: > > We are almost running out of free slots, only one bit is available in the > > I would be more precise about what are we running out of. Free slots of > what? > > > worst case (powerpc with 256k pages). However, there are still some free > > slots on other architectures (e.g. x86_64 has 10 bits available, arm64 > > has 8 bits available with worst case of 64K pages). We have hard coded > > those numbers in code, it is inconvenient to use those bits on other > > architectures except powerpc. So transfer those section flags to > > enumeration to make it easy to add new section flags in the future. Also, > > move SECTION_TAINT_ZONE_DEVICE into the scope of CONFIG_ZONE_DEVICE > > to save a bit on non-zone-device case. > > > > Signed-off-by: Muchun Song <songmuchun@bytedance.com> > > --- > ... > > --- a/include/linux/mmzone.h > > +++ b/include/linux/mmzone.h > > @@ -1418,16 +1418,37 @@ extern size_t mem_section_usage_size(void); > > * (equal SECTION_SIZE_BITS - PAGE_SHIFT), and the > > * worst combination is powerpc with 256k pages, > > * which results in PFN_SECTION_SHIFT equal 6. > > - * To sum it up, at least 6 bits are available. > > + * To sum it up, at least 6 bits are available on all architectures. > > + * However, we can exceed 6 bits on some other architectures except > > + * powerpc (e.g. 15 bits are available on x86_64, 13 bits are available > > + * with the worst case of 64K pages on arm64) if we make sure the > > + * exceeded bit is not applicable to powerpc. > > */ > > -#define SECTION_MARKED_PRESENT (1UL<<0) > > -#define SECTION_HAS_MEM_MAP (1UL<<1) > > -#define SECTION_IS_ONLINE (1UL<<2) > > -#define SECTION_IS_EARLY (1UL<<3) > > -#define SECTION_TAINT_ZONE_DEVICE (1UL<<4) > > -#define SECTION_MAP_LAST_BIT (1UL<<5) > > +#define ENUM_SECTION_FLAG(MAPPER) \ > > + MAPPER(MARKED_PRESENT) \ > > + MAPPER(HAS_MEM_MAP) \ > > + MAPPER(IS_ONLINE) \ > > + MAPPER(IS_EARLY) \ > > + MAPPER(TAINT_ZONE_DEVICE, CONFIG_ZONE_DEVICE) \ > > + MAPPER(MAP_LAST_BIT) > > + > > +#define __SECTION_SHIFT_FLAG_MAPPER_0(x) > > +#define __SECTION_SHIFT_FLAG_MAPPER_1(x) SECTION_##x##_SHIFT, > > +#define __SECTION_SHIFT_FLAG_MAPPER(x, ...) \ > > + __PASTE(__SECTION_SHIFT_FLAG_MAPPER_, IS_ENABLED(__VA_ARGS__))(x) > > + > > +#define __SECTION_FLAG_MAPPER_0(x) > > +#define __SECTION_FLAG_MAPPER_1(x) SECTION_##x = BIT(SECTION_##x##_SHIFT), > > +#define __SECTION_FLAG_MAPPER(x, ...) \ > > + __PASTE(__SECTION_FLAG_MAPPER_, IS_ENABLED(__VA_ARGS__))(x) > > + > > +enum { > > + ENUM_SECTION_FLAG(__SECTION_SHIFT_FLAG_MAPPER) > > + ENUM_SECTION_FLAG(__SECTION_FLAG_MAPPER) > > +}; > > + > > #define SECTION_MAP_MASK (~(SECTION_MAP_LAST_BIT-1)) > > -#define SECTION_NID_SHIFT 6 > > +#define SECTION_NID_SHIFT SECTION_MAP_LAST_BIT_SHIFT > > Is this really worth the extra code? And it might be me that I am not > familiar with all this magic, but it looks overcomplicated. > Maybe some comments here and there help clarifying what it is going on > here. > Yeah, it's a little complicated. All the magic aims to generate two enumeration from one MAPPER(xxx, config), one is SECTION_xxx_SHIFT, another is SECTION_xxx = BIT(SECTION_xxx_SHIFT) if the 'config' is configured. If we want to add a new flag, like the follow patch, just one line could do that. MAPPER(CANNOT_OPTIMIZE_VMEMMAP, CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP) Without those magic, we have to add 4 lines like follows to do the similar thing. #ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP SECTION_CANNOT_OPTIMIZE_VMEMMAP_SHIFT, #define SECTION_CANNOT_OPTIMIZE_VMEMMAP BIT(SECTION_CANNOT_OPTIMIZE_VMEMMAP_SHIFT) #endif I admit it is more clear but not simplified as above approach. Both two approaches are fine to me. If we choose the simplified one, I agree with you I should add more comments to explain what happens here. Thanks.
diff --git a/include/linux/kconfig.h b/include/linux/kconfig.h index 20d1079e92b4..7044032b9f42 100644 --- a/include/linux/kconfig.h +++ b/include/linux/kconfig.h @@ -10,6 +10,7 @@ #define __LITTLE_ENDIAN 1234 #endif +#define __ARG_PLACEHOLDER_ 0, #define __ARG_PLACEHOLDER_1 0, #define __take_second_arg(__ignored, val, ...) val diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index aab70355d64f..af057e20b9d7 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -1418,16 +1418,37 @@ extern size_t mem_section_usage_size(void); * (equal SECTION_SIZE_BITS - PAGE_SHIFT), and the * worst combination is powerpc with 256k pages, * which results in PFN_SECTION_SHIFT equal 6. - * To sum it up, at least 6 bits are available. + * To sum it up, at least 6 bits are available on all architectures. + * However, we can exceed 6 bits on some other architectures except + * powerpc (e.g. 15 bits are available on x86_64, 13 bits are available + * with the worst case of 64K pages on arm64) if we make sure the + * exceeded bit is not applicable to powerpc. */ -#define SECTION_MARKED_PRESENT (1UL<<0) -#define SECTION_HAS_MEM_MAP (1UL<<1) -#define SECTION_IS_ONLINE (1UL<<2) -#define SECTION_IS_EARLY (1UL<<3) -#define SECTION_TAINT_ZONE_DEVICE (1UL<<4) -#define SECTION_MAP_LAST_BIT (1UL<<5) +#define ENUM_SECTION_FLAG(MAPPER) \ + MAPPER(MARKED_PRESENT) \ + MAPPER(HAS_MEM_MAP) \ + MAPPER(IS_ONLINE) \ + MAPPER(IS_EARLY) \ + MAPPER(TAINT_ZONE_DEVICE, CONFIG_ZONE_DEVICE) \ + MAPPER(MAP_LAST_BIT) + +#define __SECTION_SHIFT_FLAG_MAPPER_0(x) +#define __SECTION_SHIFT_FLAG_MAPPER_1(x) SECTION_##x##_SHIFT, +#define __SECTION_SHIFT_FLAG_MAPPER(x, ...) \ + __PASTE(__SECTION_SHIFT_FLAG_MAPPER_, IS_ENABLED(__VA_ARGS__))(x) + +#define __SECTION_FLAG_MAPPER_0(x) +#define __SECTION_FLAG_MAPPER_1(x) SECTION_##x = BIT(SECTION_##x##_SHIFT), +#define __SECTION_FLAG_MAPPER(x, ...) \ + __PASTE(__SECTION_FLAG_MAPPER_, IS_ENABLED(__VA_ARGS__))(x) + +enum { + ENUM_SECTION_FLAG(__SECTION_SHIFT_FLAG_MAPPER) + ENUM_SECTION_FLAG(__SECTION_FLAG_MAPPER) +}; + #define SECTION_MAP_MASK (~(SECTION_MAP_LAST_BIT-1)) -#define SECTION_NID_SHIFT 6 +#define SECTION_NID_SHIFT SECTION_MAP_LAST_BIT_SHIFT static inline struct page *__section_mem_map_addr(struct mem_section *section) { diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 111684878fd9..aef3f041dec7 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -655,12 +655,18 @@ static void __meminit resize_pgdat_range(struct pglist_data *pgdat, unsigned lon } +#ifdef CONFIG_ZONE_DEVICE static void section_taint_zone_device(unsigned long pfn) { struct mem_section *ms = __pfn_to_section(pfn); ms->section_mem_map |= SECTION_TAINT_ZONE_DEVICE; } +#else +static inline void section_taint_zone_device(unsigned long pfn) +{ +} +#endif /* * Associate the pfn range with the given zone, initializing the memmaps
We are almost running out of free slots, only one bit is available in the worst case (powerpc with 256k pages). However, there are still some free slots on other architectures (e.g. x86_64 has 10 bits available, arm64 has 8 bits available with worst case of 64K pages). We have hard coded those numbers in code, it is inconvenient to use those bits on other architectures except powerpc. So transfer those section flags to enumeration to make it easy to add new section flags in the future. Also, move SECTION_TAINT_ZONE_DEVICE into the scope of CONFIG_ZONE_DEVICE to save a bit on non-zone-device case. Signed-off-by: Muchun Song <songmuchun@bytedance.com> --- include/linux/kconfig.h | 1 + include/linux/mmzone.h | 37 +++++++++++++++++++++++++++++-------- mm/memory_hotplug.c | 6 ++++++ 3 files changed, 36 insertions(+), 8 deletions(-)