On 2023/8/28 15:47, Mike Rapoport wrote:
On Fri, Aug 25, 2023 at 12:18:35PM +0100, Usama Arif wrote:
For reserved memory regions marked with this flag,
reserve_bootmem_region is not called during memmap_init_reserved_pages.
This can be used to avoid struct page initialization for
regions which won't need them, for e.g. hugepages with
HVO enabled.
Signed-off-by: Usama Arif <usama.arif@xxxxxxxxxxxxx>
---
include/linux/memblock.h | 10 ++++++++++
mm/memblock.c | 32 +++++++++++++++++++++++++++-----
2 files changed, 37 insertions(+), 5 deletions(-)
diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index f71ff9f0ec81..6d681d053880 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -40,6 +40,8 @@ extern unsigned long long max_possible_pfn;
* via a driver, and never indicated in the firmware-provided memory map as
* system RAM. This corresponds to IORESOURCE_SYSRAM_DRIVER_MANAGED in the
* kernel resource tree.
+ * @MEMBLOCK_RSRV_NOINIT_VMEMMAP: memory region for which struct pages are
+ * not initialized (only for reserved regions).
*/
enum memblock_flags {
MEMBLOCK_NONE = 0x0, /* No special request */
@@ -47,6 +49,8 @@ enum memblock_flags {
MEMBLOCK_MIRROR = 0x2, /* mirrored region */
MEMBLOCK_NOMAP = 0x4, /* don't add to kernel direct mapping */
MEMBLOCK_DRIVER_MANAGED = 0x8, /* always detected via a driver */
+ /* don't initialize struct pages associated with this reserver memory block */
+ MEMBLOCK_RSRV_NOINIT_VMEMMAP = 0x10,
The flag means that struct page shouldn't be initialized, it may be used
not only by vmemmap optimizations.
Please drop _VMEMMAP.
The area at where the struct pages located is vmemmap, I think the
"vmemap" suffix does not mean that it is for "vmemmap optimization",
it could specify the target which will not be initialized. For me,
MEMBLOCK_RSRV_NOINIT does not tell me what should not be initialized,
memblock itself or its struct page (aka vmemmap pages)? So maybe
the suffix is better to keep?
And I agree with Muchun's remarks about the comments.
};
/**
@@ -125,6 +129,7 @@ int memblock_clear_hotplug(phys_addr_t base, phys_addr_t size);
int memblock_mark_mirror(phys_addr_t base, phys_addr_t size);
int memblock_mark_nomap(phys_addr_t base, phys_addr_t size);
int memblock_clear_nomap(phys_addr_t base, phys_addr_t size);
+int memblock_reserved_mark_noinit_vmemmap(phys_addr_t base, phys_addr_t size);
memblock does not care about vmemmap, please drop _vmemmap here and below as well.
void memblock_free_all(void);
void memblock_free(void *ptr, size_t size);
@@ -259,6 +264,11 @@ static inline bool memblock_is_nomap(struct memblock_region *m)
return m->flags & MEMBLOCK_NOMAP;
}
+static inline bool memblock_is_noinit_vmemmap(struct memblock_region *m)
memblock_is_reserved_noinit please.
+{
+ return m->flags & MEMBLOCK_RSRV_NOINIT_VMEMMAP;
+}
+
static inline bool memblock_is_driver_managed(struct memblock_region *m)
{
return m->flags & MEMBLOCK_DRIVER_MANAGED;
diff --git a/mm/memblock.c b/mm/memblock.c
index 43cb4404d94c..a9782228c840 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -991,6 +991,23 @@ int __init_memblock memblock_clear_nomap(phys_addr_t base, phys_addr_t size)
return memblock_setclr_flag(&memblock.memory, base, size, 0, MEMBLOCK_NOMAP);
}
+/**
+ * memblock_reserved_mark_noinit_vmemmap - Mark a reserved memory region with flag
+ * MEMBLOCK_RSRV_NOINIT_VMEMMAP.
this should be about what marking RSRV_NOINIT does, not what flag it uses
+ * @base: the base phys addr of the region
+ * @size: the size of the region
+ *
+ * struct pages will not be initialized for reserved memory regions marked with
+ * %MEMBLOCK_RSRV_NOINIT_VMEMMAP.
+ *
+ * Return: 0 on success, -errno on failure.
+ */
+int __init_memblock memblock_reserved_mark_noinit_vmemmap(phys_addr_t base, phys_addr_t size)
+{
+ return memblock_setclr_flag(&memblock.reserved, base, size, 1,
+ MEMBLOCK_RSRV_NOINIT_VMEMMAP);
+}
+
static bool should_skip_region(struct memblock_type *type,
struct memblock_region *m,
int nid, int flags)
@@ -2107,13 +2124,18 @@ static void __init memmap_init_reserved_pages(void)
memblock_set_node(start, end, &memblock.reserved, nid);
}
- /* initialize struct pages for the reserved regions */
+ /*
+ * initialize struct pages for reserved regions that don't have
+ * the MEMBLOCK_RSRV_NOINIT_VMEMMAP flag set
+ */
for_each_reserved_mem_region(region) {
- nid = memblock_get_region_node(region);
- start = region->base;
- end = start + region->size;
+ if (!memblock_is_noinit_vmemmap(region)) {
+ nid = memblock_get_region_node(region);
+ start = region->base;
+ end = start + region->size;
- reserve_bootmem_region(start, end, nid);
+ reserve_bootmem_region(start, end, nid);
+ }
}
}
--
2.25.1
