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hugetlb: batch PMD split for bulk vmemmap dedup 

In an effort to minimize amount of TLB flushes, batch all PMD splits
belonging to a range of pages in order to perform only 1 (global) TLB
flush.

Add a flags field to the walker and pass whether it's a bulk allocation or
just a single page to decide to remap.  First value
(VMEMMAP_SPLIT_NO_TLB_FLUSH) designates the request to not do the TLB
flush when we split the PMD.

Rebased and updated by Mike Kravetz

Link: https://lkml.kernel.org/r/20231019023113.345257-7-mike.kravetz@oracle.com
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Barry Song <21cnbao@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: James Houghton <jthoughton@google.com>
Cc: Konrad Dybcio <konradybcio@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Usama Arif <usama.arif@bytedance.com>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Joao Martins 2023-10-18 19:31:08 -07:00 committed by Andrew Morton
parent 91f386bf07
commit f4b7e3efad
1 changed files with 88 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

92
mm/hugetlb_vmemmap.c
View File

@ -27,6 +27,8 @@
* @reuse_addr: the virtual address of the @reuse_page page.
* @vmemmap_pages: the list head of the vmemmap pages that can be freed
* or is mapped from.
* @flags: used to modify behavior in vmemmap page table walking
* operations.
*/
struct vmemmap_remap_walk {
void (*remap_pte)(pte_t *pte, unsigned long addr,
@ -35,9 +37,13 @@ struct vmemmap_remap_walk {
struct page *reuse_page;
unsigned long reuse_addr;
struct list_head *vmemmap_pages;
/* Skip the TLB flush when we split the PMD */
#define VMEMMAP_SPLIT_NO_TLB_FLUSH BIT(0)
unsigned long flags;
};
static int split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start)
static int split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start, bool flush)
{
pmd_t __pmd;
int i;
@ -80,7 +86,8 @@ static int split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start)
/* Make pte visible before pmd. See comment in pmd_install(). */
smp_wmb();
pmd_populate_kernel(&init_mm, pmd, pgtable);
flush_tlb_kernel_range(start, start + PMD_SIZE);
if (flush)
flush_tlb_kernel_range(start, start + PMD_SIZE);
} else {
pte_free_kernel(&init_mm, pgtable);
}
@ -127,11 +134,20 @@ static int vmemmap_pmd_range(pud_t *pud, unsigned long addr,
do {
int ret;
ret = split_vmemmap_huge_pmd(pmd, addr & PMD_MASK);
ret = split_vmemmap_huge_pmd(pmd, addr & PMD_MASK,
!(walk->flags & VMEMMAP_SPLIT_NO_TLB_FLUSH));
if (ret)
return ret;
next = pmd_addr_end(addr, end);
/*
* We are only splitting, not remapping the hugetlb vmemmap
* pages.
*/
if (!walk->remap_pte)
continue;
vmemmap_pte_range(pmd, addr, next, walk);
} while (pmd++, addr = next, addr != end);
@ -198,7 +214,8 @@ static int vmemmap_remap_range(unsigned long start, unsigned long end,
return ret;
} while (pgd++, addr = next, addr != end);
flush_tlb_kernel_range(start, end);
if (walk->remap_pte)
flush_tlb_kernel_range(start, end);
return 0;
}
@ -297,6 +314,36 @@ static void vmemmap_restore_pte(pte_t *pte, unsigned long addr,
set_pte_at(&init_mm, addr, pte, mk_pte(page, pgprot));
}
/**
* vmemmap_remap_split - split the vmemmap virtual address range [@start, @end)
* backing PMDs of the directmap into PTEs
* @start: start address of the vmemmap virtual address range that we want
* to remap.
* @end: end address of the vmemmap virtual address range that we want to
* remap.
* @reuse: reuse address.
*
* Return: %0 on success, negative error code otherwise.
*/
static int vmemmap_remap_split(unsigned long start, unsigned long end,
unsigned long reuse)
{
int ret;
struct vmemmap_remap_walk walk = {
.remap_pte = NULL,
.flags = VMEMMAP_SPLIT_NO_TLB_FLUSH,
};
/* See the comment in the vmemmap_remap_free(). */
BUG_ON(start - reuse != PAGE_SIZE);
mmap_read_lock(&init_mm);
ret = vmemmap_remap_range(reuse, end, &walk);
mmap_read_unlock(&init_mm);
return ret;
}
/**
* vmemmap_remap_free - remap the vmemmap virtual address range [@start, @end)
* to the page which @reuse is mapped to, then free vmemmap
@ -320,6 +367,7 @@ static int vmemmap_remap_free(unsigned long start, unsigned long end,
.remap_pte = vmemmap_remap_pte,
.reuse_addr = reuse,
.vmemmap_pages = vmemmap_pages,
.flags = 0,
};
int nid = page_to_nid((struct page *)reuse);
gfp_t gfp_mask = GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN;
@ -368,6 +416,7 @@ static int vmemmap_remap_free(unsigned long start, unsigned long end,
.remap_pte = vmemmap_restore_pte,
.reuse_addr = reuse,
.vmemmap_pages = vmemmap_pages,
.flags = 0,
};
vmemmap_remap_range(reuse, end, &walk);
@ -419,6 +468,7 @@ static int vmemmap_remap_alloc(unsigned long start, unsigned long end,
.remap_pte = vmemmap_restore_pte,
.reuse_addr = reuse,
.vmemmap_pages = &vmemmap_pages,
.flags = 0,
};
/* See the comment in the vmemmap_remap_free(). */
@ -628,11 +678,45 @@ void hugetlb_vmemmap_optimize(const struct hstate *h, struct page *head)
free_vmemmap_page_list(&vmemmap_pages);
}
static int hugetlb_vmemmap_split(const struct hstate *h, struct page *head)
{
unsigned long vmemmap_start = (unsigned long)head, vmemmap_end;
unsigned long vmemmap_reuse;
if (!vmemmap_should_optimize(h, head))
return 0;
vmemmap_end = vmemmap_start + hugetlb_vmemmap_size(h);
vmemmap_reuse = vmemmap_start;
vmemmap_start += HUGETLB_VMEMMAP_RESERVE_SIZE;
/*
* Split PMDs on the vmemmap virtual address range [@vmemmap_start,
* @vmemmap_end]
*/
return vmemmap_remap_split(vmemmap_start, vmemmap_end, vmemmap_reuse);
}
void hugetlb_vmemmap_optimize_folios(struct hstate *h, struct list_head *folio_list)
{
struct folio *folio;
LIST_HEAD(vmemmap_pages);
list_for_each_entry(folio, folio_list, lru) {
int ret = hugetlb_vmemmap_split(h, &folio->page);
/*
* Spliting the PMD requires allocating a page, thus lets fail
* early once we encounter the first OOM. No point in retrying
* as it can be dynamically done on remap with the memory
* we get back from the vmemmap deduplication.
*/
if (ret == -ENOMEM)
break;
}
flush_tlb_all();
list_for_each_entry(folio, folio_list, lru) {
int ret = __hugetlb_vmemmap_optimize(h, &folio->page,
&vmemmap_pages);