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efi: Reduce the amount of memblock reservations for persistent allocations

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The current implementation of efi_mem_reserve_persistent() is rather
naive, in the sense that for each invocation, it creates a separate
linked list entry to describe the reservation. Since the linked list
entries themselves need to persist across subsequent kexec reboots,
every reservation created this way results in two memblock_reserve()
calls at the next boot.

On arm64 systems with 100s of CPUs, this may result in a excessive
number of memblock reservations, and needless fragmentation.

So instead, make use of the newly updated struct linux_efi_memreserve
layout to put multiple reservations into a single linked list entry.
This should get rid of the numerous tiny memblock reservations, and
effectively cut the total number of reservations in half on arm64
systems with many CPUs.

 [ mingo: build warning fix. ]

Tested-by: Marc Zyngier <[email protected]>
Signed-off-by: Ard Biesheuvel <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Arend van Spriel <[email protected]>
Cc: Bhupesh Sharma <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Eric Snowberg <[email protected]>
Cc: Hans de Goede <[email protected]>
Cc: Joe Perches <[email protected]>
Cc: Jon Hunter <[email protected]>
Cc: Julien Thierry <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Matt Fleming <[email protected]>
Cc: Nathan Chancellor <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Sai Praneeth Prakhya <[email protected]>
Cc: Sedat Dilek <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: YiFei Zhu <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
This commit is contained in:
Ard Biesheuvel 2018-11-29 18:12:29 +01:00 • committed by Ingo Molnar
commit 80424b02d4
2 changed files with 20 additions and 4 deletions
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21
drivers/firmware/efi/efi.c
View file

@ -997,8 +997,8 @@ static int __init efi_memreserve_map_root(void)
int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size)
{
struct linux_efi_memreserve *rsv;
int rsvsize = EFI_MEMRESERVE_SIZE(1);
int rc;
unsigned long prsv;
int rc, index;
if (efi_memreserve_root == (void *)ULONG_MAX)
return -ENODEV;
@ -1009,11 +1009,24 @@ int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size)
return rc;
}
rsv = kmalloc(rsvsize, GFP_ATOMIC);
/* first try to find a slot in an existing linked list entry */
for (prsv = efi_memreserve_root->next; prsv; prsv = rsv->next) {
rsv = __va(prsv);
index = atomic_fetch_add_unless(&rsv->count, 1, rsv->size);
if (index < rsv->size) {
rsv->entry[index].base = addr;
rsv->entry[index].size = size;
return 0;
}
}
/* no slot found - allocate a new linked list entry */
rsv = (struct linux_efi_memreserve *)__get_free_page(GFP_ATOMIC);
if (!rsv)
return -ENOMEM;
rsv->size = 1;
rsv->size = EFI_MEMRESERVE_COUNT(PAGE_SIZE);
atomic_set(&rsv->count, 1);
rsv->entry[0].base = addr;
rsv->entry[0].size = size;