On Thu, Jul 6, 2023 at 12:21 AM Aneesh Kumar K.V
<aneesh.kumar@xxxxxxxxxxxxx> wrote:
>
> This patchset avoids building changes added by commit bd74fdaea146 ("mm:
> multi-gen LRU: support page table walks") on platforms that don't support
> hardware atomic updates of access bits.
>
> Aneesh Kumar K.V (5):
> mm/mglru: Create a new helper iterate_mm_list_walk
> mm/mglru: Move Bloom filter code around
> mm/mglru: Move code around to make future patch easy
> mm/mglru: move iterate_mm_list_walk Helper
> mm/mglru: Don't build multi-gen LRU page table walk code on
> architecture not supported
>
> arch/Kconfig | 3 +
> arch/arm64/Kconfig | 1 +
> arch/x86/Kconfig | 1 +
> include/linux/memcontrol.h | 2 +-
> include/linux/mm_types.h | 10 +-
> include/linux/mmzone.h | 12 +-
> kernel/fork.c | 2 +-
> mm/memcontrol.c | 2 +-
> mm/vmscan.c | 955 +++++++++++++++++++------------------
> 9 files changed, 528 insertions(+), 460 deletions(-)
1. There is no need for a new Kconfig -- the condition is simply
defined(CONFIG_LRU_GEN) && !defined(arch_has_hw_pte_young)
2. The best practice to disable static functions is not by macros but:
static int const_cond(void)
{
return 1;
}
int main(void)
{
int a = const_cond();
if (a)
return 0;
/* the compiler doesn't generate code for static funcs below */
static_func_1();
...
static_func_N();
LTO also optimizes external functions. But not everyone uses it. So we
still need macros for them, and of course data structures.
3. In 4/5, you have:
@@ -461,6 +461,7 @@ enum {
struct lru_gen_mm_state {
/* set to max_seq after each iteration */
unsigned long seq;
+#ifdef CONFIG_LRU_TASK_PAGE_AGING
/* where the current iteration continues after */
struct list_head *head;
/* where the last iteration ended before */
@@ -469,6 +470,11 @@ struct lru_gen_mm_state {
unsigned long *filters[NR_BLOOM_FILTERS];
/* the mm stats for debugging */
unsigned long stats[NR_HIST_GENS][NR_MM_STATS];
+#else
+ /* protect the seq update above */
+ /* May be we can use lruvec->lock? */
+ spinlock_t lock;
+#endif
};
The answer is yes, and not only that, we don't need lru_gen_mm_state at all.
I'm attaching a patch that fixes all above. If you want to post it,
please feel free -- fully test it please, since I didn't. Otherwise I
can ask TJ to help make this work for you.
$ git diff --stat
include/linux/memcontrol.h | 2 +-
include/linux/mm_types.h | 12 +-
include/linux/mmzone.h | 2 +
kernel/bounds.c | 6 +-
kernel/fork.c | 2 +-
mm/vmscan.c | 169 +++++++++++++++++++--------
6 files changed, 137 insertions(+), 56 deletions(-)
On x86:
$ ./scripts/bloat-o-meter mm/vmscan.o.old mm/vmscan.o
add/remove: 24/34 grow/shrink: 2/7 up/down: 966/-8716 (-7750)
Function old new delta
...
should_skip_vma 206 - -206
get_pte_pfn 261 - -261
lru_gen_add_mm 323 - -323
lru_gen_seq_show 1710 1370 -340
lru_gen_del_mm 432 - -432
reset_batch_size 572 - -572
try_to_inc_max_seq 2947 1635 -1312
walk_pmd_range_locked 1508 - -1508
walk_pud_range 3238 - -3238
Total: Before=99449, After=91699, chg -7.79%
$ objdump -S mm/vmscan.o | grep -A 20 "<try_to_inc_max_seq>:"
000000000000a350 <try_to_inc_max_seq>:
{
a350: e8 00 00 00 00 call a355 <try_to_inc_max_seq+0x5>
a355: 55 push %rbp
a356: 48 89 e5 mov %rsp,%rbp
a359: 41 57 push %r15
a35b: 41 56 push %r14
a35d: 41 55 push %r13
a35f: 41 54 push %r12
a361: 53 push %rbx
a362: 48 83 ec 70 sub $0x70,%rsp
a366: 41 89 d4 mov %edx,%r12d
a369: 49 89 f6 mov %rsi,%r14
a36c: 49 89 ff mov %rdi,%r15
spin_lock_irq(&lruvec->lru_lock);
a36f: 48 8d 5f 50 lea 0x50(%rdi),%rbx
a373: 48 89 df mov %rbx,%rdi
a376: e8 00 00 00 00 call a37b <try_to_inc_max_seq+0x2b>
success = max_seq == lrugen->max_seq;
a37b: 49 8b 87 88 00 00 00 mov 0x88(%r15),%rax
a382: 4c 39 f0 cmp %r14,%rax
Attachment:
no_mm_walk.patch
Description: Binary data
