Re: [PATCH 1/2] mm/rmap: support folio_referenced to control if try_lock in rmap_walk
From: 李培锋
Date: Mon Feb 19 2024 - 23:00:26 EST
在 2024/2/20 11:01, Barry Song 写道:
Hi peifeng,
On Tue, Feb 20, 2024 at 2:43 PM 李培锋 <lipeifeng@xxxxxxxx> wrote:
add more experts from Linux and Google.
在 2024/2/19 22:17, lipeifeng@xxxxxxxx 写道:
From: lipeifeng <lipeifeng@xxxxxxxx>
The patch to support folio_referenced to control the bevavior
of walk_rmap, which for some thread to hold the lock in rmap_walk
instead of try_lock when using folio_referenced.
please describe what problem the patch is trying to address,
and why this modification is needed in commit message.
Hi Barry：
1. the patch is one of the kshrinkd series patches.
2. it is to support folio_referenced to control the bevavior of walk_rmap,
kshrinkd would call folio_referenced through shrink_folio_list but it
doesn't
want to try_lock in rmap_walk during folio_referenced.
btw, who is set rw_try_lock to 0, what is the benefit?
Actually, the current situation is that only shrink_folio_list will set
try_lock to 1，
while others will be set to 0 that it would wait for rwsem-lock if
contened in rmap_walk.
Signed-off-by: lipeifeng <lipeifeng@xxxxxxxx>
---
include/linux/rmap.h | 5 +++--
mm/rmap.c | 5 +++--
mm/vmscan.c | 16 ++++++++++++++--
3 files changed, 20 insertions(+), 6 deletions(-)
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index b7944a8..846b261 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -623,7 +623,8 @@ static inline int folio_try_share_anon_rmap_pmd(struct folio *folio,
* Called from mm/vmscan.c to handle paging out
*/
int folio_referenced(struct folio *, int is_locked,
- struct mem_cgroup *memcg, unsigned long *vm_flags);
+ struct mem_cgroup *memcg, unsigned long *vm_flags,
+ unsigned int rw_try_lock);
void try_to_migrate(struct folio *folio, enum ttu_flags flags);
void try_to_unmap(struct folio *, enum ttu_flags flags);
@@ -739,7 +740,7 @@ struct anon_vma *folio_lock_anon_vma_read(struct folio *folio,
static inline int folio_referenced(struct folio *folio, int is_locked,
struct mem_cgroup *memcg,
- unsigned long *vm_flags)
+ unsigned long *vm_flags, unsigned int rw_try_lock)
{
*vm_flags = 0;
return 0;
diff --git a/mm/rmap.c b/mm/rmap.c
index f5d43ed..15d1fba 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -952,6 +952,7 @@ static bool invalid_folio_referenced_vma(struct vm_area_struct *vma, void *arg)
* @is_locked: Caller holds lock on the folio.
* @memcg: target memory cgroup
* @vm_flags: A combination of all the vma->vm_flags which referenced the folio.
+ * @rw_try_lock: if try_lock in rmap_walk
*
* Quick test_and_clear_referenced for all mappings of a folio,
*
@@ -959,7 +960,7 @@ static bool invalid_folio_referenced_vma(struct vm_area_struct *vma, void *arg)
* the function bailed out due to rmap lock contention.
*/
int folio_referenced(struct folio *folio, int is_locked,
- struct mem_cgroup *memcg, unsigned long *vm_flags)
+ struct mem_cgroup *memcg, unsigned long *vm_flags, unsigned int rw_try_lock)
{
int we_locked = 0;
struct folio_referenced_arg pra = {
@@ -970,7 +971,7 @@ int folio_referenced(struct folio *folio, int is_locked,
.rmap_one = folio_referenced_one,
.arg = (void *)&pra,
.anon_lock = folio_lock_anon_vma_read,
- .try_lock = true,
+ .try_lock = rw_try_lock ? true : false,
.invalid_vma = invalid_folio_referenced_vma,
};
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 4f9c854..0296d48 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -136,6 +136,9 @@ struct scan_control {
/* Always discard instead of demoting to lower tier memory */
unsigned int no_demotion:1;
+ /* if try_lock in rmap_walk */
+ unsigned int rw_try_lock:1;
+
/* Allocation order */
s8 order;
@@ -827,7 +830,7 @@ static enum folio_references folio_check_references(struct folio *folio,
unsigned long vm_flags;
referenced_ptes = folio_referenced(folio, 1, sc->target_mem_cgroup,
- &vm_flags);
+ &vm_flags, sc->rw_try_lock);
referenced_folio = folio_test_clear_referenced(folio);
/*
@@ -1501,6 +1504,7 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone,
struct scan_control sc = {
.gfp_mask = GFP_KERNEL,
.may_unmap = 1,
+ .rw_try_lock = 1,
};
struct reclaim_stat stat;
unsigned int nr_reclaimed;
@@ -2038,7 +2042,7 @@ static void shrink_active_list(unsigned long nr_to_scan,
/* Referenced or rmap lock contention: rotate */
if (folio_referenced(folio, 0, sc->target_mem_cgroup,
- &vm_flags) != 0) {
+ &vm_flags, sc->rw_try_lock) != 0) {
/*
* Identify referenced, file-backed active folios and
* give them one more trip around the active list. So
@@ -2096,6 +2100,7 @@ static unsigned int reclaim_folio_list(struct list_head *folio_list,
.may_unmap = 1,
.may_swap = 1,
.no_demotion = 1,
+ .rw_try_lock = 1,
};
nr_reclaimed = shrink_folio_list(folio_list, pgdat, &sc, &dummy_stat, false);
@@ -5442,6 +5447,7 @@ static ssize_t lru_gen_seq_write(struct file *file, const char __user *src,
.may_swap = true,
.reclaim_idx = MAX_NR_ZONES - 1,
.gfp_mask = GFP_KERNEL,
+ .rw_try_lock = 1,
};
buf = kvmalloc(len + 1, GFP_KERNEL);
@@ -6414,6 +6420,7 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
.may_writepage = !laptop_mode,
.may_unmap = 1,
.may_swap = 1,
+ .rw_try_lock = 1,
};
/*
@@ -6459,6 +6466,7 @@ unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg,
.may_unmap = 1,
.reclaim_idx = MAX_NR_ZONES - 1,
.may_swap = !noswap,
+ .rw_try_lock = 1,
};
WARN_ON_ONCE(!current->reclaim_state);
@@ -6503,6 +6511,7 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
.may_unmap = 1,
.may_swap = !!(reclaim_options & MEMCG_RECLAIM_MAY_SWAP),
.proactive = !!(reclaim_options & MEMCG_RECLAIM_PROACTIVE),
+ .rw_try_lock = 1,
};
/*
* Traverse the ZONELIST_FALLBACK zonelist of the current node to put
@@ -6764,6 +6773,7 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int highest_zoneidx)
.gfp_mask = GFP_KERNEL,
.order = order,
.may_unmap = 1,
+ .rw_try_lock = 1,
};
set_task_reclaim_state(current, &sc.reclaim_state);
@@ -7223,6 +7233,7 @@ unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
.may_unmap = 1,
.may_swap = 1,
.hibernation_mode = 1,
+ .rw_try_lock = 1,
};
struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
unsigned long nr_reclaimed;
@@ -7381,6 +7392,7 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in
.may_unmap = !!(node_reclaim_mode & RECLAIM_UNMAP),
.may_swap = 1,
.reclaim_idx = gfp_zone(gfp_mask),
+ .rw_try_lock = 1,
};
unsigned long pflags;
Thanks
Barry