| Message ID | 20240219141703.3851-1-lipeifeng@oppo.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | Support kshrinkd | expand |
On Mon, Feb 19, 2024 at 10:17:01PM +0800, lipeifeng@oppo.com wrote: > 'commit 6d4675e60135 ("mm: don't be stuck to rmap lock on reclaim path")' > The above patch would avoid reclaim path to stuck rmap lock. > But it would cause some folios in LRU not sorted by aging because > the contended-folios in rmap_walk would be putbacked to the head of LRU > during shrink_folio_list even if the folios are very cold. > > The patchset setups new kthread:kshrinkd to reclaim the contended-folio > in rmap_walk when shrink_folio_list, to avoid to break the rules of LRU. Patch 1/2 didn't make it to my inbox or to lore. But you should talk about the real world consequences of this in the cover letter. What do we observe if this problem happens? How much extra performance will we gain by applying this patch?
add more experts from Linux and Google. 在 2024/2/19 22:17, lipeifeng@oppo.com 写道: > From: lipeifeng <lipeifeng@oppo.com> > > 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. > > Signed-off-by: lipeifeng <lipeifeng@oppo.com> > --- > 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; >
在 2024/2/20 0:51, Matthew Wilcox 写道: > On Mon, Feb 19, 2024 at 10:17:01PM +0800, lipeifeng@oppo.com wrote: >> 'commit 6d4675e60135 ("mm: don't be stuck to rmap lock on reclaim path")' >> The above patch would avoid reclaim path to stuck rmap lock. >> But it would cause some folios in LRU not sorted by aging because >> the contended-folios in rmap_walk would be putbacked to the head of LRU >> during shrink_folio_list even if the folios are very cold. >> >> The patchset setups new kthread:kshrinkd to reclaim the contended-folio >> in rmap_walk when shrink_folio_list, to avoid to break the rules of LRU. > Patch 1/2 didn't make it to my inbox or to lore. Hi Sir, I had resent to you. > But you should talk > about the real world consequences of this in the cover letter. What do > we observe if this problem happens? How much extra performance will we > gain by applying this patch? Hi Sir: Monkey-test in phone with 16G-ram for 300 hours shows that almost one-third of the contended-pages can be freed successfully next time, putting back those folios to LRU's head would break the rules of inative-LRU. - pgsteal_kshrinkd 262577 - pgscan_kshrinkd 795503 "pgsteal_kshrinkd" means that the amount of those contended-folios which can be freed successfully but be putbacked in the head of inactive-LRU, more than 1GB(262577 folios). Mobile-phone with 16-ram, the total amount of inactive are around 4.5G, so that the contended-folios would break the rules of inactive-LRU. - nr_inactive_anon 1020953 - nr_inactive_file 204801 Actually, The patchset had been merged in Google kernel/common since android12-5.10 and android13-5.15, and were taken in more than 100 millions android-phone devices more than 1.5 years. But for the reason of GKI, the patches were implemented in the form of hooks, the patches merged in google-line as follows: https://android-review.googlesource.com/c/kernel/common/+/2163904 https://android-review.googlesource.com/c/kernel/common/+/2191343 https://android-review.googlesource.com/c/kernel/common/+/2550490 https://android-review.googlesource.com/c/kernel/common/+/2318311
add experts from Linux and Google. 在 2024/2/19 22:17, lipeifeng@oppo.com 写道: > From: lipeifeng <lipeifeng@oppo.com> > > 'commit 6d4675e60135 ("mm: don't be stuck to rmap lock on reclaim path")' > The above patch would avoid reclaim path to stuck rmap lock. > But it would cause some folios in LRU not sorted by aging because > the contended-folios in rmap_walk would be putbacked to the head of LRU > during shrink_folio_list even if the folios are very cold. > > The patchset setups new kthread:kshrinkd to reclaim the contended-folio > in rmap_walk when shrink_folio_list, to avoid to break the rules of LRU. > > lipeifeng (2): > mm/rmap: support folio_referenced to control if try_lock in rmap_walk > mm: support kshrinkd > > include/linux/mmzone.h | 6 ++ > include/linux/rmap.h | 5 +- > include/linux/swap.h | 3 + > include/linux/vm_event_item.h | 2 + > mm/memory_hotplug.c | 2 + > mm/rmap.c | 5 +- > mm/vmscan.c | 205 ++++++++++++++++++++++++++++++++++++++++-- > mm/vmstat.c | 2 + > 8 files changed, 221 insertions(+), 9 deletions(-) >
On Tue, Feb 20, 2024 at 10:04:33AM +0800, 李培锋 wrote: > Monkey-test in phone with 16G-ram for 300 hours shows that almost one-third > > of the contended-pages can be freed successfully next time, putting back > those > > folios to LRU's head would break the rules of inative-LRU. You talk about "the rules of inactive LRU" like we care. The LRU is an approximation at best. What are the *consequences*? Is there a benchmark that executes more operations per second as a result of this patch?
Hi peifeng, On Tue, Feb 20, 2024 at 2:43 PM 李培锋 <lipeifeng@oppo.com> wrote: > > add more experts from Linux and Google. > > > 在 2024/2/19 22:17, lipeifeng@oppo.com 写道: > > From: lipeifeng <lipeifeng@oppo.com> > > > > 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. btw, who is set rw_try_lock to 0, what is the benefit? > > > > Signed-off-by: lipeifeng <lipeifeng@oppo.com> > > --- > > 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
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@oppo.com> wrote: >> add more experts from Linux and Google. >> >> >> 在 2024/2/19 22:17, lipeifeng@oppo.com 写道: >>> From: lipeifeng <lipeifeng@oppo.com> >>> >>> 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@oppo.com> >>> --- >>> 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
在 2024/2/20 10:55, Matthew Wilcox 写道: > On Tue, Feb 20, 2024 at 10:04:33AM +0800, 李培锋 wrote: >> Monkey-test in phone with 16G-ram for 300 hours shows that almost one-third >> >> of the contended-pages can be freed successfully next time, putting back >> those >> >> folios to LRU's head would break the rules of inative-LRU. > You talk about "the rules of inactive LRU" like we care. The LRU is > an approximation at best. What are the *consequences*? > Is there a > benchmark that executes more operations per second as a result of > this patch? Hi Sir： 1. For the above data in 300 hours test in 16G-ram device: - 795503 folios would be passed during shrink_folio_list since lock contended; - 262577 folios would be reclaimed successfully but putback in head of inative-lru. 2. Converted to per second,: - 0.243 folios would be putback in the head of inative-lru mistakenly 3. issues: There are two issues with the current situation: 1. some cold-pages would not be freed in time, like the date we got in 16GB-devices almost 1GB-folios would not be freed in time during the test, which would cause shrink_folio_list to become inefficient. Especially for some folios, which are very cold and correspond to a common virtual memory space, we had found some cases that more than 20 folios were contended in rmap_walk and putback in the head of inactive-LRU during one shrink_folio_list proccess(isolate 32 folios) and more background user-process was killed by lmkd. Kshrinkd would let reclaim-path more efficient, and reduce 2% lmkd rate. 2. another issue is that staying more cold folios at the head of inative-lru would result in some hot-pages to be reclaimed, and more file-refault and anon-swapin. Data would be updated soon if need.
On Tue, Feb 20, 2024 at 5:00 PM 李培锋 <lipeifeng@oppo.com> wrote: > > > 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@oppo.com> wrote: > >> add more experts from Linux and Google. > >> > >> > >> 在 2024/2/19 22:17, lipeifeng@oppo.com 写道: > >>> From: lipeifeng <lipeifeng@oppo.com> > >>> > >>> 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. this seems like a bad name for the patchset as nobody knows what is kshrinkd. maybe something like "asynchronously reclaim contended folios rather than aging them"? > > 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， understood, as you don't want contended folios to be skipped by scanner any more. > > while others will be set to 0 that it would wait for rwsem-lock if > contened in rmap_walk. ok. other reclamation threads will still skip contended folios. As discussed, the patchset really needs detailed data to back up. Thanks Barry
From: lipeifeng <lipeifeng@oppo.com> 'commit 6d4675e60135 ("mm: don't be stuck to rmap lock on reclaim path")' The above patch would avoid reclaim path to stuck rmap lock. But it would cause some folios in LRU not sorted by aging because the contended-folios in rmap_walk would be putbacked to the head of LRU during shrink_folio_list even if the folios are very cold. The patchset setups new kthread:kshrinkd to reclaim the contended-folio in rmap_walk when shrink_folio_list, to avoid to break the rules of LRU. lipeifeng (2): mm/rmap: support folio_referenced to control if try_lock in rmap_walk mm: support kshrinkd include/linux/mmzone.h | 6 ++ include/linux/rmap.h | 5 +- include/linux/swap.h | 3 + include/linux/vm_event_item.h | 2 + mm/memory_hotplug.c | 2 + mm/rmap.c | 5 +- mm/vmscan.c | 205 ++++++++++++++++++++++++++++++++++++++++-- mm/vmstat.c | 2 + 8 files changed, 221 insertions(+), 9 deletions(-)