On Tue 25-06-24 14:03:33, Andrew Morton wrote: > > The quilt patch titled > Subject: mm: add swappiness= arg to memory.reclaim > has been removed from the -mm tree. Its filename was > mm-add-swapiness=-arg-to-memoryreclaim.patch > > This patch was dropped because it was nacked I do not see this being nacked in the original email thread. > ------------------------------------------------------ > From: Dan Schatzberg <schatzberg.dan@xxxxxxxxx> > Subject: mm: add swappiness= arg to memory.reclaim > Date: Wed, 3 Jan 2024 08:48:37 -0800 > > Allow proactive reclaimers to submit an additional swappiness=<val> > argument to memory.reclaim. This overrides the global or per-memcg > swappiness setting for that reclaim attempt. > > For example: > > echo "2M swappiness=0" > /sys/fs/cgroup/memory.reclaim > > will perform reclaim on the rootcg with a swappiness setting of 0 (no > swap) regardless of the vm.swappiness sysctl setting. > > Userspace proactive reclaimers use the memory.reclaim interface to trigger > reclaim. The memory.reclaim interface does not allow for any way to > effect the balance of file vs anon during proactive reclaim. The only > approach is to adjust the vm.swappiness setting. However, there are a few > reasons we look to control the balance of file vs anon during proactive > reclaim, separately from reactive reclaim: > > * Swapout should be limited to manage SSD write endurance. In near-OOM > situations we are fine with lots of swap-out to avoid OOMs. As these > are typically rare events, they have relatively little impact on write > endurance. However, proactive reclaim runs continuously and so its > impact on SSD write endurance is more significant. Therefore it is > desireable to control swap-out for proactive reclaim separately from > reactive reclaim > > * Some userspace OOM killers like systemd-oomd[1] support OOM killing on > swap exhaustion. This makes sense if the swap exhaustion is triggered > due to reactive reclaim but less so if it is triggered due to proactive > reclaim (e.g. one could see OOMs when free memory is ample but anon is > just particularly cold). Therefore, it's desireable to have proactive > reclaim reduce or stop swap-out before the threshold at which OOM > killing occurs. > > In the case of Meta's Senpai proactive reclaimer, we adjust vm.swappiness > before writes to memory.reclaim[2]. This has been in production for > nearly two years and has addressed our needs to control proactive vs > reactive reclaim behavior but is still not ideal for a number of reasons: > > * vm.swappiness is a global setting, adjusting it can race/interfere > with other system administration that wishes to control vm.swappiness. > In our case, we need to disable Senpai before adjusting vm.swappiness. > > * vm.swappiness is stateful - so a crash or restart of Senpai can leave > a misconfigured setting. This requires some additional management to > record the "desired" setting and ensure Senpai always adjusts to it. > > With this patch, we avoid these downsides of adjusting vm.swappiness > globally. > > [1]https://www.freedesktop.org/software/systemd/man/latest/systemd-oomd.service.html > [2]https://github.com/facebookincubator/oomd/blob/main/src/oomd/plugins/Senpai.cpp#L585-L598 > > Link: https://lkml.kernel.org/r/20240103164841.2800183-3-schatzberg.dan@xxxxxxxxx > Signed-off-by: Dan Schatzberg <schatzberg.dan@xxxxxxxxx> > Suggested-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx> > Acked-by: Michal Hocko <mhocko@xxxxxxxx> > Acked-by: David Rientjes <rientjes@xxxxxxxxxx> > Acked-by: Chris Li <chrisl@xxxxxxxxxx> > Cc: David Hildenbrand <david@xxxxxxxxxx> > Cc: Hugh Dickins <hughd@xxxxxxxxxx> > Cc: Johannes Weiner <hannes@xxxxxxxxxxx> > Cc: Jonathan Corbet <corbet@xxxxxxx> > Cc: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> > Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> > Cc: Muchun Song <muchun.song@xxxxxxxxx> > Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx> > Cc: Shakeel Butt <shakeel.butt@xxxxxxxxx> > Cc: Shakeel Butt <shakeelb@xxxxxxxxxx> > Cc: Tejun Heo <tj@xxxxxxxxxx> > Cc: Yue Zhao <findns94@xxxxxxxxx> > Cc: Zefan Li <lizefan.x@xxxxxxxxxxxxx> > Cc: Nhat Pham <nphamcs@xxxxxxxxx> > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > --- > > Documentation/admin-guide/cgroup-v2.rst | 18 ++++-- > include/linux/swap.h | 3 - > mm/memcontrol.c | 57 +++++++++++++++++----- > mm/vmscan.c | 25 ++++++++- > 4 files changed, 81 insertions(+), 22 deletions(-) > > --- a/Documentation/admin-guide/cgroup-v2.rst~mm-add-swapiness=-arg-to-memoryreclaim > +++ a/Documentation/admin-guide/cgroup-v2.rst > @@ -1299,17 +1299,10 @@ PAGE_SIZE multiple when read back. > This is a simple interface to trigger memory reclaim in the > target cgroup. > > - This file accepts a single key, the number of bytes to reclaim. > - No nested keys are currently supported. > - > Example:: > > echo "1G" > memory.reclaim > > - The interface can be later extended with nested keys to > - configure the reclaim behavior. For example, specify the > - type of memory to reclaim from (anon, file, ..). > - > Please note that the kernel can over or under reclaim from > the target cgroup. If less bytes are reclaimed than the > specified amount, -EAGAIN is returned. > @@ -1321,6 +1314,17 @@ PAGE_SIZE multiple when read back. > This means that the networking layer will not adapt based on > reclaim induced by memory.reclaim. > > +The following nested keys are defined. > + > + ========== ================================ > + swappiness Swappiness value to reclaim with > + ========== ================================ > + > + Specifying a swappiness value instructs the kernel to perform > + the reclaim with that swappiness value. Note that this has the > + same semantics as vm.swappiness applied to memcg reclaim with > + all the existing limitations and potential future extensions. > + > memory.peak > A read-only single value file which exists on non-root > cgroups. > --- a/include/linux/swap.h~mm-add-swapiness=-arg-to-memoryreclaim > +++ a/include/linux/swap.h > @@ -410,7 +410,8 @@ extern unsigned long try_to_free_pages(s > extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg, > unsigned long nr_pages, > gfp_t gfp_mask, > - unsigned int reclaim_options); > + unsigned int reclaim_options, > + int *swappiness); > extern unsigned long mem_cgroup_shrink_node(struct mem_cgroup *mem, > gfp_t gfp_mask, bool noswap, > pg_data_t *pgdat, > --- a/mm/memcontrol.c~mm-add-swapiness=-arg-to-memoryreclaim > +++ a/mm/memcontrol.c > @@ -53,6 +53,7 @@ > #include <linux/sort.h> > #include <linux/fs.h> > #include <linux/seq_file.h> > +#include <linux/parser.h> > #include <linux/vmpressure.h> > #include <linux/memremap.h> > #include <linux/mm_inline.h> > @@ -2636,7 +2637,8 @@ static unsigned long reclaim_high(struct > psi_memstall_enter(&pflags); > nr_reclaimed += try_to_free_mem_cgroup_pages(memcg, nr_pages, > gfp_mask, > - MEMCG_RECLAIM_MAY_SWAP); > + MEMCG_RECLAIM_MAY_SWAP, > + NULL); > psi_memstall_leave(&pflags); > } while ((memcg = parent_mem_cgroup(memcg)) && > !mem_cgroup_is_root(memcg)); > @@ -2942,7 +2944,7 @@ retry: > > psi_memstall_enter(&pflags); > nr_reclaimed = try_to_free_mem_cgroup_pages(mem_over_limit, nr_pages, > - gfp_mask, reclaim_options); > + gfp_mask, reclaim_options, NULL); > psi_memstall_leave(&pflags); > > if (mem_cgroup_margin(mem_over_limit) >= nr_pages) > @@ -3911,7 +3913,7 @@ static int mem_cgroup_resize_max(struct > } > > if (!try_to_free_mem_cgroup_pages(memcg, 1, GFP_KERNEL, > - memsw ? 0 : MEMCG_RECLAIM_MAY_SWAP)) { > + memsw ? 0 : MEMCG_RECLAIM_MAY_SWAP, NULL)) { > ret = -EBUSY; > break; > } > @@ -4025,7 +4027,7 @@ static int mem_cgroup_force_empty(struct > return -EINTR; > > if (!try_to_free_mem_cgroup_pages(memcg, 1, GFP_KERNEL, > - MEMCG_RECLAIM_MAY_SWAP)) > + MEMCG_RECLAIM_MAY_SWAP, NULL)) > nr_retries--; > } > > @@ -7000,7 +7002,7 @@ static ssize_t memory_high_write(struct > } > > reclaimed = try_to_free_mem_cgroup_pages(memcg, nr_pages - high, > - GFP_KERNEL, MEMCG_RECLAIM_MAY_SWAP); > + GFP_KERNEL, MEMCG_RECLAIM_MAY_SWAP, NULL); > > if (!reclaimed && !nr_retries--) > break; > @@ -7049,7 +7051,7 @@ static ssize_t memory_max_write(struct k > > if (nr_reclaims) { > if (!try_to_free_mem_cgroup_pages(memcg, nr_pages - max, > - GFP_KERNEL, MEMCG_RECLAIM_MAY_SWAP)) > + GFP_KERNEL, MEMCG_RECLAIM_MAY_SWAP, NULL)) > nr_reclaims--; > continue; > } > @@ -7179,19 +7181,50 @@ static ssize_t memory_oom_group_write(st > return nbytes; > } > > +enum { > + MEMORY_RECLAIM_SWAPPINESS = 0, > + MEMORY_RECLAIM_NULL, > +}; > + > +static const match_table_t tokens = { > + { MEMORY_RECLAIM_SWAPPINESS, "swappiness=%d"}, > + { MEMORY_RECLAIM_NULL, NULL }, > +}; > + > static ssize_t memory_reclaim(struct kernfs_open_file *of, char *buf, > size_t nbytes, loff_t off) > { > struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of)); > unsigned int nr_retries = MAX_RECLAIM_RETRIES; > unsigned long nr_to_reclaim, nr_reclaimed = 0; > + int swappiness = -1; > unsigned int reclaim_options; > - int err; > + char *old_buf, *start; > + substring_t args[MAX_OPT_ARGS]; > > buf = strstrip(buf); > - err = page_counter_memparse(buf, "", &nr_to_reclaim); > - if (err) > - return err; > + > + old_buf = buf; > + nr_to_reclaim = memparse(buf, &buf) / PAGE_SIZE; > + if (buf == old_buf) > + return -EINVAL; > + > + buf = strstrip(buf); > + > + while ((start = strsep(&buf, " ")) != NULL) { > + if (!strlen(start)) > + continue; > + switch (match_token(start, tokens, args)) { > + case MEMORY_RECLAIM_SWAPPINESS: > + if (match_int(&args[0], &swappiness)) > + return -EINVAL; > + if (swappiness < MIN_SWAPPINESS || swappiness > MAX_SWAPPINESS) > + return -EINVAL; > + break; > + default: > + return -EINVAL; > + } > + } > > reclaim_options = MEMCG_RECLAIM_MAY_SWAP | MEMCG_RECLAIM_PROACTIVE; > while (nr_reclaimed < nr_to_reclaim) { > @@ -7211,7 +7244,9 @@ static ssize_t memory_reclaim(struct ker > lru_add_drain_all(); > > reclaimed = try_to_free_mem_cgroup_pages(memcg, > - batch_size, GFP_KERNEL, reclaim_options); > + batch_size, GFP_KERNEL, > + reclaim_options, > + swappiness == -1 ? NULL : &swappiness); > > if (!reclaimed && !nr_retries--) > return -EAGAIN; > --- a/mm/vmscan.c~mm-add-swapiness=-arg-to-memoryreclaim > +++ a/mm/vmscan.c > @@ -92,6 +92,11 @@ struct scan_control { > unsigned long anon_cost; > unsigned long file_cost; > > +#ifdef CONFIG_MEMCG > + /* Swappiness value for proactive reclaim. Always use sc_swappiness()! */ > + int *proactive_swappiness; > +#endif > + > /* Can active folios be deactivated as part of reclaim? */ > #define DEACTIVATE_ANON 1 > #define DEACTIVATE_FILE 2 > @@ -236,6 +241,13 @@ static bool writeback_throttling_sane(st > #endif > return false; > } > + > +static int sc_swappiness(struct scan_control *sc, struct mem_cgroup *memcg) > +{ > + if (sc->proactive && sc->proactive_swappiness) > + return *sc->proactive_swappiness; > + return mem_cgroup_swappiness(memcg); > +} > #else > static bool cgroup_reclaim(struct scan_control *sc) > { > @@ -251,6 +263,11 @@ static bool writeback_throttling_sane(st > { > return true; > } > + > +static int sc_swappiness(struct scan_control *sc, struct mem_cgroup *memcg) > +{ > + return READ_ONCE(vm_swappiness); > +} > #endif > > static void set_task_reclaim_state(struct task_struct *task, > @@ -2351,7 +2368,7 @@ static void get_scan_count(struct lruvec > struct pglist_data *pgdat = lruvec_pgdat(lruvec); > struct mem_cgroup *memcg = lruvec_memcg(lruvec); > unsigned long anon_cost, file_cost, total_cost; > - int swappiness = mem_cgroup_swappiness(memcg); > + int swappiness = sc_swappiness(sc, memcg); > u64 fraction[ANON_AND_FILE]; > u64 denominator = 0; /* gcc */ > enum scan_balance scan_balance; > @@ -2632,7 +2649,7 @@ static int get_swappiness(struct lruvec > mem_cgroup_get_nr_swap_pages(memcg) < MIN_LRU_BATCH) > return 0; > > - return mem_cgroup_swappiness(memcg); > + return sc_swappiness(sc, memcg); > } > > static int get_nr_gens(struct lruvec *lruvec, int type) > @@ -6549,12 +6566,14 @@ unsigned long mem_cgroup_shrink_node(str > unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg, > unsigned long nr_pages, > gfp_t gfp_mask, > - unsigned int reclaim_options) > + unsigned int reclaim_options, > + int *swappiness) > { > unsigned long nr_reclaimed; > unsigned int noreclaim_flag; > struct scan_control sc = { > .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX), > + .proactive_swappiness = swappiness, > .gfp_mask = (current_gfp_context(gfp_mask) & GFP_RECLAIM_MASK) | > (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK), > .reclaim_idx = MAX_NR_ZONES - 1, > _ > > Patches currently in -mm which might be from schatzberg.dan@xxxxxxxxx are > > -- Michal Hocko SUSE Labs
