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authorShakeel Butt <shakeelb@google.com>2021-02-24 12:03:55 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2021-02-24 13:38:29 -0800
commitb6038942480e574c697ea1a80019bbe586c1d654 (patch)
treee6a462f329fa8794ee9ad3d5cfef4761d7237f44 /mm/swap_state.c
parentf9b1038ebccad354256cf84749cbc321b5347497 (diff)
mm: memcg: add swapcache stat for memcg v2
This patch adds swapcache stat for the cgroup v2. The swapcache represents the memory that is accounted against both the memory and the swap limit of the cgroup. The main motivation behind exposing the swapcache stat is for enabling users to gracefully migrate from cgroup v1's memsw counter to cgroup v2's memory and swap counters. Cgroup v1's memsw limit allows users to limit the memory+swap usage of a workload but without control on the exact proportion of memory and swap. Cgroup v2 provides separate limits for memory and swap which enables more control on the exact usage of memory and swap individually for the workload. With some little subtleties, the v1's memsw limit can be switched with the sum of the v2's memory and swap limits. However the alternative for memsw usage is not yet available in cgroup v2. Exposing per-cgroup swapcache stat enables that alternative. Adding the memory usage and swap usage and subtracting the swapcache will approximate the memsw usage. This will help in the transparent migration of the workloads depending on memsw usage and limit to v2' memory and swap counters. The reasons these applications are still interested in this approximate memsw usage are: (1) these applications are not really interested in two separate memory and swap usage metrics. A single usage metric is more simple to use and reason about for them. (2) The memsw usage metric hides the underlying system's swap setup from the applications. Applications with multiple instances running in a datacenter with heterogeneous systems (some have swap and some don't) will keep seeing a consistent view of their usage. [akpm@linux-foundation.org: fix CONFIG_SWAP=n build] Link: https://lkml.kernel.org/r/20210108155813.2914586-3-shakeelb@google.com Signed-off-by: Shakeel Butt <shakeelb@google.com> Acked-by: Michal Hocko <mhocko@suse.com> Reviewed-by: Roman Gushchin <guro@fb.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Muchun Song <songmuchun@bytedance.com> Cc: Yang Shi <shy828301@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/swap_state.c')
-rw-r--r--mm/swap_state.c28
1 files changed, 2 insertions, 26 deletions
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 807b00eae969..c1a648d9092b 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -68,32 +68,6 @@ static struct {
unsigned long find_total;
} swap_cache_info;
-unsigned long total_swapcache_pages(void)
-{
- unsigned int i, j, nr;
- unsigned long ret = 0;
- struct address_space *spaces;
- struct swap_info_struct *si;
-
- for (i = 0; i < MAX_SWAPFILES; i++) {
- swp_entry_t entry = swp_entry(i, 1);
-
- /* Avoid get_swap_device() to warn for bad swap entry */
- if (!swp_swap_info(entry))
- continue;
- /* Prevent swapoff to free swapper_spaces */
- si = get_swap_device(entry);
- if (!si)
- continue;
- nr = nr_swapper_spaces[i];
- spaces = swapper_spaces[i];
- for (j = 0; j < nr; j++)
- ret += spaces[j].nrpages;
- put_swap_device(si);
- }
- return ret;
-}
-
static atomic_t swapin_readahead_hits = ATOMIC_INIT(4);
void show_swap_cache_info(void)
@@ -163,6 +137,7 @@ int add_to_swap_cache(struct page *page, swp_entry_t entry,
address_space->nrexceptional -= nr_shadows;
address_space->nrpages += nr;
__mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, nr);
+ __mod_lruvec_page_state(page, NR_SWAPCACHE, nr);
ADD_CACHE_INFO(add_total, nr);
unlock:
xas_unlock_irq(&xas);
@@ -203,6 +178,7 @@ void __delete_from_swap_cache(struct page *page,
address_space->nrexceptional += nr;
address_space->nrpages -= nr;
__mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr);
+ __mod_lruvec_page_state(page, NR_SWAPCACHE, -nr);
ADD_CACHE_INFO(del_total, nr);
}