mm/damon/reclaim: add a parameter called skip_anon for avoiding anonymous pages recla...

In some cases, for example if users have confidence at anonymous pages
management or the swap device is too slow, users would want to avoid
DAMON_RECLAIM swapping the anonymous pages out.  For such case, add yet
another DAMON_RECLAIM parameter, namely 'skip_anon'.  When it is set as
'Y', DAMON_RECLAIM will avoid reclaiming anonymous pages using a DAMOS
filter.

Link: https://lkml.kernel.org/r/20221205230830.144349-4-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/damon/reclaim.c b/mm/damon/reclaim.c
index e82631f394816f326b4d7da36f7703722058a099..648d2a85523abe613690c9890fd0729cd5a21a40 100644 (file)
--- a/mm/damon/reclaim.c
+++ b/mm/damon/reclaim.c
@@ -98,6 +98,15 @@ module_param(monitor_region_start, ulong, 0600);
 static unsigned long monitor_region_end __read_mostly;
 module_param(monitor_region_end, ulong, 0600);
 
+/*
+ * Skip anonymous pages reclamation.
+ *
+ * If this parameter is set as ``Y``, DAMON_RECLAIM does not reclaim anonymous
+ * pages.  By default, ``N``.
+ */
+static bool skip_anon __read_mostly;
+module_param(skip_anon, bool, 0600);
+
 /*
  * PID of the DAMON thread
  *
@@ -142,6 +151,7 @@ static struct damos *damon_reclaim_new_scheme(void)
 static int damon_reclaim_apply_parameters(void)
 {
        struct damos *scheme;
+       struct damos_filter *filter;
        int err = 0;
 
        err = damon_set_attrs(ctx, &damon_reclaim_mon_attrs);
@@ -152,6 +162,15 @@ static int damon_reclaim_apply_parameters(void)
        scheme = damon_reclaim_new_scheme();
        if (!scheme)
                return -ENOMEM;
+       if (skip_anon) {
+               filter = damos_new_filter(DAMOS_FILTER_TYPE_ANON, true);
+               if (!filter) {
+                       /* Will be freed by next 'damon_set_schemes()' below */
+                       damon_destroy_scheme(scheme);
+                       return -ENOMEM;
+               }
+               damos_add_filter(scheme, filter);
+       }
        damon_set_schemes(ctx, &scheme, 1);
 
        return damon_set_region_biggest_system_ram_default(target,