Author: mjg
Date: Tue Jul 14 21:19:33 2020
New Revision: 363202
URL: https://svnweb.freebsd.org/changeset/base/363202
Log:
cache: make negative shrinker round robin on all lists every time
Previously it would check 4, 3, 2, 1 lists. In practice by the time
it is getting called all lists have some elements and consequently
this does not result in new evictions.
Nonetheless, the code is clearer.
Tested by: pho
Modified:
head/sys/kern/vfs_cache.c
Modified: head/sys/kern/vfs_cache.c
==============================================================================
--- head/sys/kern/vfs_cache.c Tue Jul 14 21:17:46 2020 (r363201)
+++ head/sys/kern/vfs_cache.c Tue Jul 14 21:19:33 2020 (r363202)
@@ -262,7 +262,6 @@ static u_int __read_mostly ncsize; /* the size as comp
struct nchstats nchstats; /* cache effectiveness
statistics */
static struct mtx __exclusive_cache_line ncneg_shrink_lock;
-static int shrink_list_turn;
struct neglist {
struct mtx nl_lock;
@@ -815,18 +814,18 @@ cache_negative_remove(struct namecache *ncp)
}
static void
-cache_negative_shrink_select(int start, struct namecache **ncpp,
+cache_negative_shrink_select(struct namecache **ncpp,
struct neglist **neglistpp)
{
struct neglist *neglist;
struct namecache *ncp;
- int i;
+ static u_int cycle;
+ u_int i;
*ncpp = ncp = NULL;
- neglist = NULL;
- for (i = start; i < numneglists; i++) {
- neglist = &neglists[i];
+ for (i = 0; i < numneglists; i++) {
+ neglist = &neglists[(cycle + i) % numneglists];
if (TAILQ_FIRST(&neglist->nl_list) == NULL)
continue;
mtx_lock(&neglist->nl_lock);
@@ -838,6 +837,7 @@ cache_negative_shrink_select(int start, struct namecac
*neglistpp = neglist;
*ncpp = ncp;
+ cycle++;
}
static void
@@ -870,12 +870,8 @@ cache_negative_zap_one(void)
}
mtx_unlock(&ncneg_hot.nl_lock);
- cache_negative_shrink_select(shrink_list_turn, &ncp, &neglist);
- shrink_list_turn++;
- if (shrink_list_turn == numneglists)
- shrink_list_turn = 0;
- if (ncp == NULL && shrink_list_turn == 0)
- cache_negative_shrink_select(shrink_list_turn, &ncp, &neglist);
+ cache_negative_shrink_select(&ncp, &neglist);
+
mtx_unlock(&ncneg_shrink_lock);
if (ncp == NULL)
return;
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