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cache: make negative shrinker round robin on all lists every time

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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
This commit is contained in:
Mateusz Guzik 2020-07-14 21:19:33 +00:00
parent a110fa2ee1
commit 29f3e5ea41
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=363202
1 changed files with 8 additions and 12 deletions
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20
sys/kern/vfs_cache.c
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@ -262,7 +262,6 @@ static u_int __read_mostly ncsize; /* the size as computed on creation or resizi
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 namecache **ncpp,
*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;