Hi,
We looked at removing the ticks from subr_pool.c a while back but it
got shelved. That may or may not have been my fault. I don't
remember.
Anyway, I would normally suggest switching to getuptime(9) here, but
getuptime(9) counts in seconds and we're working with a 1 second
timeout in this code (pool_wait_free) so that's too coarse an
interface for this job.
The next best thing I could come up with was introducing a coarse
sub-second interface for use in this file, "getnsecuptime()", which
calls getnanouptime(9) and converts the result to a 64-bit count of
nanoseconds. This is relatively fast (we don't read the underlying
timecounter hardware) and causes a minimal amount of code change (we
can use it inline because it returns an integral value).
>From there the changes are simple:
- Renames: ph_tick -> ph_timestamp, pr_cache_tick -> pr_cache_timestamp
- Call getnsecuptime(9) wherever we read 'ticks'.
- Change pool_wait_gc and pool_wait_free to counts of nanoseconds.
They could be macros, e.g.
#define POOL_WAIT_GC 8000000000ULL
but I'll leave that for a second diff to keep things simple.
This compiles and I haven't changed any logic so I assume it isn't
broken.
We could move getnsecuptime() into kern_tc.c but it isn't used
anywhere else yet so I'm hesitant to do so.
Thoughts?
Index: kern/subr_pool.c
===================================================================
RCS file: /cvs/src/sys/kern/subr_pool.c,v
retrieving revision 1.230
diff -u -p -r1.230 subr_pool.c
--- kern/subr_pool.c 24 Jan 2020 06:31:17 -0000 1.230
+++ kern/subr_pool.c 10 Dec 2020 22:08:33 -0000
@@ -41,6 +41,7 @@
#include <sys/syslog.h>
#include <sys/sysctl.h>
#include <sys/task.h>
+#include <sys/time.h>
#include <sys/timeout.h>
#include <sys/percpu.h>
@@ -148,7 +149,7 @@ struct pool_page_header {
caddr_t ph_page; /* this page's address */
caddr_t ph_colored; /* page's colored address */
unsigned long ph_magic;
- int ph_tick;
+ uint64_t ph_timestamp; /* uptime when last modified */
};
#define POOL_MAGICBIT (1 << 3) /* keep away from perturbed low bits */
#define POOL_PHPOISON(ph) ISSET((ph)->ph_magic, POOL_MAGICBIT)
@@ -266,8 +267,18 @@ void pool_gc_sched(void *);
struct timeout pool_gc_tick = TIMEOUT_INITIALIZER(pool_gc_sched, NULL);
void pool_gc_pages(void *);
struct task pool_gc_task = TASK_INITIALIZER(pool_gc_pages, NULL);
-int pool_wait_free = 1;
-int pool_wait_gc = 8;
+uint64_t pool_wait_free = 1000000000ULL; /* nanoseconds */
+uint64_t pool_wait_gc = 8000000000ULL; /* nanoseconds */
+
+/* XXX where do I put this? */
+uint64_t
+getnsecuptime(void)
+{
+ struct timespec now;
+
+ getnanouptime(&now);
+ return TIMESPEC_TO_NSEC(&now);
+}
RBT_PROTOTYPE(phtree, pool_page_header, ph_node, phtree_compare);
@@ -797,7 +808,7 @@ pool_put(struct pool *pp, void *v)
/* is it time to free a page? */
if (pp->pr_nidle > pp->pr_maxpages &&
(ph = TAILQ_FIRST(&pp->pr_emptypages)) != NULL &&
- (ticks - ph->ph_tick) > (hz * pool_wait_free)) {
+ getnsecuptime() - ph->ph_timestamp > pool_wait_free) {
freeph = ph;
pool_p_remove(pp, freeph);
}
@@ -864,7 +875,7 @@ pool_do_put(struct pool *pp, void *v)
*/
pp->pr_nidle++;
- ph->ph_tick = ticks;
+ ph->ph_timestamp = getnsecuptime();
TAILQ_REMOVE(&pp->pr_partpages, ph, ph_entry);
TAILQ_INSERT_TAIL(&pp->pr_emptypages, ph, ph_entry);
pool_update_curpage(pp);
@@ -1566,7 +1577,7 @@ pool_gc_pages(void *null)
/* is it time to free a page? */
if (pp->pr_nidle > pp->pr_minpages &&
(ph = TAILQ_FIRST(&pp->pr_emptypages)) != NULL &&
- (ticks - ph->ph_tick) > (hz * pool_wait_gc)) {
+ getnsecuptime() - ph->ph_timestamp > pool_wait_gc) {
freeph = ph;
pool_p_remove(pp, freeph);
} else
@@ -1726,7 +1737,7 @@ pool_cache_init(struct pool *pp)
arc4random_buf(pp->pr_cache_magic, sizeof(pp->pr_cache_magic));
TAILQ_INIT(&pp->pr_cache_lists);
pp->pr_cache_nitems = 0;
- pp->pr_cache_tick = ticks;
+ pp->pr_cache_timestamp = getnsecuptime();
pp->pr_cache_items = 8;
pp->pr_cache_contention = 0;
pp->pr_cache_ngc = 0;
@@ -1829,7 +1840,7 @@ pool_cache_list_free(struct pool *pp, st
{
pool_list_enter(pp);
if (TAILQ_EMPTY(&pp->pr_cache_lists))
- pp->pr_cache_tick = ticks;
+ pp->pr_cache_timestamp = getnsecuptime();
pp->pr_cache_nitems += POOL_CACHE_ITEM_NITEMS(ci);
TAILQ_INSERT_TAIL(&pp->pr_cache_lists, ci, ci_nextl);
@@ -2006,7 +2017,7 @@ pool_cache_gc(struct pool *pp)
{
unsigned int contention, delta;
- if ((ticks - pp->pr_cache_tick) > (hz * pool_wait_gc) &&
+ if (getnsecuptime() - pp->pr_cache_timestamp > pool_wait_gc &&
!TAILQ_EMPTY(&pp->pr_cache_lists) &&
pl_enter_try(pp, &pp->pr_cache_lock)) {
struct pool_cache_item *pl = NULL;
@@ -2015,7 +2026,7 @@ pool_cache_gc(struct pool *pp)
if (pl != NULL) {
TAILQ_REMOVE(&pp->pr_cache_lists, pl, ci_nextl);
pp->pr_cache_nitems -= POOL_CACHE_ITEM_NITEMS(pl);
- pp->pr_cache_tick = ticks;
+ pp->pr_cache_timestamp = getnsecuptime();
pp->pr_cache_ngc++;
}
Index: sys/pool.h
===================================================================
RCS file: /cvs/src/sys/sys/pool.h,v
retrieving revision 1.77
diff -u -p -r1.77 pool.h
--- sys/pool.h 19 Jul 2019 09:03:03 -0000 1.77
+++ sys/pool.h 10 Dec 2020 22:08:33 -0000
@@ -201,7 +201,7 @@ struct pool {
u_int pr_cache_items; /* target list length */
u_int pr_cache_contention;
u_int pr_cache_contention_prev;
- int pr_cache_tick; /* time idle list was empty */
+ uint64_t pr_cache_timestamp; /* when idle list was empty */
int pr_cache_nout;
uint64_t pr_cache_ngc; /* # of times the gc released a list */
