On 11/12/20(Fri) 12:52, Mark Kettenis wrote:
> > Date: Thu, 10 Dec 2020 16:13:22 -0600
> > From: Scott Cheloha <scottchel...@gmail.com>
> >
> > 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?
>
> Specifying the timeouts in nanoseconds isn't particularly useful I'd
> say. But I see we can't use SEC_TO_NSEC here because of the overflow
> check...
I'm not sure to understand, can't we do:
pool_wait_free = SEC_TO_NSEC(1);
pool_wait_gc = SEC_TO_NSEC(8);
or are you pointing at something else?
One comment below
> > 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;
Do you see a change in of size in the struct? If so, does moving
`pr_cache_nout' after `pr_cache_ngc' helps?
> > uint64_t pr_cache_ngc; /* # of times the gc released a list */
> >
> >
