On Wed, Mar 11, 2020 at 8:39 AM Shile Zhang <shile.zhang@xxxxxxxxxxxxxxxxx> wrote: > > When 'CONFIG_DEFERRED_STRUCT_PAGE_INIT' is set, 'pgdatinit' kthread will > initialise the deferred pages with local interrupts disabled. It is > introduced by commit 3a2d7fa8a3d5 ("mm: disable interrupts while > initializing deferred pages"). > > On machine with NCPUS <= 2, the 'pgdatinit' kthread could be bound to > the boot CPU, which could caused the tick timer long time stall, system > jiffies not be updated in time. > > The dmesg shown that: > > [ 0.197975] node 0 initialised, 32170688 pages in 1ms > > Obviously, 1ms is unreasonable. > > Now, fix it by restore in the pending interrupts for every 32*1204 pages > (128MB) initialized, give the chance to update the systemd jiffies. > The reasonable demsg shown likes: > > [ 1.069306] node 0 initialised, 32203456 pages in 894ms Sorry for joining late to this thread. I wonder if we could use sched_clock() to print this statistics. Or not to print statistics at all? ============== diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 3c4eb750a199..5958f599aced 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1770,7 +1770,7 @@ static int __init deferred_init_memmap(void *data) const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); unsigned long spfn = 0, epfn = 0, nr_pages = 0; unsigned long first_init_pfn, flags; - unsigned long start = jiffies; + unsigned long start = sched_clock(); struct zone *zone; int zid; u64 i; @@ -1817,8 +1817,8 @@ static int __init deferred_init_memmap(void *data) /* Sanity check that the next zone really is unpopulated */ WARN_ON(++zid < MAX_NR_ZONES && populated_zone(++zone)); - pr_info("node %d initialised, %lu pages in %ums\n", - pgdat->node_id, nr_pages, jiffies_to_msecs(jiffies - start)); + pr_info("node %d initialised, %lu pages in %lldns\n", + pgdat->node_id, nr_pages, sched_clock() - start); pgdat_init_report_one_done(); return 0; ============== [ 1.245331] node 0 initialised, 10256176 pages in 373565742ns Pasha > Fixes: 3a2d7fa8a3d5 ("mm: disable interrupts while initializing deferred pages"). > > Co-developed-by: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx> > Signed-off-by: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx> > Signed-off-by: Shile Zhang <shile.zhang@xxxxxxxxxxxxxxxxx> > --- > mm/page_alloc.c | 25 ++++++++++++++++++++++--- > 1 file changed, 22 insertions(+), 3 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 3c4eb750a199..a3a47845e150 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1763,12 +1763,17 @@ deferred_init_maxorder(u64 *i, struct zone *zone, unsigned long *start_pfn, > return nr_pages; > } > > +/* > + * Release the pending interrupts for every TICK_PAGE_COUNT pages. > + */ > +#define TICK_PAGE_COUNT (32 * 1024) > + > /* Initialise remaining memory on a node */ > static int __init deferred_init_memmap(void *data) > { > pg_data_t *pgdat = data; > const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); > - unsigned long spfn = 0, epfn = 0, nr_pages = 0; > + unsigned long spfn = 0, epfn = 0, nr_pages = 0, prev_nr_pages = 0; > unsigned long first_init_pfn, flags; > unsigned long start = jiffies; > struct zone *zone; > @@ -1779,6 +1784,7 @@ static int __init deferred_init_memmap(void *data) > if (!cpumask_empty(cpumask)) > set_cpus_allowed_ptr(current, cpumask); > > +again: > pgdat_resize_lock(pgdat, &flags); > first_init_pfn = pgdat->first_deferred_pfn; > if (first_init_pfn == ULONG_MAX) { > @@ -1790,7 +1796,6 @@ static int __init deferred_init_memmap(void *data) > /* Sanity check boundaries */ > BUG_ON(pgdat->first_deferred_pfn < pgdat->node_start_pfn); > BUG_ON(pgdat->first_deferred_pfn > pgdat_end_pfn(pgdat)); > - pgdat->first_deferred_pfn = ULONG_MAX; > > /* Only the highest zone is deferred so find it */ > for (zid = 0; zid < MAX_NR_ZONES; zid++) { > @@ -1809,9 +1814,23 @@ static int __init deferred_init_memmap(void *data) > * that we can avoid introducing any issues with the buddy > * allocator. > */ > - while (spfn < epfn) > + while (spfn < epfn) { > nr_pages += deferred_init_maxorder(&i, zone, &spfn, &epfn); > + /* > + * Release the interrupts for every TICK_PAGE_COUNT pages > + * (128MB) to give tick timer the chance to update the > + * system jiffies. > + */ > + if ((nr_pages - prev_nr_pages) > TICK_PAGE_COUNT) { > + prev_nr_pages = nr_pages; > + pgdat->first_deferred_pfn = spfn; > + pgdat_resize_unlock(pgdat, &flags); > + goto again; > + } > + } > + > zone_empty: > + pgdat->first_deferred_pfn = ULONG_MAX; > pgdat_resize_unlock(pgdat, &flags); > > /* Sanity check that the next zone really is unpopulated */ > -- > 2.24.0.rc2 >