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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200311123848.118638-1-shile.zhang@linux.alibaba.com> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 11.03.20 13:38, Shile Zhang wrote: > When 'CONFIG_DEFERRED_STRUCT_PAGE_INIT' is set, 'pgdatinit' kthread wil= l > initialise the deferred pages with local interrupts disabled. It is > introduced by commit 3a2d7fa8a3d5 ("mm: disable interrupts while > initializing deferred pages"). >=20 > On machine with NCPUS <=3D 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. >=20 > The dmesg shown that: >=20 > [ 0.197975] node 0 initialised, 32170688 pages in 1ms >=20 > Obviously, 1ms is unreasonable. >=20 > Now, fix it by restore in the pending interrupts for every 32*1204 page= s > (128MB) initialized, give the chance to update the systemd jiffies. > The reasonable demsg shown likes: >=20 > [ 1.069306] node 0 initialised, 32203456 pages in 894ms >=20 > Fixes: 3a2d7fa8a3d5 ("mm: disable interrupts while initializing deferre= d pages"). >=20 > Co-developed-by: Kirill Tkhai > Signed-off-by: Kirill Tkhai > Signed-off-by: Shile Zhang > --- > mm/page_alloc.c | 25 ++++++++++++++++++++++--- > 1 file changed, 22 insertions(+), 3 deletions(-) >=20 > 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 *zon= e, unsigned long *start_pfn, > return nr_pages; > } > =20 > +/* > + * 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 =3D data; > const struct cpumask *cpumask =3D cpumask_of_node(pgdat->node_id); > - unsigned long spfn =3D 0, epfn =3D 0, nr_pages =3D 0; > + unsigned long spfn =3D 0, epfn =3D 0, nr_pages =3D 0, prev_nr_pages =3D= 0; > unsigned long first_init_pfn, flags; > unsigned long start =3D 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); > =20 > +again: > pgdat_resize_lock(pgdat, &flags); > first_init_pfn =3D pgdat->first_deferred_pfn; > if (first_init_pfn =3D=3D 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 =3D ULONG_MAX; > =20 > /* Only the highest zone is deferred so find it */ > for (zid =3D 0; zid < MAX_NR_ZONES; zid++) { > @@ -1809,9 +1814,23 @@ static int __init deferred_init_memmap(void *dat= a) > * that we can avoid introducing any issues with the buddy > * allocator. > */ > - while (spfn < epfn) > + while (spfn < epfn) { > nr_pages +=3D 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 Nit: 128MB is only true for 4k pages. > + * system jiffies. > + */ > + if ((nr_pages - prev_nr_pages) > TICK_PAGE_COUNT) { > + prev_nr_pages =3D nr_pages; > + pgdat->first_deferred_pfn =3D spfn; > + pgdat_resize_unlock(pgdat, &flags); > + goto again; > + } > + } > + I find that deferred page init code horribly complicated to understand, but that's a different story. Your change looks sane to me and survives my basic testing. Thanks! Acked-by: David Hildenbrand --=20 Thanks, David / dhildenb