linux-kernel - Re: [PATCH v4 03/10] mm: apply per-task gfp constraints in fast path

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Date:   Fri, 18 Dec 2020 07:23:00 -0500
From:   Pavel Tatashin <pasha.tatashin@...een.com>
To:     Michal Hocko <mhocko@...e.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        David Hildenbrand <david@...hat.com>,
        Oscar Salvador <osalvador@...e.de>,
        Dan Williams <dan.j.williams@...el.com>,
        Sasha Levin <sashal@...nel.org>,
        Tyler Hicks <tyhicks@...ux.microsoft.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>, mike.kravetz@...cle.com,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>, Jason Gunthorpe <jgg@...pe.ca>,
        Peter Zijlstra <peterz@...radead.org>,
        Mel Gorman <mgorman@...e.de>,
        Matthew Wilcox <willy@...radead.org>,
        David Rientjes <rientjes@...gle.com>,
        John Hubbard <jhubbard@...dia.com>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        Ira Weiny <ira.weiny@...el.com>,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v4 03/10] mm: apply per-task gfp constraints in fast path

On Fri, Dec 18, 2020 at 4:36 AM Michal Hocko <mhocko@...e.com> wrote:
>
> On Thu 17-12-20 13:52:36, Pavel Tatashin wrote:
> [..]
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index 469016222cdb..d9546f5897f4 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -3234,11 +3234,12 @@ static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist,
> >  unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
> >                               gfp_t gfp_mask, nodemask_t *nodemask)
> >  {
> > +     gfp_t current_gfp_mask = current_gfp_context(gfp_mask);
> >       unsigned long nr_reclaimed;
> >       struct scan_control sc = {
> >               .nr_to_reclaim = SWAP_CLUSTER_MAX,
> > -             .gfp_mask = current_gfp_context(gfp_mask),
> > -             .reclaim_idx = gfp_zone(gfp_mask),
> > +             .gfp_mask = current_gfp_mask,
> > +             .reclaim_idx = gfp_zone(current_gfp_mask),
> >               .order = order,
> >               .nodemask = nodemask,
> >               .priority = DEF_PRIORITY,
> > @@ -4158,17 +4159,18 @@ static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned in
> >  {
> >       /* Minimum pages needed in order to stay on node */
> >       const unsigned long nr_pages = 1 << order;
> > +     gfp_t current_gfp_mask = current_gfp_context(gfp_mask);
> >       struct task_struct *p = current;
> >       unsigned int noreclaim_flag;
> >       struct scan_control sc = {
> >               .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
> > -             .gfp_mask = current_gfp_context(gfp_mask),
> > +             .gfp_mask = current_gfp_mask,
> >               .order = order,
> >               .priority = NODE_RECLAIM_PRIORITY,
> >               .may_writepage = !!(node_reclaim_mode & RECLAIM_WRITE),
> >               .may_unmap = !!(node_reclaim_mode & RECLAIM_UNMAP),
> >               .may_swap = 1,
> > -             .reclaim_idx = gfp_zone(gfp_mask),
> > +             .reclaim_idx = gfp_zone(current_gfp_mask),
> >       };
> >
> >       trace_mm_vmscan_node_reclaim_begin(pgdat->node_id, order,
>
> I was hoping we had agreed these are not necessary and they shouldn't be
> touched in the patch.

Thank you for noticing, I was sure I removed these changes, not sure
what happened :(
They will be gone in the next version.

Thank you,
Pasha

> --
> Michal Hocko
> SUSE Labs