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From:   Pavel Tatashin <pasha.tatashin@soleen.com>
Date:   Fri, 4 Dec 2020 11:07:51 -0500
Message-ID: <CA+CK2bCyMWMXpz9xmPMRey0euS1AYuPEjmXo6OF9Hsv9x+f9GQ@mail.gmail.com>
Subject: Re: [PATCH 5/6] mm: honor PF_MEMALLOC_NOMOVABLE for all allocations
To:     Michal Hocko <mhocko@suse.com>
Cc:     LKML <linux-kernel@vger.kernel.org>, linux-mm <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        David Hildenbrand <david@redhat.com>,
        Oscar Salvador <osalvador@suse.de>,
        Dan Williams <dan.j.williams@intel.com>,
        Sasha Levin <sashal@kernel.org>,
        Tyler Hicks <tyhicks@linux.microsoft.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>, mike.kravetz@oracle.com,
        Steven Rostedt <rostedt@goodmis.org>,
        Ingo Molnar <mingo@redhat.com>, Jason Gunthorpe <jgg@ziepe.ca>,
        Peter Zijlstra <peterz@infradead.org>,
        Mel Gorman <mgorman@suse.de>,
        Matthew Wilcox <willy@infradead.org>,
        David Rientjes <rientjes@google.com>,
        John Hubbard <jhubbard@nvidia.com>
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On Fri, Dec 4, 2020 at 3:54 AM Michal Hocko <mhocko@suse.com> wrote:
>
> On Fri 04-12-20 09:43:13, Michal Hocko wrote:
> > On Thu 03-12-20 10:15:41, Pavel Tatashin wrote:
> [...]
> > > Also, current_gfp_context() is used elsewhere, and in some
> > > places removing __GFP_MOVABLE from gfp_mask means that we will need to
> > > also change other things. For example [1], in try_to_free_pages() we
> > > call current_gfp_context(gfp_mask) which can reduce the maximum zone
> > > idx, yet we simply set it to: reclaim_idx = gfp_zone(gfp_mask), not to
> > > the newly determined gfp_mask.
> >
> > Yes and the direct reclaim should honor the movable zone restriction.
> > Why should we reclaim ZONE_MOVABLE when the allocation cannot really
> > allocate from it? Or have I misunderstood your concern?
>
> Btw. if we have gfp mask properly filtered for the fast path then we can
> remove the additional call to current_gfp_context from the direct
> reclaim path. Something for a separate patch.

Good point. I am thinking to make a preparation patch at the beginning
of the series where we move current_gfp_context() to the fast path,
and also address all other cases where this call is not going to be
needed anymore, or where the gfp_mask will needed to be set according
to what current_gfp_context() returned.

Thanks,
Pasha