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From:   Daniel Jordan <daniel.m.jordan@oracle.com>
To:     Liang Li <liliang.opensource@gmail.com>,
        Alexander Duyck <alexander.h.duyck@linux.intel.com>,
        Mel Gorman <mgorman@techsingularity.net>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Dan Williams <dan.j.williams@intel.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        David Hildenbrand <david@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        Dave Hansen <dave.hansen@intel.com>,
        Michal Hocko <mhocko@suse.com>,
        Liang Li <liliangleo@didiglobal.com>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        virtualization@lists.linux-foundation.org
Subject: Re: [RFC v2 PATCH 0/4] speed up page allocation for __GFP_ZERO
In-Reply-To: <20201221162519.GA22504@open-light-1.localdomain>
References: <20201221162519.GA22504@open-light-1.localdomain>
Date:   Tue, 22 Dec 2020 12:11:21 -0500
Message-ID: <87wnx9rcjq.fsf@oracle.com>
MIME-Version: 1.0
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Liang Li <liliang.opensource@gmail.com> writes:
> The first version can be found at: https://lkml.org/lkml/2020/4/12/42
>
> Zero out the page content usually happens when allocating pages with
> the flag of __GFP_ZERO, this is a time consuming operation, it makes
> the population of a large vma area very slowly. This patch introduce
> a new feature for zero out pages before page allocation, it can help
> to speed up page allocation with __GFP_ZERO.

kzeropaged appears to escape some of the kernel's resource controls, at
least if I'm understanding this right.

The heavy part of a page fault is moved out of the faulting task's
context so the CPU controller can't throttle it.  A task that uses
these pages can benefit from clearing done by CPUs that it's not allowed
to run on.  How can it handle these cases?