linux-kernel - Re: [PATCH v2] mm/uffd: UFFD_FEATURE_WP

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Message-ID: <982c1623-ac28-2743-d6a3-4faf42f72d47@redhat.com>
Date:   Thu, 2 Mar 2023 15:01:26 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Peter Xu <peterx@...hat.com>
Cc:     Muhammad Usama Anjum <usama.anjum@...labora.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        "kernel@...labora.com" <kernel@...labora.com>
Subject: Re: [PATCH v2] mm/uffd: UFFD_FEATURE_WP_UNPOPULATED

On 02.03.23 14:57, Peter Xu wrote:
> On Thu, Mar 02, 2023 at 10:37:44AM +0100, David Hildenbrand wrote:
>> Especially for such large sparse VMAs, the current way of allocating
>> pagetables to place markers/zeropages is far from optimal.
> 
> IMHO that's not a generic workload.  As mentioned in the reply there, I
> would suggest we go with simple then we have space to optimize it in the
> future if necessary, because the API will be the same.
> 

I disagree with "generic workload", we use sparse mmaps all over the 
place, and when blindly used by e.g., CRIU, we'll simply end up wasting 
memory and time.

But I already agreed that this optimization that is a separate thing to 
implement.

-- 
Thanks,

David / dhildenb