From:   Nadav Amit <namit@vmware.com>
To:     Peter Xu <peterx@redhat.com>
CC:     Muhammad Usama Anjum <usama.anjum@collabora.com>,
        Mike Rapoport <rppt@kernel.org>,
        =?iso-8859-2?Q?Micha=B3_Miros=B3aw?= <emmir@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Cyrill Gorcunov <gorcunov@gmail.com>,
        Paul Gofman <pgofman@codeweavers.com>,
        Danylo Mocherniuk <mdanylo@google.com>,
        Shuah Khan <shuah@kernel.org>,
        Christian Brauner <brauner@kernel.org>,
        Yang Shi <shy828301@gmail.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        "Liam R . Howlett" <Liam.Howlett@oracle.com>,
        Yun Zhou <yun.zhou@windriver.com>,
        Suren Baghdasaryan <surenb@google.com>,
        Alex Sierra <alex.sierra@amd.com>,
        Matthew Wilcox <willy@infradead.org>,
        Pasha Tatashin <pasha.tatashin@soleen.com>,
        Axel Rasmussen <axelrasmussen@google.com>,
        "Gustavo A . R . Silva" <gustavoars@kernel.org>,
        Dan Williams <dan.j.williams@intel.com>,
        kernel list <linux-kernel@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>,
        linux-kselftest <linux-kselftest@vger.kernel.org>,
        Greg KH <gregkh@linuxfoundation.org>,
        "kernel@collabora.com" <kernel@collabora.com>,
        David Hildenbrand <david@redhat.com>,
        Andrei Vagin <avagin@gmail.com>
Subject: Re: [PATCH v10 3/6] fs/proc/task_mmu: Implement IOCTL to get and/or
 the clear info about PTEs
Thread-Topic: [PATCH v10 3/6] fs/proc/task_mmu: Implement IOCTL to get and/or
 the clear info about PTEs
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Date:   Wed, 1 Mar 2023 01:59:47 +0000
Message-ID: <99887AA3-8023-4462-A870-995A47383175@vmware.com>
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> On Feb 28, 2023, at 11:31 AM, Peter Xu <peterx@redhat.com> wrote:
>=20
>> Anyhow, thanks for all the explanations. Eventually, I understand that
>> using bitmaps can be more efficient than a log if the bits are condensed=
.
>=20
> Note that I think what Muhammad (sorry, Muhammad! I think I spelled your
> name wrongly before starting from some email..) proposed is not a bitmap,
> but an array of ranges that can coalesce the result into very condensed
> form.  Pros and cons.
>=20
> Again, I can't comment much on that API, but since there're a bunch of
> other developers looking at that and they're also potential future users,
> I'll trust their judgement and just focus more on the other side of thing=
s.


Thanks Peter for your patience.

I would just note that I understood that Muhammad did not propose a condens=
ed
bitmap, and that was a hint that handling a condensed bitmap (at least on x=
86)
can be done rather efficiently. I am not sure about other representations.

Thanks for your explanations again, Peter.=