From: Richard Weinberger <richard@nod.at>
To: David Hildenbrand <david@redhat.com>
Cc: linux-mm <linux-mm@kvack.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Linux Doc Mailing List <linux-doc@vger.kernel.org>,
upstream+pagemap@sigma-star.at, adobriyan@gmail.com,
wangkefeng wang <wangkefeng.wang@huawei.com>,
ryan roberts <ryan.roberts@arm.com>,
hughd@google.com, peterx@redhat.com, avagin@google.com,
lstoakes@gmail.com, vbabka <vbabka@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
usama anjum <usama.anjum@collabora.com>,
Jonathan Corbet <corbet@lwn.net>
Subject: Re: [PATCH 1/2] [RFC] proc: pagemap: Expose whether a PTE is writable
Date: Thu, 7 Mar 2024 12:10:43 +0100 (CET) [thread overview]
Message-ID: <1058679077.23275.1709809843605.JavaMail.zimbra@nod.at> (raw)
In-Reply-To: <d673247b-a67b-43e1-a947-18fdae5f0ea1@redhat.com>
----- Ursprüngliche Mail -----
> Von: "David Hildenbrand" <david@redhat.com>
> But why is that required? What is the target use case? (I did not get
> the cover letter in my inbox)
>
> We're running slowly but steadily out of bits, so we better make wise
> decisions.
>
> Also, consider: Architectures where the dirty/access bit is not HW
> managed could indicate "writable" here although we *will* get a page
> fault to set the page dirty/accessed.
I'm currently investigating why a real-time application faces unexpected
page faults. Page faults are usually fatal for real-time work loads because
the latency constraints are no longer met.
So, I wrote a small tool to inspect the memory mappings of a process to find
areas which are not correctly pre-faulted. While doing so I noticed that
there is currently no way to detect CoW mappings.
Exposing the writable property of a PTE seemed like a good start to me.
> So best this can universally do is say "this PTE currently has write
> permissions".
Ok.
Thanks,
//richard
next prev parent reply other threads:[~2024-03-07 11:10 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-06 23:23 [PATCH 1/2] [RFC] proc: pagemap: Expose whether a PTE is writable Richard Weinberger
2024-03-06 23:23 ` [PATCH 2/2] [RFC] pagemap.rst: Document write bit Richard Weinberger
2024-03-07 10:52 ` David Hildenbrand
2024-03-07 11:10 ` Richard Weinberger
2024-03-07 11:15 ` David Hildenbrand
2024-03-10 22:14 ` Lorenzo Stoakes
2024-03-07 10:44 ` [PATCH 1/2] [RFC] proc: pagemap: Expose whether a PTE is writable Muhammad Usama Anjum
2024-03-07 10:52 ` David Hildenbrand
2024-03-07 11:10 ` Richard Weinberger [this message]
2024-03-07 11:20 ` David Hildenbrand
2024-03-07 11:51 ` Richard Weinberger
2024-03-07 11:59 ` David Hildenbrand
2024-03-07 12:09 ` David Hildenbrand
2024-03-07 14:42 ` Richard Weinberger
2024-03-10 21:55 ` Lorenzo Stoakes
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1058679077.23275.1709809843605.JavaMail.zimbra@nod.at \
--to=richard@nod.at \
--cc=adobriyan@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=avagin@google.com \
--cc=corbet@lwn.net \
--cc=david@redhat.com \
--cc=hughd@google.com \
--cc=linux-doc@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=lstoakes@gmail.com \
--cc=peterx@redhat.com \
--cc=ryan.roberts@arm.com \
--cc=upstream+pagemap@sigma-star.at \
--cc=usama.anjum@collabora.com \
--cc=vbabka@suse.cz \
--cc=wangkefeng.wang@huawei.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).