linux-kernel - [PATCH v2 0/4] Optimize mremap during mutual alignment within PMD

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Message-ID: <20230519190934.339332-1-joel@joelfernandes.org>
Date:   Fri, 19 May 2023 19:09:30 +0000
From:   "Joel Fernandes (Google)" <joel@...lfernandes.org>
To:     linux-kernel@...r.kernel.org
Cc:     "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        linux-kselftest@...r.kernel.org, linux-mm@...ck.org,
        Shuah Khan <shuah@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Michal Hocko <mhocko@...e.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Kirill A Shutemov <kirill@...temov.name>,
        "Liam R. Howlett" <liam.howlett@...cle.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Suren Baghdasaryan <surenb@...gle.com>
Subject: [PATCH v2 0/4] Optimize mremap during mutual alignment within PMD

Hello,

Here is v2 of the mremap start address optimization / fix for exec warning.

v1->v2:
1. Trigger the optimization for mremaps smaller than a PMD. I tested by tracing
that it works correctly.

2. Fix issue with bogus return value found by Linus if we broke out of the
above loop for the first PMD itself.

Description of patches:
These patches optimizes the start addresses in move_page_tables() and tests the
changes. It addresses a warning [1] that occurs due to a downward, overlapping
move on a mutually-aligned offset within a PMD during exec. By initiating the
copy process at the PMD level when such alignment is present, we can prevent
this warning and speed up the copying process at the same time. Linus Torvalds
suggested this idea.

Please check the individual patches for more details.

thanks,

 - Joel

[1] https://lore.kernel.org/all/ZB2GTBD%2FLWTrkOiO@dhcp22.suse.cz/

Joel Fernandes (Google) (4):
mm/mremap: Optimize the start addresses in move_page_tables()
selftests: mm: Fix failure case when new remap region was not found
selftests: mm: Add a test for mutually aligned moves > PMD size
selftests: mm: Add a test for remapping to area immediately after
existing mapping

mm/mremap.c                              | 56 +++++++++++++++++++
tools/testing/selftests/mm/mremap_test.c | 69 +++++++++++++++++++++---
2 files changed, 119 insertions(+), 6 deletions(-)

--
2.40.1.698.g37aff9b760-goog