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eb5048ea90
Introduce interfaces __mt_dup() and mtree_dup(), which are used to duplicate a maple tree. They duplicate a maple tree in Depth-First Search (DFS) pre-order traversal. It uses memcopy() to copy nodes in the source tree and allocate new child nodes in non-leaf nodes. The new node is exactly the same as the source node except for all the addresses stored in it. It will be faster than traversing all elements in the source tree and inserting them one by one into the new tree. The time complexity of these two functions is O(n). The difference between __mt_dup() and mtree_dup() is that mtree_dup() handles locks internally. Analysis of the average time complexity of this algorithm: For simplicity, let's assume that the maximum branching factor of all non-leaf nodes is 16 (in allocation mode, it is 10), and the tree is a full tree. Under the given conditions, if there is a maple tree with n elements, the number of its leaves is n/16. From bottom to top, the number of nodes in each level is 1/16 of the number of nodes in the level below. So the total number of nodes in the entire tree is given by the sum of n/16 + n/16^2 + n/16^3 + ... + 1. This is a geometric series, and it has log(n) terms with base 16. According to the formula for the sum of a geometric series, the sum of this series can be calculated as (n-1)/15. Each node has only one parent node pointer, which can be considered as an edge. In total, there are (n-1)/15-1 edges. This algorithm consists of two operations: 1. Traversing all nodes in DFS order. 2. For each node, making a copy and performing necessary modifications to create a new node. For the first part, DFS traversal will visit each edge twice. Let T(ascend) represent the cost of taking one step downwards, and T(descend) represent the cost of taking one step upwards. And both of them are constants (although mas_ascend() may not be, as it contains a loop, but here we ignore it and treat it as a constant). So the time spent on the first part can be represented as ((n-1)/15-1) * (T(ascend) + T(descend)). For the second part, each node will be copied, and the cost of copying a node is denoted as T(copy_node). For each non-leaf node, it is necessary to reallocate all child nodes, and the cost of this operation is denoted as T(dup_alloc). The behavior behind memory allocation is complex and not specific to the maple tree operation. Here, we assume that the time required for a single allocation is constant. Since the size of a node is fixed, both of these symbols are also constants. We can calculate that the time spent on the second part is ((n-1)/15) * T(copy_node) + ((n-1)/15 - n/16) * T(dup_alloc). Adding both parts together, the total time spent by the algorithm can be represented as: ((n-1)/15) * (T(ascend) + T(descend) + T(copy_node) + T(dup_alloc)) - n/16 * T(dup_alloc) - (T(ascend) + T(descend)) Let C1 = T(ascend) + T(descend) + T(copy_node) + T(dup_alloc) Let C2 = T(dup_alloc) Let C3 = T(ascend) + T(descend) Finally, the expression can be simplified as: ((16 * C1 - 15 * C2) / (15 * 16)) * n - (C1 / 15 + C3). This is a linear function, so the average time complexity is O(n). Link: https://lkml.kernel.org/r/20231027033845.90608-4-zhangpeng.00@bytedance.com Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com> Suggested-by: Liam R. Howlett <Liam.Howlett@oracle.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Mateusz Guzik <mjguzik@gmail.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Michael S. Tsirkin <mst@redhat.com> Cc: Mike Christie <michael.christie@oracle.com> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Suren Baghdasaryan <surenb@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> (cherry picked from commit fd32e4e9b7646510ee9010e0d5f8b8857d48a6f7 https://git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm mm-unstable) Bug: 308042511 Change-Id: I385759a1184a202498e086458b572c203616b9b4 Signed-off-by: Suren Baghdasaryan <surenb@google.com>
How do I submit patches to Android Common Kernels
-
BEST: Make all of your changes to upstream Linux. If appropriate, backport to the stable releases. These patches will be merged automatically in the corresponding common kernels. If the patch is already in upstream Linux, post a backport of the patch that conforms to the patch requirements below.
- Do not send patches upstream that contain only symbol exports. To be considered for upstream Linux,
additions of
EXPORT_SYMBOL_GPL()require an in-tree modular driver that uses the symbol -- so include the new driver or changes to an existing driver in the same patchset as the export. - When sending patches upstream, the commit message must contain a clear case for why the patch is needed and beneficial to the community. Enabling out-of-tree drivers or functionality is not not a persuasive case.
- Do not send patches upstream that contain only symbol exports. To be considered for upstream Linux,
additions of
-
LESS GOOD: Develop your patches out-of-tree (from an upstream Linux point-of-view). Unless these are fixing an Android-specific bug, these are very unlikely to be accepted unless they have been coordinated with kernel-team@android.com. If you want to proceed, post a patch that conforms to the patch requirements below.
Common Kernel patch requirements
- All patches must conform to the Linux kernel coding standards and pass
scripts/checkpatch.pl - Patches shall not break gki_defconfig or allmodconfig builds for arm, arm64, x86, x86_64 architectures (see https://source.android.com/setup/build/building-kernels)
- If the patch is not merged from an upstream branch, the subject must be tagged with the type of patch:
UPSTREAM:,BACKPORT:,FROMGIT:,FROMLIST:, orANDROID:. - All patches must have a
Change-Id:tag (see https://gerrit-review.googlesource.com/Documentation/user-changeid.html) - If an Android bug has been assigned, there must be a
Bug:tag. - All patches must have a
Signed-off-by:tag by the author and the submitter
Additional requirements are listed below based on patch type
Requirements for backports from mainline Linux: UPSTREAM:, BACKPORT:
- If the patch is a cherry-pick from Linux mainline with no changes at all
- tag the patch subject with
UPSTREAM:. - add upstream commit information with a
(cherry picked from commit ...)line - Example:
- if the upstream commit message is
- tag the patch subject with
important patch from upstream
This is the detailed description of the important patch
Signed-off-by: Fred Jones <fred.jones@foo.org>
- then Joe Smith would upload the patch for the common kernel as
UPSTREAM: important patch from upstream
This is the detailed description of the important patch
Signed-off-by: Fred Jones <fred.jones@foo.org>
Bug: 135791357
Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
(cherry picked from commit c31e73121f4c1ec41143423ac6ce3ce6dafdcec1)
Signed-off-by: Joe Smith <joe.smith@foo.org>
- If the patch requires any changes from the upstream version, tag the patch with
BACKPORT:instead ofUPSTREAM:.- use the same tags as
UPSTREAM: - add comments about the changes under the
(cherry picked from commit ...)line - Example:
- use the same tags as
BACKPORT: important patch from upstream
This is the detailed description of the important patch
Signed-off-by: Fred Jones <fred.jones@foo.org>
Bug: 135791357
Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
(cherry picked from commit c31e73121f4c1ec41143423ac6ce3ce6dafdcec1)
[joe: Resolved minor conflict in drivers/foo/bar.c ]
Signed-off-by: Joe Smith <joe.smith@foo.org>
Requirements for other backports: FROMGIT:, FROMLIST:,
- If the patch has been merged into an upstream maintainer tree, but has not yet
been merged into Linux mainline
- tag the patch subject with
FROMGIT: - add info on where the patch came from as
(cherry picked from commit <sha1> <repo> <branch>). This must be a stable maintainer branch (not rebased, so don't uselinux-nextfor example). - if changes were required, use
BACKPORT: FROMGIT: - Example:
- if the commit message in the maintainer tree is
- tag the patch subject with
important patch from upstream
This is the detailed description of the important patch
Signed-off-by: Fred Jones <fred.jones@foo.org>
- then Joe Smith would upload the patch for the common kernel as
FROMGIT: important patch from upstream
This is the detailed description of the important patch
Signed-off-by: Fred Jones <fred.jones@foo.org>
Bug: 135791357
(cherry picked from commit 878a2fd9de10b03d11d2f622250285c7e63deace
https://git.kernel.org/pub/scm/linux/kernel/git/foo/bar.git test-branch)
Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
Signed-off-by: Joe Smith <joe.smith@foo.org>
- If the patch has been submitted to LKML, but not accepted into any maintainer tree
- tag the patch subject with
FROMLIST: - add a
Link:tag with a link to the submittal on lore.kernel.org - add a
Bug:tag with the Android bug (required for patches not accepted into a maintainer tree) - if changes were required, use
BACKPORT: FROMLIST: - Example:
- tag the patch subject with
FROMLIST: important patch from upstream
This is the detailed description of the important patch
Signed-off-by: Fred Jones <fred.jones@foo.org>
Bug: 135791357
Link: https://lore.kernel.org/lkml/20190619171517.GA17557@someone.com/
Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
Signed-off-by: Joe Smith <joe.smith@foo.org>
Requirements for Android-specific patches: ANDROID:
- If the patch is fixing a bug to Android-specific code
- tag the patch subject with
ANDROID: - add a
Fixes:tag that cites the patch with the bug - Example:
- tag the patch subject with
ANDROID: fix android-specific bug in foobar.c
This is the detailed description of the important fix
Fixes: 1234abcd2468 ("foobar: add cool feature")
Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
Signed-off-by: Joe Smith <joe.smith@foo.org>
- If the patch is a new feature
- tag the patch subject with
ANDROID: - add a
Bug:tag with the Android bug (required for android-specific features)
- tag the patch subject with