| Message ID | 20231016032226.59199-1-zhangpeng.00@bytedance.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | Introduce __mt_dup() to improve the performance of fork() | expand |
在 2023/10/16 11:22, Peng Zhang 写道: > Hi all, > > This series introduces __mt_dup() to improve the performance of fork(). During > the duplication process of mmap, all VMAs are traversed and inserted one by one > into the new maple tree, causing the maple tree to be rebalanced multiple times. > Balancing the maple tree is a costly operation. To duplicate VMAs more > efficiently, mtree_dup() and __mt_dup() are introduced for the maple tree. They > can efficiently duplicate a maple tree. > > Here are some algorithmic details about {mtree,__mt}_dup(). We perform a DFS > pre-order traversal of all nodes in the source maple tree. During this process, > we fully copy the nodes from the source tree to the new tree. This involves > memory allocation, and when encountering a new node, if it is a non-leaf node, > all its child nodes are allocated at once. > > Some previous discussions can be referred to as [1]. For a more detailed > analysis of the algorithm, please refer to the logs for patch [3/10] and patch > [10/10] > > There is a "spawn" in byte-unixbench[2], which can be used to test the > performance of fork(). I modified it slightly to make it work with > different number of VMAs. > > Below are the test results. The first row shows the number of VMAs. > The second and third rows show the number of fork() calls per ten seconds, > corresponding to next-20231006 and the this patchset, respectively. The > test results were obtained with CPU binding to avoid scheduler load > balancing that could cause unstable results. There are still some > fluctuations in the test results, but at least they are better than the > original performance. > > 21 121 221 421 821 1621 3221 6421 12821 25621 51221 > 112100 76261 54227 34035 20195 11112 6017 3161 1606 802 393 > 114558 83067 65008 45824 28751 16072 8922 4747 2436 1233 599 > 2.19% 8.92% 19.88% 34.64% 42.37% 44.64% 48.28% 50.17% 51.68% 53.74% 52.42% > > Thanks for Liam's review. > > Changes since v4: > - Change the handling method for the failure of dup_mmap(). Handle it in > exit_mmap(). > - Update check_forking() and bench_forking(). > - Add the corresponding copyright statement. > I apologize for forgetting to include all the links while editing the cover letter. Here they are: [1] https://lore.kernel.org/lkml/463899aa-6cbd-f08e-0aca-077b0e4e4475@bytedance.com/ [2] https://github.com/kdlucas/byte-unixbench/tree/master v1: https://lore.kernel.org/lkml/20230726080916.17454-1-zhangpeng.00@bytedance.com/ v2: https://lore.kernel.org/lkml/20230830125654.21257-1-zhangpeng.00@bytedance.com/ v3: https://lore.kernel.org/lkml/20230925035617.84767-1-zhangpeng.00@bytedance.com/ v4: https://lore.kernel.org/lkml/20231009090320.64565-1-zhangpeng.00@bytedance.com/ > Peng Zhang (10): > maple_tree: Add mt_free_one() and mt_attr() helpers > maple_tree: Introduce {mtree,mas}_lock_nested() > maple_tree: Introduce interfaces __mt_dup() and mtree_dup() > radix tree test suite: Align kmem_cache_alloc_bulk() with kernel > behavior. > maple_tree: Add test for mtree_dup() > maple_tree: Update the documentation of maple tree > maple_tree: Skip other tests when BENCH is enabled > maple_tree: Update check_forking() and bench_forking() > maple_tree: Preserve the tree attributes when destroying maple tree > fork: Use __mt_dup() to duplicate maple tree in dup_mmap() > > Documentation/core-api/maple_tree.rst | 4 + > include/linux/maple_tree.h | 7 + > kernel/fork.c | 39 ++- > lib/maple_tree.c | 304 ++++++++++++++++++++- > lib/test_maple_tree.c | 123 +++++---- > mm/memory.c | 7 +- > mm/mmap.c | 9 +- > tools/include/linux/rwsem.h | 4 + > tools/include/linux/spinlock.h | 1 + > tools/testing/radix-tree/linux.c | 45 +++- > tools/testing/radix-tree/maple.c | 363 ++++++++++++++++++++++++++ > 11 files changed, 815 insertions(+), 91 deletions(-) >
Hi all, This series introduces __mt_dup() to improve the performance of fork(). During the duplication process of mmap, all VMAs are traversed and inserted one by one into the new maple tree, causing the maple tree to be rebalanced multiple times. Balancing the maple tree is a costly operation. To duplicate VMAs more efficiently, mtree_dup() and __mt_dup() are introduced for the maple tree. They can efficiently duplicate a maple tree. Here are some algorithmic details about {mtree,__mt}_dup(). We perform a DFS pre-order traversal of all nodes in the source maple tree. During this process, we fully copy the nodes from the source tree to the new tree. This involves memory allocation, and when encountering a new node, if it is a non-leaf node, all its child nodes are allocated at once. Some previous discussions can be referred to as [1]. For a more detailed analysis of the algorithm, please refer to the logs for patch [3/10] and patch [10/10] There is a "spawn" in byte-unixbench[2], which can be used to test the performance of fork(). I modified it slightly to make it work with different number of VMAs. Below are the test results. The first row shows the number of VMAs. The second and third rows show the number of fork() calls per ten seconds, corresponding to next-20231006 and the this patchset, respectively. The test results were obtained with CPU binding to avoid scheduler load balancing that could cause unstable results. There are still some fluctuations in the test results, but at least they are better than the original performance. 21 121 221 421 821 1621 3221 6421 12821 25621 51221 112100 76261 54227 34035 20195 11112 6017 3161 1606 802 393 114558 83067 65008 45824 28751 16072 8922 4747 2436 1233 599 2.19% 8.92% 19.88% 34.64% 42.37% 44.64% 48.28% 50.17% 51.68% 53.74% 52.42% Thanks for Liam's review. Changes since v4: - Change the handling method for the failure of dup_mmap(). Handle it in exit_mmap(). - Update check_forking() and bench_forking(). - Add the corresponding copyright statement. Peng Zhang (10): maple_tree: Add mt_free_one() and mt_attr() helpers maple_tree: Introduce {mtree,mas}_lock_nested() maple_tree: Introduce interfaces __mt_dup() and mtree_dup() radix tree test suite: Align kmem_cache_alloc_bulk() with kernel behavior. maple_tree: Add test for mtree_dup() maple_tree: Update the documentation of maple tree maple_tree: Skip other tests when BENCH is enabled maple_tree: Update check_forking() and bench_forking() maple_tree: Preserve the tree attributes when destroying maple tree fork: Use __mt_dup() to duplicate maple tree in dup_mmap() Documentation/core-api/maple_tree.rst | 4 + include/linux/maple_tree.h | 7 + kernel/fork.c | 39 ++- lib/maple_tree.c | 304 ++++++++++++++++++++- lib/test_maple_tree.c | 123 +++++---- mm/memory.c | 7 +- mm/mmap.c | 9 +- tools/include/linux/rwsem.h | 4 + tools/include/linux/spinlock.h | 1 + tools/testing/radix-tree/linux.c | 45 +++- tools/testing/radix-tree/maple.c | 363 ++++++++++++++++++++++++++ 11 files changed, 815 insertions(+), 91 deletions(-)