This bug is awaiting verification that the linux-nvidia- tegra-5.15/5.15.0-1023.23~20.04.1 kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-focal-linux- nvidia-tegra-5.15' to 'verification-done-focal-linux-nvidia-tegra-5.15'. If the problem still exists, change the tag 'verification-needed-focal- linux-nvidia-tegra-5.15' to 'verification-failed-focal-linux-nvidia- tegra-5.15'.
If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you! ** Tags added: kernel-spammed-focal-linux-nvidia-tegra-5.15-v2 verification-needed-focal-linux-nvidia-tegra-5.15 -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/2053152 Title: performance: mm/percpu-internal.h: Re-layout pcpu_chunk to mitigate false sharing Status in linux package in Ubuntu: Fix Released Status in linux source package in Jammy: Fix Committed Bug description: This is a public version of https://bugs.launchpad.net/bugs/2034984 [Description] When running UnixBench/Execl throughput case, false sharing is observed due to frequent read on base_addr and write on free_bytes, chunk_md. UnixBench/Execl represents a class of workload where bash scripts are spawned frequently to do some short jobs. It will do system call on execl frequently, and execl will call mm_init to initialize mm_struct of the process. mm_init will call __percpu_counter_init for percpu_counters initialization. Then pcpu_alloc is called to read the base_addr of pcpu_chunk for memory allocation. Inside pcpu_alloc, it will call pcpu_alloc_area to allocate memory from a specified chunk. This function will update "free_bytes" and "chunk_md" to record the rest free bytes and other meta data for this chunk. Correspondingly, pcpu_free_area will also update these 2 members when free memory. In current pcpu_chunk layout, `base_addr' is in the same cache line with `free_bytes' and `chunk_md', and `base_addr' is at the last 8 bytes. This patch moves `bound_map' up to `base_addr', to let `base_addr' locate in a new cacheline. [Hardware Information] Architecture: Intel / AMD (x86_64) Platform(s): Platform-Independent Date HW is expected at Canonical: Component(s): Performance and Scalability [Software Information] Target Version: 23.10 Target Kernel: 6.5 Commit IDs: 3a6358c0dbe6 percpu-internal/pcpu_chunk: re-layout pcpu_chunk structure to reduce false sharing External Links: [Business Justification] [Testing guidance] [External ID] OSVE-5160 The following requested patch has been applied upstream for v6.5-rc1: - 3a6358c0dbe6 percpu-internal/pcpu_chunk: re-layout pcpu_chunk structure to reduce false sharing https://github.com/torvalds/linux/commit/3a6358c0dbe6a286a4f4504ba392a6039a9fbd12 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2053152/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
