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percpu * A couple cleanups by Baoquan He and Bibo Mao. The only behavior change is to start printing messages if we're under the warn limit for failed atomic allocations. percpu_counter * Shakeel introduced percpu counters into mm_struct which caused percpu allocations be on the hot path [1]. Originally I spent some time trying to improve the percpu allocator, but instead preferred what Mateusz Guzik proposed grouping at the allocation site, percpu_counter_init_many(). This allows a single percpu allocation to be shared by the counters. I like this approach because it creates a shared lifetime by the allocations. Additionally, I believe many inits have higher level synchronization requirements, like percpu_counter does against HOTPLUG_CPU. Therefore we can group these optimizations together. [1] https://lore.kernel.org/linux-mm/20221024052841.3291983-1-shakeelb@google.com/ -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEE3hZPHJdcVwe+yTTtiDc0yuoFPR0FAmTv2IUACgkQiDc0yuoF PR0+gg//U430Y9jRSKQtbh3dEPaAeWGcTfSTnVHbQGfBj3A4ePJyWl/Tgzri31AC rzr8SRs0yX8b82TbECWsV67i/GrntLJyz4yQ52S/RRqVwnQqSn/wicEdCY00lJBt Tye8zApOnYBouaYqIOxm/M7ofvKzJ3gWOVeF/zBwM6hwvNaXXtY5r86fSDxoEbhY HOFnCDmg5Spf0U50j1G7nV5KfAb7BNA3/HFyzfzH+w+OWi4IGbThsfrg1qvjyFot KlEK/kF8Af2xj2A2se4XFsLc2D/Tj+29juYVQqIPBJzVPrZ2uerKSszK5Zcr+Use kMiG7tRWKE+2vkOM1RQ5Y5NCVEBhlXlienz1gf/C7247SEGs6OIyqvyDAgPTRx6p oR2/vx9hMtaSMf4aHWd+fYS5gNZ05iMvOIbRZnI1wZkQglQVkJvXhzuLaJ+dIGSP ypv6XOepik7vDjZ3p3xJXd0TAn4NSkn3jWRetrymdtMFanF99qw1VqjmkLecSil0 Gr0UhRL1oiMde6niVJrOpdOGLwt/M4N99Y5rksw6NCnktRJ99coFGj7LglZGMsu+ YkOyjD8MVJXTkBtBNGeqHTKe6nyVkHFq9ad5EmWjPkefP5JziH8i18k7JlF1dLA5 c8peq3ES659D5f0mU2jilD9PsCsBfSn6Of4ruMZa2Zr1XDD8snI= =vcA1 -----END PGP SIGNATURE----- Merge tag 'percpu-for-6.6' of git://git.kernel.org/pub/scm/linux/kernel/git/dennis/percpu Pull percpu updates from Dennis Zhou: "One bigger change to percpu_counter's api allowing for init and destroy of multiple counters via percpu_counter_init_many() and percpu_counter_destroy_many(). This is used to help begin remediating a performance regression with percpu rss stats. Additionally, it seems larger core count machines are feeling the burden of the single threaded allocation of percpu. Mateusz is thinking about it and I will spend some time on it too. percpu: - A couple cleanups by Baoquan He and Bibo Mao. The only behavior change is to start printing messages if we're under the warn limit for failed atomic allocations. percpu_counter: - Shakeel introduced percpu counters into mm_struct which caused percpu allocations be on the hot path [1]. Originally I spent some time trying to improve the percpu allocator, but instead preferred what Mateusz Guzik proposed grouping at the allocation site, percpu_counter_init_many(). This allows a single percpu allocation to be shared by the counters. I like this approach because it creates a shared lifetime by the allocations. Additionally, I believe many inits have higher level synchronization requirements, like percpu_counter does against HOTPLUG_CPU. Therefore we can group these optimizations together" Link: https://lore.kernel.org/linux-mm/20221024052841.3291983-1-shakeelb@google.com/ [1] * tag 'percpu-for-6.6' of git://git.kernel.org/pub/scm/linux/kernel/git/dennis/percpu: kernel/fork: group allocation/free of per-cpu counters for mm struct pcpcntr: add group allocation/free mm/percpu.c: print error message too if atomic alloc failed mm/percpu.c: optimize the code in pcpu_setup_first_chunk() a little bit mm/percpu.c: remove redundant check mm/percpu: Remove some local variables in pcpu_populate_pte |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.