On Tue, 5 Dec 2017 14:52:15 -0500 Daniel Jordan <[email protected]>
wrote:
> ktask is a generic framework for parallelizing CPU-intensive work in the
> kernel. The intended use is for big machines that can use their CPU power to
> speed up large tasks that can't otherwise be multithreaded in userland. The
> API is generic enough to add concurrency to many different kinds of tasks--for
> example, zeroing a range of pages or evicting a list of inodes--and aims to
> save its clients the trouble of splitting up the work, choosing the number of
> threads to use, maintaining an efficient concurrency level, starting these
> threads, and load balancing the work between them.
>
> The Documentation patch earlier in this series has more background.
>
> Introduces the ktask API; consumers appear in subsequent patches.
>
> Based on work by Pavel Tatashin, Steve Sistare, and Jonathan Adams.
>
> ...
>
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -319,6 +319,18 @@ config AUDIT_TREE
> depends on AUDITSYSCALL
> select FSNOTIFY
>
> +config KTASK
> + bool "Multithread cpu-intensive kernel tasks"
> + depends on SMP
> + depends on NR_CPUS > 16
Why this?
It would make sense to relax (or eliminate) this at least for the
development/test period, so more people actually run and test the new
code.
> + default n
> + help
> + Parallelize expensive kernel tasks such as zeroing huge pages. This
> + feature is designed for big machines that can take advantage of
> their
> + cpu count to speed up large kernel tasks.
> +
> + If unsure, say 'N'.
> +
> source "kernel/irq/Kconfig"
> source "kernel/time/Kconfig"
>
>
> ...
>
> +/*
> + * Initialize internal limits on work items queued. Work items submitted to
> + * cmwq capped at 80% of online cpus both system-wide and per-node to
> maintain
> + * an efficient level of parallelization at these respective levels.
> + */
> +bool ktask_rlim_init(void)
Why not static __init?
> +{
> + int node;
> + unsigned nr_node_cpus;
> +
> + spin_lock_init(&ktask_rlim_lock);
This can be done at compile time. Unless there's a real reason for
ktask_rlim_init to be non-static, non-__init, in which case I'm
worried: reinitializing a static spinlock is weird.
> + ktask_rlim_node_cur = kcalloc(num_possible_nodes(),
> + sizeof(size_t),
> + GFP_KERNEL);
> + if (!ktask_rlim_node_cur) {
> + pr_warn("can't alloc rlim counts (ktask disabled)");
> + return false;
> + }
> +
> + ktask_rlim_node_max = kmalloc_array(num_possible_nodes(),
> + sizeof(size_t),
> + GFP_KERNEL);
> + if (!ktask_rlim_node_max) {
> + kfree(ktask_rlim_node_cur);
> + pr_warn("can't alloc rlim maximums (ktask disabled)");
> + return false;
> + }
> +
> + ktask_rlim_max = mult_frac(num_online_cpus(), KTASK_CPUFRAC_NUMER,
> + KTASK_CPUFRAC_DENOM);
> + for_each_node(node) {
> + nr_node_cpus = cpumask_weight(cpumask_of_node(node));
> + ktask_rlim_node_max[node] = mult_frac(nr_node_cpus,
> + KTASK_CPUFRAC_NUMER,
> + KTASK_CPUFRAC_DENOM);
> + }
> +
> + return true;
> +}
>
> ...
>
