diff options
| -rw-r--r-- | include/linux/padata.h | 29 | ||||
| -rw-r--r-- | kernel/padata.c | 152 |
2 files changed, 178 insertions, 3 deletions
diff --git a/include/linux/padata.h b/include/linux/padata.h index b4da88f8588c..7302efff5e65 100644 --- a/include/linux/padata.h +++ b/include/linux/padata.h @@ -4,6 +4,9 @@ * * Copyright (C) 2008, 2009 secunet Security Networks AG * Copyright (C) 2008, 2009 Steffen Klassert <steffen.klassert@secunet.com> + * + * Copyright (c) 2020 Oracle and/or its affiliates. + * Author: Daniel Jordan <daniel.m.jordan@oracle.com> */ #ifndef PADATA_H @@ -131,6 +134,31 @@ struct padata_shell { }; /** + * struct padata_mt_job - represents one multithreaded job + * + * @thread_fn: Called for each chunk of work that a padata thread does. + * @fn_arg: The thread function argument. + * @start: The start of the job (units are job-specific). + * @size: size of this node's work (units are job-specific). + * @align: Ranges passed to the thread function fall on this boundary, with the + * possible exceptions of the beginning and end of the job. + * @min_chunk: The minimum chunk size in job-specific units. This allows + * the client to communicate the minimum amount of work that's + * appropriate for one worker thread to do at once. + * @max_threads: Max threads to use for the job, actual number may be less + * depending on task size and minimum chunk size. + */ +struct padata_mt_job { + void (*thread_fn)(unsigned long start, unsigned long end, void *arg); + void *fn_arg; + unsigned long start; + unsigned long size; + unsigned long align; + unsigned long min_chunk; + int max_threads; +}; + +/** * struct padata_instance - The overall control structure. * * @cpu_online_node: Linkage for CPU online callback. @@ -173,6 +201,7 @@ extern void padata_free_shell(struct padata_shell *ps); extern int padata_do_parallel(struct padata_shell *ps, struct padata_priv *padata, int *cb_cpu); extern void padata_do_serial(struct padata_priv *padata); +extern void __init padata_do_multithreaded(struct padata_mt_job *job); extern int padata_set_cpumask(struct padata_instance *pinst, int cpumask_type, cpumask_var_t cpumask); extern int padata_start(struct padata_instance *pinst); diff --git a/kernel/padata.c b/kernel/padata.c index d779a73d4d92..29fc5d87a4cd 100644 --- a/kernel/padata.c +++ b/kernel/padata.c @@ -7,6 +7,9 @@ * Copyright (C) 2008, 2009 secunet Security Networks AG * Copyright (C) 2008, 2009 Steffen Klassert <steffen.klassert@secunet.com> * + * Copyright (c) 2020 Oracle and/or its affiliates. + * Author: Daniel Jordan <daniel.m.jordan@oracle.com> + * * This program is free software; you can redistribute it and/or modify it * under the terms and conditions of the GNU General Public License, * version 2, as published by the Free Software Foundation. @@ -21,6 +24,7 @@ * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA. */ +#include <linux/completion.h> #include <linux/export.h> #include <linux/cpumask.h> #include <linux/err.h> @@ -32,6 +36,8 @@ #include <linux/sysfs.h> #include <linux/rcupdate.h> +#define PADATA_WORK_ONSTACK 1 /* Work's memory is on stack */ + struct padata_work { struct work_struct pw_work; struct list_head pw_list; /* padata_free_works linkage */ @@ -42,7 +48,17 @@ static DEFINE_SPINLOCK(padata_works_lock); static struct padata_work *padata_works; static LIST_HEAD(padata_free_works); +struct padata_mt_job_state { + spinlock_t lock; + struct completion completion; + struct padata_mt_job *job; + int nworks; + int nworks_fini; + unsigned long chunk_size; +}; + static void padata_free_pd(struct parallel_data *pd); +static void __init padata_mt_helper(struct work_struct *work); static int padata_index_to_cpu(struct parallel_data *pd, int cpu_index) { @@ -81,18 +97,56 @@ static struct padata_work *padata_work_alloc(void) } static void padata_work_init(struct padata_work *pw, work_func_t work_fn, - void *data) + void *data, int flags) { - INIT_WORK(&pw->pw_work, work_fn); + if (flags & PADATA_WORK_ONSTACK) + INIT_WORK_ONSTACK(&pw->pw_work, work_fn); + else + INIT_WORK(&pw->pw_work, work_fn); pw->pw_data = data; } +static int __init padata_work_alloc_mt(int nworks, void *data, + struct list_head *head) +{ + int i; + + spin_lock(&padata_works_lock); + /* Start at 1 because the current task participates in the job. */ + for (i = 1; i < nworks; ++i) { + struct padata_work *pw = padata_work_alloc(); + + if (!pw) + break; + padata_work_init(pw, padata_mt_helper, data, 0); + list_add(&pw->pw_list, head); + } + spin_unlock(&padata_works_lock); + + return i; +} + static void padata_work_free(struct padata_work *pw) { lockdep_assert_held(&padata_works_lock); list_add(&pw->pw_list, &padata_free_works); } +static void __init padata_works_free(struct list_head *works) +{ + struct padata_work *cur, *next; + + if (list_empty(works)) + return; + + spin_lock(&padata_works_lock); + list_for_each_entry_safe(cur, next, works, pw_list) { + list_del(&cur->pw_list); + padata_work_free(cur); + } + spin_unlock(&padata_works_lock); +} + static void padata_parallel_worker(struct work_struct *parallel_work) { struct padata_work *pw = container_of(parallel_work, struct padata_work, @@ -168,7 +222,7 @@ int padata_do_parallel(struct padata_shell *ps, pw = padata_work_alloc(); spin_unlock(&padata_works_lock); if (pw) { - padata_work_init(pw, padata_parallel_worker, padata); + padata_work_init(pw, padata_parallel_worker, padata, 0); queue_work(pinst->parallel_wq, &pw->pw_work); } else { /* Maximum works limit exceeded, run in the current task. */ @@ -409,6 +463,98 @@ out: return err; } +static void __init padata_mt_helper(struct work_struct *w) +{ + struct padata_work *pw = container_of(w, struct padata_work, pw_work); + struct padata_mt_job_state *ps = pw->pw_data; + struct padata_mt_job *job = ps->job; + bool done; + + spin_lock(&ps->lock); + + while (job->size > 0) { + unsigned long start, size, end; + + start = job->start; + /* So end is chunk size aligned if enough work remains. */ + size = roundup(start + 1, ps->chunk_size) - start; + size = min(size, job->size); + end = start + size; + + job->start = end; + job->size -= size; + + spin_unlock(&ps->lock); + job->thread_fn(start, end, job->fn_arg); + spin_lock(&ps->lock); + } + + ++ps->nworks_fini; + done = (ps->nworks_fini == ps->nworks); + spin_unlock(&ps->lock); + + if (done) + complete(&ps->completion); +} + +/** + * padata_do_multithreaded - run a multithreaded job + * @job: Description of the job. + * + * See the definition of struct padata_mt_job for more details. + */ +void __init padata_do_multithreaded(struct padata_mt_job *job) +{ + /* In case threads finish at different times. */ + static const unsigned long load_balance_factor = 4; + struct padata_work my_work, *pw; + struct padata_mt_job_state ps; + LIST_HEAD(works); + int nworks; + + if (job->size == 0) + return; + + /* Ensure at least one thread when size < min_chunk. */ + nworks = max(job->size / job->min_chunk, 1ul); + nworks = min(nworks, job->max_threads); + + if (nworks == 1) { + /* Single thread, no coordination needed, cut to the chase. */ + job->thread_fn(job->start, job->start + job->size, job->fn_arg); + return; + } + + spin_lock_init(&ps.lock); + init_completion(&ps.completion); + ps.job = job; + ps.nworks = padata_work_alloc_mt(nworks, &ps, &works); + ps.nworks_fini = 0; + + /* + * Chunk size is the amount of work a helper does per call to the + * thread function. Load balance large jobs between threads by + * increasing the number of chunks, guarantee at least the minimum + * chunk size from the caller, and honor the caller's alignment. + */ + ps.chunk_size = job->size / (ps.nworks * load_balance_factor); + ps.chunk_size = max(ps.chunk_size, job->min_chunk); + ps.chunk_size = roundup(ps.chunk_size, job->align); + + list_for_each_entry(pw, &works, pw_list) + queue_work(system_unbound_wq, &pw->pw_work); + + /* Use the current thread, which saves starting a workqueue worker. */ + padata_work_init(&my_work, padata_mt_helper, &ps, PADATA_WORK_ONSTACK); + padata_mt_helper(&my_work.pw_work); + + /* Wait for all the helpers to finish. */ + wait_for_completion(&ps.completion); + + destroy_work_on_stack(&my_work.pw_work); + padata_works_free(&works); +} + static void __padata_list_init(struct padata_list *pd_list) { INIT_LIST_HEAD(&pd_list->list); |