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Date: Thu, 24 Jan 2013 18:29:36 +0900 From: Joonsoo Kim <iamjoonsoo.kim@....com> To: Tejun Heo <tj@...nel.org> Cc: linux-kernel@...r.kernel.org, Lai Jiangshan <laijs@...fujitsu.com> Subject: Re: [PATCH v2 15/17] workqueue: remove global_cwq Hello, Tejun. On Wed, Jan 23, 2013 at 10:09:57AM -0800, Tejun Heo wrote: > global_cwq is now nothing but a container for per-cpu standard > worker_pools. Declare the worker pools directly as > cpu/unbound_std_worker_pools[] and remove global_cwq. > > * ____cacheline_aligned_in_smp moved from global_cwq to worker_pool. > This probably would have made sense even before this change as we > want each pool to be aligned. > > * get_gcwq() is replaced with std_worker_pools() which returns the > pointer to the standard pool array for a given CPU. > > * __alloc_workqueue_key() updated to use get_std_worker_pool() instead > of open-coding pool determination. > > This is part of an effort to remove global_cwq and make worker_pool > the top level abstraction, which in turn will help implementing worker > pools with user-specified attributes. > > v2: Joonsoo pointed out that it'd better to align struct worker_pool > rather than the array so that every pool is aligned. > > Signed-off-by: Tejun Heo <tj@...nel.org> > Cc: Joonsoo Kim <js1304@...il.com> > --- > Rebased on top of the current wq/for-3.9 and Joonsoo's comments > applied. > > Thanks. > > kernel/workqueue.c | 46 ++++++++++++++++---------------------------- > kernel/workqueue_internal.h | 1 > 2 files changed, 17 insertions(+), 30 deletions(-) > > --- a/kernel/workqueue.c > +++ b/kernel/workqueue.c > @@ -144,16 +144,6 @@ struct worker_pool { > > struct mutex assoc_mutex; /* protect POOL_DISASSOCIATED */ > struct ida worker_ida; /* L: for worker IDs */ > -}; > - > -/* > - * Global per-cpu workqueue. There's one and only one for each cpu > - * and all works are queued and processed here regardless of their > - * target workqueues. > - */ > -struct global_cwq { > - struct worker_pool pools[NR_STD_WORKER_POOLS]; > - /* normal and highpri pools */ > } ____cacheline_aligned_in_smp; > > /* > @@ -250,8 +240,8 @@ EXPORT_SYMBOL_GPL(system_freezable_wq); > #include <trace/events/workqueue.h> > > #define for_each_std_worker_pool(pool, cpu) \ > - for ((pool) = &get_gcwq((cpu))->pools[0]; \ > - (pool) < &get_gcwq((cpu))->pools[NR_STD_WORKER_POOLS]; (pool)++) > + for ((pool) = &std_worker_pools(cpu)[0]; \ > + (pool) < &std_worker_pools(cpu)[NR_STD_WORKER_POOLS]; (pool)++) > > #define for_each_busy_worker(worker, i, pos, pool) \ > hash_for_each(pool->busy_hash, i, pos, worker, hentry) > @@ -427,19 +417,19 @@ static LIST_HEAD(workqueues); > static bool workqueue_freezing; /* W: have wqs started freezing? */ > > /* > - * The almighty global cpu workqueues. nr_running is the only field > - * which is expected to be used frequently by other cpus via > - * try_to_wake_up(). Put it in a separate cacheline. > + * The CPU standard worker pools. nr_running is the only field which is > + * expected to be used frequently by other cpus via try_to_wake_up(). Put > + * it in a separate cacheline. > */ > -static DEFINE_PER_CPU(struct global_cwq, global_cwq); > +static DEFINE_PER_CPU(struct worker_pool [NR_STD_WORKER_POOLS], > + cpu_std_worker_pools); > static DEFINE_PER_CPU_SHARED_ALIGNED(atomic_t, pool_nr_running[NR_STD_WORKER_POOLS]); AFAIK, worker_pool can be accessed by other cpus. So, I think that we also need "DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [], xxx)". > /* > - * Global cpu workqueue and nr_running counter for unbound gcwq. The pools > - * for online CPUs have POOL_DISASSOCIATED set, and all their workers have > - * WORKER_UNBOUND set. > + * Standard worker pools and nr_running counter for unbound CPU. The pools > + * have POOL_DISASSOCIATED set, and all workers have WORKER_UNBOUND set. > */ > -static struct global_cwq unbound_global_cwq; > +static struct worker_pool unbound_std_worker_pools[NR_STD_WORKER_POOLS]; > static atomic_t unbound_pool_nr_running[NR_STD_WORKER_POOLS] = { > [0 ... NR_STD_WORKER_POOLS - 1] = ATOMIC_INIT(0), /* always 0 */ > }; > @@ -450,17 +440,17 @@ static DEFINE_IDR(worker_pool_idr); > > static int worker_thread(void *__worker); > > -static struct global_cwq *get_gcwq(unsigned int cpu) > +static struct worker_pool *std_worker_pools(int cpu) > { > if (cpu != WORK_CPU_UNBOUND) > - return &per_cpu(global_cwq, cpu); > + return per_cpu(cpu_std_worker_pools, cpu); > else > - return &unbound_global_cwq; > + return unbound_std_worker_pools; > } > > static int std_worker_pool_pri(struct worker_pool *pool) > { > - return pool - get_gcwq(pool->cpu)->pools; > + return pool - std_worker_pools(pool->cpu); > } > > /* allocate ID and assign it to @pool */ > @@ -487,9 +477,9 @@ static struct worker_pool *worker_pool_b > > static struct worker_pool *get_std_worker_pool(int cpu, bool highpri) > { > - struct global_cwq *gcwq = get_gcwq(cpu); > + struct worker_pool *pools = std_worker_pools(cpu); > > - return &gcwq->pools[highpri]; > + return &pools[highpri]; > } > > static atomic_t *get_pool_nr_running(struct worker_pool *pool) > @@ -3269,11 +3259,9 @@ struct workqueue_struct *__alloc_workque > > for_each_cwq_cpu(cpu, wq) { > struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); > - struct global_cwq *gcwq = get_gcwq(cpu); > - int pool_idx = (bool)(flags & WQ_HIGHPRI); > > BUG_ON((unsigned long)cwq & WORK_STRUCT_FLAG_MASK); > - cwq->pool = &gcwq->pools[pool_idx]; > + cwq->pool = get_std_worker_pool(cpu, flags & WQ_HIGHPRI); > cwq->wq = wq; > cwq->flush_color = -1; > cwq->max_active = max_active; > --- a/kernel/workqueue_internal.h > +++ b/kernel/workqueue_internal.h > @@ -10,7 +10,6 @@ > #include <linux/workqueue.h> > #include <linux/kthread.h> > > -struct global_cwq; > struct worker_pool; > > /* > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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