From 31ce479ecab2638892f4fba191d300aa5a9d9746 Mon Sep 17 00:00:00 2001 From: Arianna Avanzini <73628@studenti.unimore.it> Date: Mon, 12 Sep 2011 22:40:31 +0200 Subject: [PATCH 1/3] block: prepare I/O context code for BFQ-v3 for 3.0 BFQ uses struct cfq_io_context to store its per-process per-device data, reusing the same code for cic handling of CFQ. The code is not shared ATM to minimize the impact of these patches. This patch introduces a new hlist to each io_context to store all the cic's allocated by BFQ to allow calling the right destructor on module unload; the radix tree used for cic lookup needs to be duplicated because it can contain dead keys inserted by a scheduler and later retrieved by the other one. Update the io_context exit and free paths to take care also of the BFQ cic's. Change the type of cfqq inside struct cfq_io_context to void * to use it also for BFQ per-queue data. A new bfq-specific ioprio_changed field is necessary, too, to avoid clobbering cfq's one, so switch ioprio_changed to a bitmap, with one element per scheduler. Signed-off-by: Fabio Checconi Signed-off-by: Paolo Valente Signed-off-by: Arianna Avanzini --- block/Kconfig.iosched | 26 ++++++++++++++++++++++++++ block/blk-ioc.c | 30 +++++++++++++++++------------- block/cfq-iosched.c | 10 +++++++--- fs/ioprio.c | 9 +++++++-- include/linux/iocontext.h | 18 +++++++++++++++--- 5 files changed, 72 insertions(+), 21 deletions(-) diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched index 3199b76..5905452 100644 --- a/block/Kconfig.iosched +++ b/block/Kconfig.iosched @@ -43,6 +43,28 @@ config CFQ_GROUP_IOSCHED ---help--- Enable group IO scheduling in CFQ. +config IOSCHED_BFQ + tristate "BFQ I/O scheduler" + depends on EXPERIMENTAL + default n + ---help--- + The BFQ I/O scheduler tries to distribute bandwidth among + all processes according to their weights. + It aims at distributing the bandwidth as desired, independently of + the disk parameters and with any workload. It also tries to + guarantee low latency to interactive and soft real-time + applications. If compiled built-in (saying Y here), BFQ can + be configured to support hierarchical scheduling. + +config CGROUP_BFQIO + bool "BFQ hierarchical scheduling support" + depends on CGROUPS && IOSCHED_BFQ=y + default n + ---help--- + Enable hierarchical scheduling in BFQ, using the cgroups + filesystem interface. The name of the subsystem will be + bfqio. + choice prompt "Default I/O scheduler" default DEFAULT_CFQ @@ -56,6 +78,9 @@ choice config DEFAULT_CFQ bool "CFQ" if IOSCHED_CFQ=y + config DEFAULT_BFQ + bool "BFQ" if IOSCHED_BFQ=y + config DEFAULT_NOOP bool "No-op" @@ -65,6 +90,7 @@ config DEFAULT_IOSCHED string default "deadline" if DEFAULT_DEADLINE default "cfq" if DEFAULT_CFQ + default "bfq" if DEFAULT_BFQ default "noop" if DEFAULT_NOOP endmenu diff --git a/block/blk-ioc.c b/block/blk-ioc.c index 342eae9..21f13b1 100644 --- a/block/blk-ioc.c +++ b/block/blk-ioc.c @@ -5,6 +5,7 @@ #include #include #include +#include #include #include /* for max_pfn/max_low_pfn */ #include @@ -16,13 +17,12 @@ */ static struct kmem_cache *iocontext_cachep; -static void cfq_dtor(struct io_context *ioc) +static void hlist_sched_dtor(struct io_context *ioc, struct hlist_head *list) { - if (!hlist_empty(&ioc->cic_list)) { + if (!hlist_empty(list)) { struct cfq_io_context *cic; - cic = hlist_entry(ioc->cic_list.first, struct cfq_io_context, - cic_list); + cic = hlist_entry(list->first, struct cfq_io_context, cic_list); cic->dtor(ioc); } } @@ -40,7 +40,9 @@ int put_io_context(struct io_context *ioc) if (atomic_long_dec_and_test(&ioc->refcount)) { rcu_read_lock(); - cfq_dtor(ioc); + + hlist_sched_dtor(ioc, &ioc->cic_list); + hlist_sched_dtor(ioc, &ioc->bfq_cic_list); rcu_read_unlock(); kmem_cache_free(iocontext_cachep, ioc); @@ -50,15 +52,14 @@ int put_io_context(struct io_context *ioc) } EXPORT_SYMBOL(put_io_context); -static void cfq_exit(struct io_context *ioc) +static void hlist_sched_exit(struct io_context *ioc, struct hlist_head *list) { rcu_read_lock(); - if (!hlist_empty(&ioc->cic_list)) { + if (!hlist_empty(list)) { struct cfq_io_context *cic; - cic = hlist_entry(ioc->cic_list.first, struct cfq_io_context, - cic_list); + cic = hlist_entry(list->first, struct cfq_io_context, cic_list); cic->exit(ioc); } rcu_read_unlock(); @@ -74,9 +75,10 @@ void exit_io_context(struct task_struct *task) task->io_context = NULL; task_unlock(task); - if (atomic_dec_and_test(&ioc->nr_tasks)) - cfq_exit(ioc); - + if (atomic_dec_and_test(&ioc->nr_tasks)) { + hlist_sched_exit(ioc, &ioc->cic_list); + hlist_sched_exit(ioc, &ioc->bfq_cic_list); + } put_io_context(ioc); } @@ -89,12 +91,14 @@ struct io_context *alloc_io_context(gfp_t gfp_flags, int node) atomic_long_set(&ret->refcount, 1); atomic_set(&ret->nr_tasks, 1); spin_lock_init(&ret->lock); - ret->ioprio_changed = 0; + bitmap_zero(ret->ioprio_changed, IOC_IOPRIO_CHANGED_BITS); ret->ioprio = 0; ret->last_waited = 0; /* doesn't matter... */ ret->nr_batch_requests = 0; /* because this is 0 */ INIT_RADIX_TREE(&ret->radix_root, GFP_ATOMIC | __GFP_HIGH); INIT_HLIST_HEAD(&ret->cic_list); + INIT_RADIX_TREE(&ret->bfq_radix_root, GFP_ATOMIC | __GFP_HIGH); + INIT_HLIST_HEAD(&ret->bfq_cic_list); ret->ioc_data = NULL; #if defined(CONFIG_BLK_CGROUP) || defined(CONFIG_BLK_CGROUP_MODULE) ret->cgroup_changed = 0; diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index ae21919..b581793 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -2919,7 +2919,6 @@ static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic) static void cfq_ioc_set_ioprio(struct io_context *ioc) { call_for_each_cic(ioc, changed_ioprio); - ioc->ioprio_changed = 0; } static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq, @@ -3204,8 +3203,13 @@ cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask) goto err_free; out: - smp_read_barrier_depends(); - if (unlikely(ioc->ioprio_changed)) + /* + * test_and_clear_bit() implies a memory barrier, paired with + * the wmb() in fs/ioprio.c, so the value seen for ioprio is the + * new one. + */ + if (unlikely(test_and_clear_bit(IOC_CFQ_IOPRIO_CHANGED, + ioc->ioprio_changed))) cfq_ioc_set_ioprio(ioc); #ifdef CONFIG_CFQ_GROUP_IOSCHED diff --git a/fs/ioprio.c b/fs/ioprio.c index 7da2a06..95a6c2b 100644 --- a/fs/ioprio.c +++ b/fs/ioprio.c @@ -30,7 +30,7 @@ int set_task_ioprio(struct task_struct *task, int ioprio) { - int err; + int err, i; struct io_context *ioc; const struct cred *cred = current_cred(), *tcred; @@ -60,12 +60,17 @@ int set_task_ioprio(struct task_struct *task, int ioprio) err = -ENOMEM; break; } + /* let other ioc users see the new values */ + smp_wmb(); task->io_context = ioc; } while (1); if (!err) { ioc->ioprio = ioprio; - ioc->ioprio_changed = 1; + /* make sure schedulers see the new ioprio value */ + wmb(); + for (i = 0; i < IOC_IOPRIO_CHANGED_BITS; i++) + set_bit(i, ioc->ioprio_changed); } task_unlock(task); diff --git a/include/linux/iocontext.h b/include/linux/iocontext.h index b2eee89..7cbace3 100644 --- a/include/linux/iocontext.h +++ b/include/linux/iocontext.h @@ -1,14 +1,14 @@ #ifndef IOCONTEXT_H #define IOCONTEXT_H +#include #include #include -struct cfq_queue; struct cfq_io_context { void *key; - struct cfq_queue *cfqq[2]; + void *cfqq[2]; struct io_context *ioc; @@ -28,6 +28,16 @@ struct cfq_io_context { }; /* + * Indexes into the ioprio_changed bitmap. A bit set indicates that + * the corresponding I/O scheduler needs to see a ioprio update. + */ +enum { + IOC_CFQ_IOPRIO_CHANGED, + IOC_BFQ_IOPRIO_CHANGED, + IOC_IOPRIO_CHANGED_BITS +}; + +/* * I/O subsystem state of the associated processes. It is refcounted * and kmalloc'ed. These could be shared between processes. */ @@ -39,7 +49,7 @@ struct io_context { spinlock_t lock; unsigned short ioprio; - unsigned short ioprio_changed; + DECLARE_BITMAP(ioprio_changed, IOC_IOPRIO_CHANGED_BITS); #if defined(CONFIG_BLK_CGROUP) || defined(CONFIG_BLK_CGROUP_MODULE) unsigned short cgroup_changed; @@ -53,6 +63,8 @@ struct io_context { struct radix_tree_root radix_root; struct hlist_head cic_list; + struct radix_tree_root bfq_radix_root; + struct hlist_head bfq_cic_list; void __rcu *ioc_data; }; -- 1.7.4.1