[2.6.6-mm4-ff1] I/O context isolation

From: FabF
Date: Fri May 21 2004 - 02:26:51 EST

Jens,

Here's ff1 patchset to have generic I/O context.
ff1 : Export io context operations from blkdev/ll_rw_blk (ok)
ff2 : Make io_context generic plateform by importing IO stuff from
as_io.

AFAICS, cfq_queue for instance could disappear when using io_context
but I think elv_data should remain elevator side....
I don't want to go in the wild here so if you've got suggestions, don't
hesitate ;)

Regards,
FabF
diff -Naur linux-2.6.6mm4/Changelog linux-2.6.6mm4ff1/Changelog
--- linux-2.6.6mm4/Changelog 1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.6mm4ff1/Changelog 2004-05-20 17:35:40.000000000 +0200
@@ -0,0 +1,5 @@
+2.6.6-mm4-ff1
+-------------
+Guideline : io/scheduler redesign
+
+> Extract io_context operations & ds from blkdev (FabF)
diff -Naur linux-2.6.6mm4/Makefile linux-2.6.6mm4ff1/Makefile
--- linux-2.6.6mm4/Makefile 2004-05-19 23:30:25.000000000 +0200
+++ linux-2.6.6mm4ff1/Makefile 2004-05-20 17:30:28.000000000 +0200
@@ -1,7 +1,7 @@
VERSION = 2
PATCHLEVEL = 6
SUBLEVEL = 6
-EXTRAVERSION = -mm4
+EXTRAVERSION = -mm4ff1
NAME=Zonked Quokka

# *DOCUMENTATION*
diff -Naur linux-2.6.6mm4/Todo linux-2.6.6mm4ff1/Todo
--- linux-2.6.6mm4/Todo 1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.6mm4ff1/Todo 2004-05-20 17:36:14.000000000 +0200
@@ -0,0 +1,4 @@
+
+< Extract as_io_context from blkdev.h
+< Documentation synch
+
diff -Naur linux-2.6.6mm4/drivers/block/Makefile linux-2.6.6mm4ff1/drivers/block/Makefile
--- linux-2.6.6mm4/drivers/block/Makefile 2004-05-10 04:33:13.000000000 +0200
+++ linux-2.6.6mm4ff1/drivers/block/Makefile 2004-05-20 12:45:55.000000000 +0200
@@ -13,7 +13,7 @@
# kblockd threads
#

-obj-y := elevator.o ll_rw_blk.o ioctl.o genhd.o scsi_ioctl.o
+obj-y := elevator.o io_context.o ll_rw_blk.o ioctl.o genhd.o scsi_ioctl.o

obj-$(CONFIG_IOSCHED_NOOP) += noop-iosched.o
obj-$(CONFIG_IOSCHED_AS) += as-iosched.o
diff -Naur linux-2.6.6mm4/drivers/block/as-iosched.c linux-2.6.6mm4ff1/drivers/block/as-iosched.c
--- linux-2.6.6mm4/drivers/block/as-iosched.c 2004-05-19 23:30:07.000000000 +0200
+++ linux-2.6.6mm4ff1/drivers/block/as-iosched.c 2004-05-20 13:08:42.000000000 +0200
@@ -9,6 +9,7 @@
*/
#include <linux/kernel.h>
#include <linux/fs.h>
+#include <linux/io_context.h>
#include <linux/blkdev.h>
#include <linux/elevator.h>
#include <linux/bio.h>
diff -Naur linux-2.6.6mm4/drivers/block/io_context.c linux-2.6.6mm4ff1/drivers/block/io_context.c
--- linux-2.6.6mm4/drivers/block/io_context.c 1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.6mm4ff1/drivers/block/io_context.c 2004-05-20 17:25:23.000000000 +0200
@@ -0,0 +1,114 @@
+/*
+ * linux/drivers/block/io_context.c
+ *
+ * io_context isolation, FabF - may 2004
+ */
+
+#include <linux/io_context.h>
+
+kmem_cache_t *iocontext_cachep;
+
+/*
+ * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
+ * will cause the process to be a "batcher" on all queues in the system. This
+ * is the behaviour we want though - once it gets a wakeup it should be given
+ * a nice run.
+ */
+void ioc_set_batching(struct io_context *ioc)
+{
+ if (!ioc || ioc_batching(ioc))
+ return;
+
+ ioc->nr_batch_requests = BLK_BATCH_REQ;
+ ioc->last_waited = jiffies;
+}
+
+/*
+ * IO Context helper functions
+ */
+void put_io_context(struct io_context *ioc)
+{
+ if (ioc == NULL)
+ return;
+
+ BUG_ON(atomic_read(&ioc->refcount) == 0);
+
+ if (atomic_dec_and_test(&ioc->refcount)) {
+ if (ioc->aic && ioc->aic->dtor)
+ ioc->aic->dtor(ioc->aic);
+ kmem_cache_free(iocontext_cachep, ioc);
+ }
+}
+
+/* Called by the exitting task */
+void exit_io_context(void)
+{
+ unsigned long flags;
+ struct io_context *ioc;
+
+ local_irq_save(flags);
+ ioc = current->io_context;
+ if (ioc) {
+ if (ioc->aic && ioc->aic->exit)
+ ioc->aic->exit(ioc->aic);
+ put_io_context(ioc);
+ current->io_context = NULL;
+ } else
+ WARN_ON(1);
+ local_irq_restore(flags);
+}
+
+/*
+ * If the current task has no IO context then create one and initialise it.
+ * If it does have a context, take a ref on it.
+ *
+ * This is always called in the context of the task which submitted the I/O.
+ * But weird things happen, so we disable local interrupts to ensure exclusive
+ * access to *current.
+ */
+struct io_context *get_io_context(int gfp_flags)
+{
+ struct task_struct *tsk = current;
+ unsigned long flags;
+ struct io_context *ret;
+
+ local_irq_save(flags);
+ ret = tsk->io_context;
+ if (ret == NULL) {
+ ret = kmem_cache_alloc(iocontext_cachep, GFP_ATOMIC);
+ if (ret) {
+ atomic_set(&ret->refcount, 1);
+ ret->pid = tsk->pid;
+ ret->last_waited = jiffies; /* doesn't matter... */
+ ret->nr_batch_requests = 0; /* because this is 0 */
+ ret->aic = NULL;
+ tsk->io_context = ret;
+ }
+ }
+ if (ret)
+ atomic_inc(&ret->refcount);
+ local_irq_restore(flags);
+ return ret;
+}
+
+void copy_io_context(struct io_context **pdst, struct io_context **psrc)
+{
+ struct io_context *src = *psrc;
+ struct io_context *dst = *pdst;
+
+ if (src) {
+ BUG_ON(atomic_read(&src->refcount) == 0);
+ atomic_inc(&src->refcount);
+ put_io_context(dst);
+ *pdst = src;
+ }
+}
+
+void swap_io_context(struct io_context **ioc1, struct io_context **ioc2)
+{
+ struct io_context *temp;
+ temp = *ioc1;
+ *ioc1 = *ioc2;
+ *ioc2 = temp;
+}
+
diff -Naur linux-2.6.6mm4/drivers/block/ll_rw_blk.c linux-2.6.6mm4ff1/drivers/block/ll_rw_blk.c
--- linux-2.6.6mm4/drivers/block/ll_rw_blk.c 2004-05-19 23:30:07.000000000 +0200
+++ linux-2.6.6mm4ff1/drivers/block/ll_rw_blk.c 2004-05-20 13:03:47.000000000 +0200
@@ -7,6 +7,7 @@
* Queue request tables / lock, selectable elevator, Jens Axboe <axboe@xxxxxxx>
* kernel-doc documentation started by NeilBrown <neilb@xxxxxxxxxxxxxxx> - July2000
* bio rewrite, highmem i/o, etc, Jens Axboe <axboe@xxxxxxx> - may 2001
+ * io_context isolation, FabF - may 2004
*/

/*
@@ -28,6 +29,7 @@
#include <linux/slab.h>
#include <linux/swap.h>
#include <linux/writeback.h>
+#include <linux/io_context.h>

/*
* for max sense size
@@ -47,11 +49,6 @@
*/
static kmem_cache_t *requestq_cachep;

-/*
- * For io context allocations
- */
-static kmem_cache_t *iocontext_cachep;
-
static wait_queue_head_t congestion_wqh[2] = {
__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
@@ -67,12 +64,6 @@
EXPORT_SYMBOL(blk_max_low_pfn);
EXPORT_SYMBOL(blk_max_pfn);

-/* Amount of time in which a process may batch requests */
-#define BLK_BATCH_TIME (HZ/50UL)
-
-/* Number of requests a "batching" process may submit */
-#define BLK_BATCH_REQ 32
-
/*
* Return the threshold (number of used requests) at which the queue is
* considered to be congested. It include a little hysteresis to keep the
@@ -1482,40 +1473,6 @@
}

/*
- * ioc_batching returns true if the ioc is a valid batching request and
- * should be given priority access to a request.
- */
-static inline int ioc_batching(struct io_context *ioc)
-{
- if (!ioc)
- return 0;
-
- /*
- * Make sure the process is able to allocate at least 1 request
- * even if the batch times out, otherwise we could theoretically
- * lose wakeups.
- */
- return ioc->nr_batch_requests == BLK_BATCH_REQ ||
- (ioc->nr_batch_requests > 0
- && time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
-}
-
-/*
- * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
- * will cause the process to be a "batcher" on all queues in the system. This
- * is the behaviour we want though - once it gets a wakeup it should be given
- * a nice run.
- */
-void ioc_set_batching(struct io_context *ioc)
-{
- if (!ioc || ioc_batching(ioc))
- return;
-
- ioc->nr_batch_requests = BLK_BATCH_REQ;
- ioc->last_waited = jiffies;
-}
-
-/*
* A request has just been released. Account for it, update the full and
* congestion status, wake up any waiters. Called under q->queue_lock.
*/
@@ -2845,96 +2802,6 @@
}

/*
- * IO Context helper functions
- */
-void put_io_context(struct io_context *ioc)
-{
- if (ioc == NULL)
- return;
-
- BUG_ON(atomic_read(&ioc->refcount) == 0);
-
- if (atomic_dec_and_test(&ioc->refcount)) {
- if (ioc->aic && ioc->aic->dtor)
- ioc->aic->dtor(ioc->aic);
- kmem_cache_free(iocontext_cachep, ioc);
- }
-}
-
-/* Called by the exitting task */
-void exit_io_context(void)
-{
- unsigned long flags;
- struct io_context *ioc;
-
- local_irq_save(flags);
- ioc = current->io_context;
- if (ioc) {
- if (ioc->aic && ioc->aic->exit)
- ioc->aic->exit(ioc->aic);
- put_io_context(ioc);
- current->io_context = NULL;
- } else
- WARN_ON(1);
- local_irq_restore(flags);
-}
-
-/*
- * If the current task has no IO context then create one and initialise it.
- * If it does have a context, take a ref on it.
- *
- * This is always called in the context of the task which submitted the I/O.
- * But weird things happen, so we disable local interrupts to ensure exclusive
- * access to *current.
- */
-struct io_context *get_io_context(int gfp_flags)
-{
- struct task_struct *tsk = current;
- unsigned long flags;
- struct io_context *ret;
-
- local_irq_save(flags);
- ret = tsk->io_context;
- if (ret == NULL) {
- ret = kmem_cache_alloc(iocontext_cachep, GFP_ATOMIC);
- if (ret) {
- atomic_set(&ret->refcount, 1);
- ret->pid = tsk->pid;
- ret->last_waited = jiffies; /* doesn't matter... */
- ret->nr_batch_requests = 0; /* because this is 0 */
- ret->aic = NULL;
- tsk->io_context = ret;
- }
- }
- if (ret)
- atomic_inc(&ret->refcount);
- local_irq_restore(flags);
- return ret;
-}
-
-void copy_io_context(struct io_context **pdst, struct io_context **psrc)
-{
- struct io_context *src = *psrc;
- struct io_context *dst = *pdst;
-
- if (src) {
- BUG_ON(atomic_read(&src->refcount) == 0);
- atomic_inc(&src->refcount);
- put_io_context(dst);
- *pdst = src;
- }
-}
-
-void swap_io_context(struct io_context **ioc1, struct io_context **ioc2)
-{
- struct io_context *temp;
- temp = *ioc1;
- *ioc1 = *ioc2;
- *ioc2 = temp;
-}
-
-
-/*
* sysfs parts below
*/
struct queue_sysfs_entry {
diff -Naur linux-2.6.6mm4/include/linux/blkdev.h linux-2.6.6mm4ff1/include/linux/blkdev.h
--- linux-2.6.6mm4/include/linux/blkdev.h 2004-05-19 23:30:24.000000000 +0200
+++ linux-2.6.6mm4ff1/include/linux/blkdev.h 2004-05-20 17:25:03.000000000 +0200
@@ -25,56 +25,8 @@

#define BLKDEV_MIN_RQ 4
#define BLKDEV_MAX_RQ 128 /* Default maximum */
-
-/*
- * This is the per-process anticipatory I/O scheduler state.
- */
-struct as_io_context {
- spinlock_t lock;
-
- void (*dtor)(struct as_io_context *aic); /* destructor */
- void (*exit)(struct as_io_context *aic); /* called on task exit */
-
- unsigned long state;
- atomic_t nr_queued; /* queued reads & sync writes */
- atomic_t nr_dispatched; /* number of requests gone to the drivers */
-
- /* IO History tracking */
- /* Thinktime */
- unsigned long last_end_request;
- unsigned long ttime_total;
- unsigned long ttime_samples;
- unsigned long ttime_mean;
- /* Layout pattern */
- unsigned int seek_samples;
- sector_t last_request_pos;
- u64 seek_total;
- sector_t seek_mean;
-};
-
-/*
- * This is the per-process I/O subsystem state. It is refcounted and
- * kmalloc'ed. Currently all fields are modified in process io context
- * (apart from the atomic refcount), so require no locking.
- */
-struct io_context {
- atomic_t refcount;
- pid_t pid;
-
- /*
- * For request batching
- */
- unsigned long last_waited; /* Time last woken after wait for request */
- int nr_batch_requests; /* Number of requests left in the batch */
-
- struct as_io_context *aic;
-};
-
-void put_io_context(struct io_context *ioc);
-void exit_io_context(void);
-struct io_context *get_io_context(int gfp_flags);
-void copy_io_context(struct io_context **pdst, struct io_context **psrc);
-void swap_io_context(struct io_context **ioc1, struct io_context **ioc2);
+#define BLK_BATCH_TIME (HZ/50UL) /*Amount of time in which a process may batch requests */
+#define BLK_BATCH_REQ 32 /* Number of requests a "batching" process may submit */

struct request_list {
int count[2];
diff -Naur linux-2.6.6mm4/include/linux/io_context.h linux-2.6.6mm4ff1/include/linux/io_context.h
--- linux-2.6.6mm4/include/linux/io_context.h 1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.6mm4ff1/include/linux/io_context.h 2004-05-20 17:25:01.000000000 +0200
@@ -0,0 +1,84 @@
+#ifndef _LINUX_IO_CONTEXT_H
+#define _LINUX_IO_CONTEXT_H
+
+#include <linux/timer.h>
+#include <linux/blkdev.h>
+
+/*
+ * This is the per-process anticipatory I/O scheduler state.
+ */
+
+struct as_io_context {
+ spinlock_t lock;
+
+ void (*dtor)(struct as_io_context *aic); /* destructor */
+ void (*exit)(struct as_io_context *aic); /* called on task exit */
+
+ unsigned long state;
+ atomic_t nr_queued; /* queued reads & sync writes */
+ atomic_t nr_dispatched; /* number of requests gone to the drivers */
+
+ /* IO History tracking */
+ /* Thinktime */
+ unsigned long last_end_request;
+ unsigned long ttime_total;
+ unsigned long ttime_samples;
+ unsigned long ttime_mean;
+ /* Layout pattern */
+ unsigned int seek_samples;
+ sector_t last_request_pos;
+ u64 seek_total;
+ sector_t seek_mean;
+};
+
+/*
+ * This is the per-process I/O subsystem state. It is refcounted and
+ * kmalloc'ed. Currently all fields are modified in process io context
+ * (apart from the atomic refcount), so require no locking.
+ */
+struct io_context {
+ atomic_t refcount;
+ pid_t pid;
+
+ /*
+ * For request batching
+ */
+ unsigned long last_waited; /* Time last woken after wait for request */
+ int nr_batch_requests; /* Number of requests left in the batch */
+
+ struct as_io_context *aic;
+};
+
+extern kmem_cache_t *iocontext_cachep;
+
+/*
+ * For io context allocations
+ */
+static inline int ioc_batching(struct io_context *ioc);
+void ioc_set_batching(struct io_context *ioc);
+void put_io_context(struct io_context *ioc);
+void exit_io_context(void);
+struct io_context *get_io_context(int gfp_flags);
+void copy_io_context(struct io_context **pdst, struct io_context **psrc);
+void swap_io_context(struct io_context **ioc1, struct io_context **ioc2);
+
+/*
+ * ioc_batching returns true if the ioc is a valid batching request and
+ * should be given priority access to a request.
+ */
+static inline int ioc_batching(struct io_context *ioc)
+{
+ if (!ioc)
+ return 0;
+
+ /*
+ * Make sure the process is able to allocate at least 1 request
+ * even if the batch times out, otherwise we could theoretically
+ * lose wakeups.
+ */
+ return ioc->nr_batch_requests == BLK_BATCH_REQ ||
+ (ioc->nr_batch_requests > 0
+ && time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
+}
+
+#endif