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Subject[PATCH 04/15] ps3vram: Replace mutex by spinlock + list
Date
Remove the mutex serializing access to the cache.
Instead, queue up new requests on a list if the driver is busy.

This improves sequential write performance by ca. 2%.

Signed-off-by: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Cc: Jim Paris <jim@jtan.com>
---
drivers/block/ps3vram.c | 55 ++++++++++++++++++++++++++++++++++------------
1 files changed, 40 insertions(+), 15 deletions(-)
diff --git a/drivers/block/ps3vram.c b/drivers/block/ps3vram.c
index 3c9ad19..1396038 100644
--- a/drivers/block/ps3vram.c
+++ b/drivers/block/ps3vram.c
@@ -81,8 +81,8 @@ struct ps3vram_priv {

struct ps3vram_cache cache;

- /* Used to serialize cache/DMA operations */
- struct mutex lock;
+ spinlock_t lock; /* protecting list of bios */
+ struct bio *tail;
};


@@ -449,8 +449,6 @@ static int ps3vram_read(struct ps3_system_bus_device *dev, loff_t from,
offset = (unsigned int) (from & (priv->cache.page_size - 1));
avail = priv->cache.page_size - offset;

- mutex_lock(&priv->lock);
-
entry = ps3vram_cache_match(dev, from);
cached = CACHE_OFFSET + entry * priv->cache.page_size + offset;

@@ -462,8 +460,6 @@ static int ps3vram_read(struct ps3_system_bus_device *dev, loff_t from,
avail = count;
memcpy(buf, priv->xdr_buf + cached, avail);

- mutex_unlock(&priv->lock);
-
buf += avail;
count -= avail;
from += avail;
@@ -494,8 +490,6 @@ static int ps3vram_write(struct ps3_system_bus_device *dev, loff_t to,
offset = (unsigned int) (to & (priv->cache.page_size - 1));
avail = priv->cache.page_size - offset;

- mutex_lock(&priv->lock);
-
entry = ps3vram_cache_match(dev, to);
cached = CACHE_OFFSET + entry * priv->cache.page_size + offset;

@@ -509,8 +503,6 @@ static int ps3vram_write(struct ps3_system_bus_device *dev, loff_t to,

priv->cache.tags[entry].flags |= CACHE_PAGE_DIRTY;

- mutex_unlock(&priv->lock);
-
buf += avail;
count -= avail;
to += avail;
@@ -552,17 +544,17 @@ static void __devinit ps3vram_proc_init(struct ps3_system_bus_device *dev)
dev_warn(&dev->core, "failed to create /proc entry\n");
}

-static int ps3vram_make_request(struct request_queue *q, struct bio *bio)
+static struct bio *ps3vram_do_bio(struct ps3_system_bus_device *dev,
+ struct bio *bio)
{
- struct ps3_system_bus_device *dev = q->queuedata;
+ struct ps3vram_priv *priv = dev->core.driver_data;
int write = bio_data_dir(bio) == WRITE;
const char *op = write ? "write" : "read";
loff_t offset = bio->bi_sector << 9;
int error = 0;
struct bio_vec *bvec;
unsigned int i;
-
- dev_dbg(&dev->core, "%s\n", __func__);
+ struct bio *next;

bio_for_each_segment(bvec, bio, i) {
/* PS3 is ppc64, so we don't handle highmem */
@@ -593,7 +585,40 @@ static int ps3vram_make_request(struct request_queue *q, struct bio *bio)
dev_dbg(&dev->core, "%s completed\n", op);

out:
+ spin_lock_irq(&priv->lock);
+ next = bio->bi_next;
+ if (!next)
+ priv->tail = NULL;
+ else
+ bio->bi_next = NULL;
+ spin_unlock_irq(&priv->lock);
+
bio_endio(bio, error);
+ return next;
+}
+
+static int ps3vram_make_request(struct request_queue *q, struct bio *bio)
+{
+ struct ps3_system_bus_device *dev = q->queuedata;
+ struct ps3vram_priv *priv = dev->core.driver_data;
+
+ dev_dbg(&dev->core, "%s\n", __func__);
+
+ spin_lock_irq(&priv->lock);
+ if (priv->tail) {
+ priv->tail->bi_next = bio;
+ priv->tail = bio;
+ spin_unlock_irq(&priv->lock);
+ return 0;
+ }
+
+ priv->tail = bio;
+ spin_unlock_irq(&priv->lock);
+
+ do {
+ bio = ps3vram_do_bio(dev, bio);
+ } while (bio);
+
return 0;
}

@@ -613,7 +638,7 @@ static int __devinit ps3vram_probe(struct ps3_system_bus_device *dev)
goto fail;
}

- mutex_init(&priv->lock);
+ spin_lock_init(&priv->lock);
dev->core.driver_data = priv;

priv = dev->core.driver_data;
--
1.6.2.4


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