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Subject[PATCH 29/29] ioat2, 3: cacheline align software descriptor allocations
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All the necessary fields for handling an ioat2,3 ring entry can fit into
one cacheline. Move ->len prior to ->txd in struct ioat_ring_ent, and
move allocation of these entries to a hw-cache-aligned kmem cache to
reduce the number of cachelines dirtied for descriptor management.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
drivers/dma/ioat/dma_v2.c | 5 +++--
drivers/dma/ioat/dma_v2.h | 3 ++-
drivers/dma/ioat/pci.c | 16 +++++++++++++++-
3 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/drivers/dma/ioat/dma_v2.c b/drivers/dma/ioat/dma_v2.c
index 9ea1a47..f0c4876 100644
--- a/drivers/dma/ioat/dma_v2.c
+++ b/drivers/dma/ioat/dma_v2.c
@@ -400,11 +400,12 @@ static struct ioat_ring_ent *ioat2_alloc_ring_ent(struct dma_chan *chan, gfp_t f
return NULL;
memset(hw, 0, sizeof(*hw));

- desc = kzalloc(sizeof(*desc), flags);
+ desc = kmem_cache_alloc(ioat2_cache, flags);
if (!desc) {
pci_pool_free(dma->dma_pool, hw, phys);
return NULL;
}
+ memset(desc, 0, sizeof(*desc));

dma_async_tx_descriptor_init(&desc->txd, chan);
desc->txd.tx_submit = ioat2_tx_submit_unlock;
@@ -419,7 +420,7 @@ static void ioat2_free_ring_ent(struct ioat_ring_ent *desc, struct dma_chan *cha

dma = to_ioatdma_device(chan->device);
pci_pool_free(dma->dma_pool, desc->hw, desc->txd.phys);
- kfree(desc);
+ kmem_cache_free(ioat2_cache, desc);
}

static struct ioat_ring_ent **ioat2_alloc_ring(struct dma_chan *c, int order, gfp_t flags)
diff --git a/drivers/dma/ioat/dma_v2.h b/drivers/dma/ioat/dma_v2.h
index 9baa3d6..ac00adc 100644
--- a/drivers/dma/ioat/dma_v2.h
+++ b/drivers/dma/ioat/dma_v2.h
@@ -116,8 +116,8 @@ static inline u16 ioat2_xferlen_to_descs(struct ioat2_dma_chan *ioat, size_t len

struct ioat_ring_ent {
struct ioat_dma_descriptor *hw;
- struct dma_async_tx_descriptor txd;
size_t len;
+ struct dma_async_tx_descriptor txd;
#ifdef DEBUG
int id;
#endif
@@ -143,4 +143,5 @@ int __devinit ioat2_dma_probe(struct ioatdma_device *dev, int dca);
int __devinit ioat3_dma_probe(struct ioatdma_device *dev, int dca);
struct dca_provider * __devinit ioat2_dca_init(struct pci_dev *pdev, void __iomem *iobase);
struct dca_provider * __devinit ioat3_dca_init(struct pci_dev *pdev, void __iomem *iobase);
+extern struct kmem_cache *ioat2_cache;
#endif /* IOATDMA_V2_H */
diff --git a/drivers/dma/ioat/pci.c b/drivers/dma/ioat/pci.c
index c4e4322..61086c6 100644
--- a/drivers/dma/ioat/pci.c
+++ b/drivers/dma/ioat/pci.c
@@ -69,6 +69,8 @@ static int ioat_dca_enabled = 1;
module_param(ioat_dca_enabled, int, 0644);
MODULE_PARM_DESC(ioat_dca_enabled, "control support of dca service (default: 1)");

+struct kmem_cache *ioat2_cache;
+
#define DRV_NAME "ioatdma"

static struct pci_driver ioat_pci_driver = {
@@ -168,12 +170,24 @@ static void __devexit ioat_remove(struct pci_dev *pdev)

static int __init ioat_init_module(void)
{
- return pci_register_driver(&ioat_pci_driver);
+ int err;
+
+ ioat2_cache = kmem_cache_create("ioat2", sizeof(struct ioat_ring_ent),
+ 0, SLAB_HWCACHE_ALIGN, NULL);
+ if (!ioat2_cache)
+ return -ENOMEM;
+
+ err = pci_register_driver(&ioat_pci_driver);
+ if (err)
+ kmem_cache_destroy(ioat2_cache);
+
+ return err;
}
module_init(ioat_init_module);

static void __exit ioat_exit_module(void)
{
pci_unregister_driver(&ioat_pci_driver);
+ kmem_cache_destroy(ioat2_cache);
}
module_exit(ioat_exit_module);


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