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i915: use io-mapping interfaces instead of a variety of mapping kludges
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Impact: optimize/clean-up the IO mapping implementation of the i915 DRM driver

Switch the i915 device aperture mapping to the io-mapping interface, taking
advantage of the cleaner API to extend it across all of the mapping uses,
including both pwrite and relocation updates.

This dramatically improves performance on 64-bit kernels which were using
the same slow path as 32-bit non-HIGHMEM kernels prior to this patch.

Signed-off-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Keith Packard authored and Ingo Molnar committed Oct 31, 2008
1 parent 9663f2e commit 0839ccb
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Showing 2 changed files with 83 additions and 94 deletions.
3 changes: 3 additions & 0 deletions drivers/gpu/drm/i915/i915_drv.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,7 @@
#define _I915_DRV_H_

#include "i915_reg.h"
#include <linux/io-mapping.h>

/* General customization:
*/
Expand Down Expand Up @@ -246,6 +247,8 @@ typedef struct drm_i915_private {
struct {
struct drm_mm gtt_space;

struct io_mapping *gtt_mapping;

/**
* List of objects currently involved in rendering from the
* ringbuffer.
Expand Down
174 changes: 80 additions & 94 deletions drivers/gpu/drm/i915/i915_gem.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -171,35 +171,50 @@ i915_gem_pread_ioctl(struct drm_device *dev, void *data,
return 0;
}

/*
* Try to write quickly with an atomic kmap. Return true on success.
*
* If this fails (which includes a partial write), we'll redo the whole
* thing with the slow version.
*
* This is a workaround for the low performance of iounmap (approximate
* 10% cpu cost on normal 3D workloads). kmap_atomic on HIGHMEM kernels
* happens to let us map card memory without taking IPIs. When the vmap
* rework lands we should be able to dump this hack.
/* This is the fast write path which cannot handle
* page faults in the source data
*/
static inline int fast_user_write(unsigned long pfn, char __user *user_data,
int l, int o)

static inline int
fast_user_write(struct io_mapping *mapping,
loff_t page_base, int page_offset,
char __user *user_data,
int length)
{
#ifdef CONFIG_HIGHMEM
unsigned long unwritten;
char *vaddr_atomic;
unsigned long unwritten;

vaddr_atomic = kmap_atomic_pfn(pfn, KM_USER0);
#if WATCH_PWRITE
DRM_INFO("pwrite i %d o %d l %d pfn %ld vaddr %p\n",
i, o, l, pfn, vaddr_atomic);
#endif
unwritten = __copy_from_user_inatomic_nocache(vaddr_atomic + o, user_data, l);
kunmap_atomic(vaddr_atomic, KM_USER0);
return !unwritten;
#else
vaddr_atomic = io_mapping_map_atomic_wc(mapping, page_base);
unwritten = __copy_from_user_inatomic_nocache(vaddr_atomic + page_offset,
user_data, length);
io_mapping_unmap_atomic(vaddr_atomic);
if (unwritten)
return -EFAULT;
return 0;
}

/* Here's the write path which can sleep for
* page faults
*/

static inline int
slow_user_write(struct io_mapping *mapping,
loff_t page_base, int page_offset,
char __user *user_data,
int length)
{
char __iomem *vaddr;
unsigned long unwritten;

vaddr = io_mapping_map_wc(mapping, page_base);
if (vaddr == NULL)
return -EFAULT;
unwritten = __copy_from_user(vaddr + page_offset,
user_data, length);
io_mapping_unmap(vaddr);
if (unwritten)
return -EFAULT;
return 0;
#endif
}

static int
Expand All @@ -208,10 +223,12 @@ i915_gem_gtt_pwrite(struct drm_device *dev, struct drm_gem_object *obj,
struct drm_file *file_priv)
{
struct drm_i915_gem_object *obj_priv = obj->driver_private;
drm_i915_private_t *dev_priv = dev->dev_private;
ssize_t remain;
loff_t offset;
loff_t offset, page_base;
char __user *user_data;
int ret = 0;
int page_offset, page_length;
int ret;

user_data = (char __user *) (uintptr_t) args->data_ptr;
remain = args->size;
Expand All @@ -235,57 +252,37 @@ i915_gem_gtt_pwrite(struct drm_device *dev, struct drm_gem_object *obj,
obj_priv->dirty = 1;

while (remain > 0) {
unsigned long pfn;
int i, o, l;

/* Operation in this page
*
* i = page number
* o = offset within page
* l = bytes to copy
* page_base = page offset within aperture
* page_offset = offset within page
* page_length = bytes to copy for this page
*/
i = offset >> PAGE_SHIFT;
o = offset & (PAGE_SIZE-1);
l = remain;
if ((o + l) > PAGE_SIZE)
l = PAGE_SIZE - o;

pfn = (dev->agp->base >> PAGE_SHIFT) + i;

if (!fast_user_write(pfn, user_data, l, o)) {
unsigned long unwritten;
char __iomem *vaddr;

vaddr = ioremap_wc(pfn << PAGE_SHIFT, PAGE_SIZE);
#if WATCH_PWRITE
DRM_INFO("pwrite slow i %d o %d l %d "
"pfn %ld vaddr %p\n",
i, o, l, pfn, vaddr);
#endif
if (vaddr == NULL) {
ret = -EFAULT;
goto fail;
}
unwritten = __copy_from_user(vaddr + o, user_data, l);
#if WATCH_PWRITE
DRM_INFO("unwritten %ld\n", unwritten);
#endif
iounmap(vaddr);
if (unwritten) {
ret = -EFAULT;
page_base = (offset & ~(PAGE_SIZE-1));
page_offset = offset & (PAGE_SIZE-1);
page_length = remain;
if ((page_offset + remain) > PAGE_SIZE)
page_length = PAGE_SIZE - page_offset;

ret = fast_user_write (dev_priv->mm.gtt_mapping, page_base,
page_offset, user_data, page_length);

/* If we get a fault while copying data, then (presumably) our
* source page isn't available. In this case, use the
* non-atomic function
*/
if (ret) {
ret = slow_user_write (dev_priv->mm.gtt_mapping,
page_base, page_offset,
user_data, page_length);
if (ret)
goto fail;
}
}

remain -= l;
user_data += l;
offset += l;
remain -= page_length;
user_data += page_length;
offset += page_length;
}
#if WATCH_PWRITE && 1
i915_gem_clflush_object(obj);
i915_gem_dump_object(obj, args->offset + args->size, __func__, ~0);
i915_gem_clflush_object(obj);
#endif

fail:
i915_gem_object_unpin(obj);
Expand Down Expand Up @@ -1503,12 +1500,12 @@ i915_gem_object_pin_and_relocate(struct drm_gem_object *obj,
struct drm_i915_gem_exec_object *entry)
{
struct drm_device *dev = obj->dev;
drm_i915_private_t *dev_priv = dev->dev_private;
struct drm_i915_gem_relocation_entry reloc;
struct drm_i915_gem_relocation_entry __user *relocs;
struct drm_i915_gem_object *obj_priv = obj->driver_private;
int i, ret;
uint32_t last_reloc_offset = -1;
void __iomem *reloc_page = NULL;
void __iomem *reloc_page;

/* Choose the GTT offset for our buffer and put it there. */
ret = i915_gem_object_pin(obj, (uint32_t) entry->alignment);
Expand Down Expand Up @@ -1631,26 +1628,11 @@ i915_gem_object_pin_and_relocate(struct drm_gem_object *obj,
* perform.
*/
reloc_offset = obj_priv->gtt_offset + reloc.offset;
if (reloc_page == NULL ||
(last_reloc_offset & ~(PAGE_SIZE - 1)) !=
(reloc_offset & ~(PAGE_SIZE - 1))) {
if (reloc_page != NULL)
iounmap(reloc_page);

reloc_page = ioremap_wc(dev->agp->base +
(reloc_offset &
~(PAGE_SIZE - 1)),
PAGE_SIZE);
last_reloc_offset = reloc_offset;
if (reloc_page == NULL) {
drm_gem_object_unreference(target_obj);
i915_gem_object_unpin(obj);
return -ENOMEM;
}
}

reloc_page = io_mapping_map_atomic_wc(dev_priv->mm.gtt_mapping,
(reloc_offset &
~(PAGE_SIZE - 1)));
reloc_entry = (uint32_t __iomem *)(reloc_page +
(reloc_offset & (PAGE_SIZE - 1)));
(reloc_offset & (PAGE_SIZE - 1)));
reloc_val = target_obj_priv->gtt_offset + reloc.delta;

#if WATCH_BUF
Expand All @@ -1659,6 +1641,7 @@ i915_gem_object_pin_and_relocate(struct drm_gem_object *obj,
readl(reloc_entry), reloc_val);
#endif
writel(reloc_val, reloc_entry);
io_mapping_unmap_atomic(reloc_page);

/* Write the updated presumed offset for this entry back out
* to the user.
Expand All @@ -1674,9 +1657,6 @@ i915_gem_object_pin_and_relocate(struct drm_gem_object *obj,
drm_gem_object_unreference(target_obj);
}

if (reloc_page != NULL)
iounmap(reloc_page);

#if WATCH_BUF
if (0)
i915_gem_dump_object(obj, 128, __func__, ~0);
Expand Down Expand Up @@ -2518,6 +2498,10 @@ i915_gem_entervt_ioctl(struct drm_device *dev, void *data,
if (ret != 0)
return ret;

dev_priv->mm.gtt_mapping = io_mapping_create_wc(dev->agp->base,
dev->agp->agp_info.aper_size
* 1024 * 1024);

mutex_lock(&dev->struct_mutex);
BUG_ON(!list_empty(&dev_priv->mm.active_list));
BUG_ON(!list_empty(&dev_priv->mm.flushing_list));
Expand All @@ -2535,11 +2519,13 @@ int
i915_gem_leavevt_ioctl(struct drm_device *dev, void *data,
struct drm_file *file_priv)
{
drm_i915_private_t *dev_priv = dev->dev_private;
int ret;

ret = i915_gem_idle(dev);
drm_irq_uninstall(dev);

io_mapping_free(dev_priv->mm.gtt_mapping);
return ret;
}

Expand Down

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