On 04/07/2018 15:25, Chris Wilson wrote:
Currently, the wc-stash used for providing flushed WC pages ready for
constructing the page directories is assumed to be protected by the
struct_mutex. However, we want to remove this global lock and so must
install a replacement global lock for accessing the global wc-stash (the
per-vm stash continues to be guarded by the vm).
We need to push ahead on this patch due to an oversight in hastily
removing the struct_mutex guard around the igt_ppgtt_alloc selftest. No
matter, it will prove very useful (i.e. will be required) in the near
future.
v2: Restore the onstack stash so that we can drop the vm->mutex in
future across the allocation.
Fixes: 1f6f00238abf ("drm/i915/selftests: Drop struct_mutex around lowlevel pggtt allocation")
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_drv.h | 2 +-
drivers/gpu/drm/i915/i915_gem_gtt.c | 152 ++++++++++++++++++----------
drivers/gpu/drm/i915/i915_gem_gtt.h | 7 +-
3 files changed, 107 insertions(+), 54 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 2cefe4c30f88..e5a0a65ec2e9 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -952,7 +952,7 @@ struct i915_gem_mm {
/**
* Small stash of WC pages
*/
- struct pagevec wc_stash;
+ struct pagestash wc_stash;
/**
* tmpfs instance used for shmem backed objects
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index c6aa761ca085..7048bfb282dc 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -375,27 +375,60 @@ static gen6_pte_t iris_pte_encode(dma_addr_t addr,
return pte;
}
+static void stash_init(struct pagestash *stash)
+{
+ pagevec_init(&stash->pvec);
+ spin_lock_init(&stash->lock);
+}
+
+static struct page *stash_get(struct pagestash *stash)
stash_get_page?
+{
+ struct page *page = NULL;
+
+ spin_lock(&stash->lock);
+ if (likely(stash->pvec.nr))
+ page = stash->pvec.pages[--stash->pvec.nr];
+ spin_unlock(&stash->lock);
+
+ return page;
+}
+
+static void stash_push(struct pagestash *stash, struct pagevec *pvec)
stash_append_pagevec?
+{
+ int nr;
+
+ spin_lock(&stash->lock);
+
+ nr = min_t(int, pvec->nr, pagevec_space(&stash->pvec));
+ memcpy(stash->pvec.pages + stash->pvec.nr,
+ pvec->pages + pvec->nr - nr,
+ sizeof(pvec->pages[0]) * nr);
+ stash->pvec.nr += nr;
+
+ spin_unlock(&stash->lock);
+
+ pvec->nr -= nr;
+}
+
static struct page *vm_alloc_page(struct i915_address_space *vm, gfp_t gfp)
{
- struct pagevec *pvec = &vm->free_pages;
- struct pagevec stash;
+ struct pagevec stack;
+ struct page *page;
if (I915_SELFTEST_ONLY(should_fail(&vm->fault_attr, 1)))
i915_gem_shrink_all(vm->i915);
- if (likely(pvec->nr))
- return pvec->pages[--pvec->nr];
+ page = stash_get(&vm->free_pages);
+ if (page)
+ return page;
if (!vm->pt_kmap_wc)
return alloc_page(gfp);
- /* A placeholder for a specific mutex to guard the WC stash */
- lockdep_assert_held(&vm->i915->drm.struct_mutex);
-
/* Look in our global stash of WC pages... */
- pvec = &vm->i915->mm.wc_stash;
- if (likely(pvec->nr))
- return pvec->pages[--pvec->nr];
+ page = stash_get(&vm->i915->mm.wc_stash);
+ if (page)
+ return page;
/*
* Otherwise batch allocate pages to amoritize cost of set_pages_wc.
@@ -405,7 +438,6 @@ static struct page *vm_alloc_page(struct i915_address_space *vm, gfp_t gfp)
* So we add our WB pages into a temporary pvec on the stack and merge
* them into the WC stash after all the allocations are complete.
*/
- pagevec_init(&stash);
Stack look uninitialized.
do {
struct page *page;
@@ -413,59 +445,67 @@ static struct page *vm_alloc_page(struct i915_address_space *vm, gfp_t gfp)
if (unlikely(!page))
break;
- stash.pages[stash.nr++] = page;
- } while (stash.nr < pagevec_space(pvec));
+ stack.pages[stack.nr++] = page;
+ } while (pagevec_space(&stack));
- if (stash.nr) {
- int nr = min_t(int, stash.nr, pagevec_space(pvec));
- struct page **pages = stash.pages + stash.nr - nr;
+ if (stack.nr && !set_pages_array_wc(stack.pages, stack.nr)) {
+ page = stack.pages[--stack.nr];
- if (nr && !set_pages_array_wc(pages, nr)) {
- memcpy(pvec->pages + pvec->nr,
- pages, sizeof(pages[0]) * nr);
- pvec->nr += nr;
- stash.nr -= nr;
- }
+ /* Merge spare WC pages to the global stash */
+ stash_push(&vm->i915->mm.wc_stash, &stack);
+
+ /* Push any surplus WC pages onto the local VM stash */
+ if (stack.nr)
+ stash_push(&vm->free_pages, &stack);
+ }
- pagevec_release(&stash);
+ /* Return unwanted leftovers */
+ if (unlikely(stack.nr)) {
+ WARN_ON_ONCE(set_pages_array_wb(stack.pages, stack.nr));
+ __pagevec_release(&stack);
Hmm.. I thought there can't be any. But in multi-threaded cases it can be.
}
- return likely(pvec->nr) ? pvec->pages[--pvec->nr] : NULL;
+ return page;
}
static void vm_free_pages_release(struct i915_address_space *vm,
- bool immediate)
+ unsigned int immediate)
Change the name at least if you cannot resist changing the semantics.
{
- struct pagevec *pvec = &vm->free_pages;
+ struct pagevec *pvec = &vm->free_pages.pvec;
+ struct pagevec stack;
+ lockdep_assert_held(&vm->free_pages.lock);
GEM_BUG_ON(!pagevec_count(pvec));
if (vm->pt_kmap_wc) {
- struct pagevec *stash = &vm->i915->mm.wc_stash;
-
- /* When we use WC, first fill up the global stash and then
+ /*
+ * When we use WC, first fill up the global stash and then
* only if full immediately free the overflow.
*/
+ stash_push(&vm->i915->mm.wc_stash, pvec);
- lockdep_assert_held(&vm->i915->drm.struct_mutex);
- if (pagevec_space(stash)) {
- do {
- stash->pages[stash->nr++] =
- pvec->pages[--pvec->nr];
- if (!pvec->nr)
- return;
- } while (pagevec_space(stash));
-
- /* As we have made some room in the VM's free_pages,
- * we can wait for it to fill again. Unless we are
- * inside i915_address_space_fini() and must
- * immediately release the pages!
- */
- if (!immediate)
- return;
- }
+ /*
+ * As we have made some room in the VM's free_pages,
+ * we can wait for it to fill again. Unless we are
+ * inside i915_address_space_fini() and must
+ * immediately release the pages!
+ */
+ if (pvec->nr <= immediate)
+ return;
+
+ /*
+ * We have to drop the lock to allow ourselves to sleep,
+ * so take a copy of the pvec and clear the stash for
+ * others to use it as we sleep.
+ */
+ stack = *pvec;
+ pagevec_init(pvec);
+ spin_unlock(&vm->free_pages.lock);
+ pvec = &stack;
set_pages_array_wb(pvec->pages, pvec->nr);
+
+ spin_lock(&vm->free_pages.lock);
}
__pagevec_release(pvec);
@@ -481,8 +521,10 @@ static void vm_free_page(struct i915_address_space *vm, struct page *page)
* unconditional might_sleep() for everybody.
*/
might_sleep();
- if (!pagevec_add(&vm->free_pages, page))
- vm_free_pages_release(vm, false);
+ spin_lock(&vm->free_pages.lock);
+ if (!pagevec_add(&vm->free_pages.pvec, page))
+ vm_free_pages_release(vm, PAGEVEC_SIZE - 1);
+ spin_unlock(&vm->free_pages.lock);
}
static int __setup_page_dma(struct i915_address_space *vm,
@@ -2112,18 +2154,22 @@ static void i915_address_space_init(struct i915_address_space *vm,
drm_mm_init(&vm->mm, 0, vm->total);
vm->mm.head_node.color = I915_COLOR_UNEVICTABLE;
+ stash_init(&vm->free_pages);
+
INIT_LIST_HEAD(&vm->active_list);
INIT_LIST_HEAD(&vm->inactive_list);
INIT_LIST_HEAD(&vm->unbound_list);
list_add_tail(&vm->global_link, &dev_priv->vm_list);
- pagevec_init(&vm->free_pages);
}
static void i915_address_space_fini(struct i915_address_space *vm)
{
- if (pagevec_count(&vm->free_pages))
- vm_free_pages_release(vm, true);
+ spin_lock(&vm->free_pages.lock);
+ if (pagevec_count(&vm->free_pages.pvec))
+ vm_free_pages_release(vm, 0);
+ GEM_BUG_ON(pagevec_count(&vm->free_pages.pvec));
+ spin_unlock(&vm->free_pages.lock);
drm_mm_takedown(&vm->mm);
list_del(&vm->global_link);
@@ -2918,7 +2964,7 @@ void i915_ggtt_cleanup_hw(struct drm_i915_private *dev_priv)
ggtt->vm.cleanup(&ggtt->vm);
- pvec = &dev_priv->mm.wc_stash;
+ pvec = &dev_priv->mm.wc_stash.pvec;
if (pvec->nr) {
set_pages_array_wb(pvec->pages, pvec->nr);
__pagevec_release(pvec);
@@ -3518,6 +3564,8 @@ int i915_ggtt_init_hw(struct drm_i915_private *dev_priv)
struct i915_ggtt *ggtt = &dev_priv->ggtt;
int ret;
+ stash_init(&dev_priv->mm.wc_stash);
+
INIT_LIST_HEAD(&dev_priv->vm_list);
/* Note that we use page colouring to enforce a guard page at the
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.h b/drivers/gpu/drm/i915/i915_gem_gtt.h
index 9a4824cae68d..9c2089c270f8 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.h
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.h
@@ -270,6 +270,11 @@ struct i915_vma_ops {
void (*clear_pages)(struct i915_vma *vma);
};
+struct pagestash {
+ spinlock_t lock;
+ struct pagevec pvec;
+};
+
struct i915_address_space {
struct drm_mm mm;
struct drm_i915_private *i915;
@@ -324,7 +329,7 @@ struct i915_address_space {
*/
struct list_head unbound_list;
- struct pagevec free_pages;
+ struct pagestash free_pages;
bool pt_kmap_wc;
/* FIXME: Need a more generic return type */
Regards,
Tvrtko
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