This patch provides infrastructure for deferring buffer frees.
This is a feature ION provided which when used with some form of a page pool, provides a nice performance boost in an allocation microbenchmark. The reason it helps is it allows the page-zeroing to be done out of the normal allocation/free path, and pushed off to a kthread.
As not all heaps will find this useful, its implemented as a optional helper library that heaps can utilize.
Cc: Daniel Vetter daniel@ffwll.ch Cc: Sumit Semwal sumit.semwal@linaro.org Cc: Liam Mark lmark@codeaurora.org Cc: Chris Goldsworthy cgoldswo@codeaurora.org Cc: Laura Abbott labbott@kernel.org Cc: Brian Starkey Brian.Starkey@arm.com Cc: Hridya Valsaraju hridya@google.com Cc: Suren Baghdasaryan surenb@google.com Cc: Sandeep Patil sspatil@google.com Cc: Daniel Mentz danielmentz@google.com Cc: Ørjan Eide orjan.eide@arm.com Cc: Robin Murphy robin.murphy@arm.com Cc: Ezequiel Garcia ezequiel@collabora.com Cc: Simon Ser contact@emersion.fr Cc: James Jones jajones@nvidia.com Cc: linux-media@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Signed-off-by: John Stultz john.stultz@linaro.org --- v2: * Fix sleep in atomic issue from using a mutex, by switching to a spinlock as Reported-by: kernel test robot oliver.sang@intel.com * Cleanup API to use a reason enum for clarity and add some documentation comments as suggested by Suren Baghdasaryan. --- drivers/dma-buf/heaps/Kconfig | 3 + drivers/dma-buf/heaps/Makefile | 1 + drivers/dma-buf/heaps/deferred-free-helper.c | 136 +++++++++++++++++++ drivers/dma-buf/heaps/deferred-free-helper.h | 55 ++++++++ 4 files changed, 195 insertions(+) create mode 100644 drivers/dma-buf/heaps/deferred-free-helper.c create mode 100644 drivers/dma-buf/heaps/deferred-free-helper.h
diff --git a/drivers/dma-buf/heaps/Kconfig b/drivers/dma-buf/heaps/Kconfig index a5eef06c4226..ecf65204f714 100644 --- a/drivers/dma-buf/heaps/Kconfig +++ b/drivers/dma-buf/heaps/Kconfig @@ -1,3 +1,6 @@ +config DMABUF_HEAPS_DEFERRED_FREE + bool + config DMABUF_HEAPS_SYSTEM bool "DMA-BUF System Heap" depends on DMABUF_HEAPS diff --git a/drivers/dma-buf/heaps/Makefile b/drivers/dma-buf/heaps/Makefile index 974467791032..4e7839875615 100644 --- a/drivers/dma-buf/heaps/Makefile +++ b/drivers/dma-buf/heaps/Makefile @@ -1,3 +1,4 @@ # SPDX-License-Identifier: GPL-2.0 +obj-$(CONFIG_DMABUF_HEAPS_DEFERRED_FREE) += deferred-free-helper.o obj-$(CONFIG_DMABUF_HEAPS_SYSTEM) += system_heap.o obj-$(CONFIG_DMABUF_HEAPS_CMA) += cma_heap.o diff --git a/drivers/dma-buf/heaps/deferred-free-helper.c b/drivers/dma-buf/heaps/deferred-free-helper.c new file mode 100644 index 000000000000..cf04148167a2 --- /dev/null +++ b/drivers/dma-buf/heaps/deferred-free-helper.c @@ -0,0 +1,136 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Deferred dmabuf freeing helper + * + * Copyright (C) 2020 Linaro, Ltd. + * + * Based on the ION page pool code + * Copyright (C) 2011 Google, Inc. + */ + +#include <linux/freezer.h> +#include <linux/list.h> +#include <linux/slab.h> +#include <linux/swap.h> +#include <linux/sched/signal.h> + +#include "deferred-free-helper.h" + +static LIST_HEAD(free_list); +static size_t list_size; +wait_queue_head_t freelist_waitqueue; +struct task_struct *freelist_task; +static DEFINE_SPINLOCK(free_list_lock); + +void deferred_free(struct deferred_freelist_item *item, + void (*free)(struct deferred_freelist_item*, + enum df_reason), + size_t size) +{ + unsigned long flags; + + INIT_LIST_HEAD(&item->list); + item->size = size; + item->free = free; + + spin_lock_irqsave(&free_list_lock, flags); + list_add(&item->list, &free_list); + list_size += size; + spin_unlock_irqrestore(&free_list_lock, flags); + wake_up(&freelist_waitqueue); +} + +static size_t free_one_item(enum df_reason reason) +{ + unsigned long flags; + size_t size = 0; + struct deferred_freelist_item *item; + + spin_lock_irqsave(&free_list_lock, flags); + if (list_empty(&free_list)) { + spin_unlock_irqrestore(&free_list_lock, flags); + return 0; + } + item = list_first_entry(&free_list, struct deferred_freelist_item, list); + list_del(&item->list); + size = item->size; + list_size -= size; + spin_unlock_irqrestore(&free_list_lock, flags); + + item->free(item, reason); + return size; +} + +static unsigned long get_freelist_size(void) +{ + unsigned long size; + unsigned long flags; + + spin_lock_irqsave(&free_list_lock, flags); + size = list_size; + spin_unlock_irqrestore(&free_list_lock, flags); + return size; +} + +static unsigned long freelist_shrink_count(struct shrinker *shrinker, + struct shrink_control *sc) +{ + return get_freelist_size(); +} + +static unsigned long freelist_shrink_scan(struct shrinker *shrinker, + struct shrink_control *sc) +{ + int total_freed = 0; + + if (sc->nr_to_scan == 0) + return 0; + + while (total_freed < sc->nr_to_scan) { + int freed = free_one_item(DF_UNDER_PRESSURE); + + if (!freed) + break; + + total_freed += freed; + } + + return total_freed; +} + +static struct shrinker freelist_shrinker = { + .count_objects = freelist_shrink_count, + .scan_objects = freelist_shrink_scan, + .seeks = DEFAULT_SEEKS, + .batch = 0, +}; + +static int deferred_free_thread(void *data) +{ + while (true) { + wait_event_freezable(freelist_waitqueue, + get_freelist_size() > 0); + + free_one_item(DF_NORMAL); + } + + return 0; +} + +static int deferred_freelist_init(void) +{ + list_size = 0; + + init_waitqueue_head(&freelist_waitqueue); + freelist_task = kthread_run(deferred_free_thread, NULL, + "%s", "dmabuf-deferred-free-worker"); + if (IS_ERR(freelist_task)) { + pr_err("%s: creating thread for deferred free failed\n", + __func__); + return -1; + } + sched_set_normal(freelist_task, 19); + + return register_shrinker(&freelist_shrinker); +} +device_initcall(deferred_freelist_init); diff --git a/drivers/dma-buf/heaps/deferred-free-helper.h b/drivers/dma-buf/heaps/deferred-free-helper.h new file mode 100644 index 000000000000..2c43dd5a3eda --- /dev/null +++ b/drivers/dma-buf/heaps/deferred-free-helper.h @@ -0,0 +1,55 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +#ifndef DEFERRED_FREE_HELPER_H +#define DEFERRED_FREE_HELPER_H + +/** + * df_reason - enum for reason why item was freed + * + * This provides a reason for why the free funciton was called + * on the item. This is useful when deferred_free is used in + * combination with a pagepool, so under pressure the page can + * be immediately freed. + * + * DF_NORMAL: Normal deferred free + * + * DF_UNDER_PRESSURE: Free was called because the system + * is under memory pressure. Usually + * from a shrinker. Avoid allocating + * memory in the free call, as it may + * fail. + */ +enum df_reason { + DF_NORMAL, + DF_UNDER_PRESSURE, +}; + +/** + * deferred_freelist_item - item structure for deferred freelist + * + * This is to be added to the structure for whatever you want to + * defer freeing on. + * + * @size: size of the item to be freed + * @free: function pointer to be called when freeing the item + * @list: list entry for the deferred list + */ +struct deferred_freelist_item { + size_t size; + void (*free)(struct deferred_freelist_item *i, + enum df_reason reason); + struct list_head list; +}; + +/** + * deferred_free - call to add item to the deferred free list + * + * @item: Pointer to deferred_freelist_item field of a structure + * @free: Function pointer to the free call + * @size: Size of the item to be freed + */ +void deferred_free(struct deferred_freelist_item *item, + void (*free)(struct deferred_freelist_item *i, + enum df_reason reason), + size_t size); +#endif
Reuse/abuse the pagepool code from the network code to speed up allocation performance.
This is similar to the ION pagepool usage, but tries to utilize generic code instead of a custom implementation.
Cc: Daniel Vetter daniel@ffwll.ch Cc: Sumit Semwal sumit.semwal@linaro.org Cc: Liam Mark lmark@codeaurora.org Cc: Chris Goldsworthy cgoldswo@codeaurora.org Cc: Laura Abbott labbott@kernel.org Cc: Brian Starkey Brian.Starkey@arm.com Cc: Hridya Valsaraju hridya@google.com Cc: Suren Baghdasaryan surenb@google.com Cc: Sandeep Patil sspatil@google.com Cc: Daniel Mentz danielmentz@google.com Cc: Ørjan Eide orjan.eide@arm.com Cc: Robin Murphy robin.murphy@arm.com Cc: Ezequiel Garcia ezequiel@collabora.com Cc: Simon Ser contact@emersion.fr Cc: James Jones jajones@nvidia.com Cc: linux-media@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Signed-off-by: John Stultz john.stultz@linaro.org --- v2: * Fix build issue caused by selecting PAGE_POOL w/o NET as Reported-by: kernel test robot lkp@intel.com --- drivers/dma-buf/heaps/Kconfig | 2 + drivers/dma-buf/heaps/system_heap.c | 68 +++++++++++++++++++++++++++-- 2 files changed, 66 insertions(+), 4 deletions(-)
diff --git a/drivers/dma-buf/heaps/Kconfig b/drivers/dma-buf/heaps/Kconfig index ecf65204f714..748e840e6edd 100644 --- a/drivers/dma-buf/heaps/Kconfig +++ b/drivers/dma-buf/heaps/Kconfig @@ -4,6 +4,8 @@ config DMABUF_HEAPS_DEFERRED_FREE config DMABUF_HEAPS_SYSTEM bool "DMA-BUF System Heap" depends on DMABUF_HEAPS + select NET + select PAGE_POOL help Choose this option to enable the system dmabuf heap. The system heap is backed by pages from the buddy allocator. If in doubt, say Y. diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c index 17e0e9a68baf..885e30894b77 100644 --- a/drivers/dma-buf/heaps/system_heap.c +++ b/drivers/dma-buf/heaps/system_heap.c @@ -20,6 +20,7 @@ #include <linux/scatterlist.h> #include <linux/slab.h> #include <linux/vmalloc.h> +#include <net/page_pool.h>
static struct dma_heap *sys_heap;
@@ -53,6 +54,7 @@ static gfp_t order_flags[] = {HIGH_ORDER_GFP, LOW_ORDER_GFP, LOW_ORDER_GFP}; */ static const unsigned int orders[] = {8, 4, 0}; #define NUM_ORDERS ARRAY_SIZE(orders) +struct page_pool *pools[NUM_ORDERS];
static struct sg_table *dup_sg_table(struct sg_table *table) { @@ -281,18 +283,59 @@ static void system_heap_vunmap(struct dma_buf *dmabuf, struct dma_buf_map *map) dma_buf_map_clear(map); }
+static int system_heap_clear_pages(struct page **pages, int num, pgprot_t pgprot) +{ + void *addr = vmap(pages, num, VM_MAP, pgprot); + + if (!addr) + return -ENOMEM; + memset(addr, 0, PAGE_SIZE * num); + vunmap(addr); + return 0; +} + +static int system_heap_zero_buffer(struct system_heap_buffer *buffer) +{ + struct sg_table *sgt = &buffer->sg_table; + struct sg_page_iter piter; + struct page *pages[32]; + int p = 0; + int ret = 0; + + for_each_sgtable_page(sgt, &piter, 0) { + pages[p++] = sg_page_iter_page(&piter); + if (p == ARRAY_SIZE(pages)) { + ret = system_heap_clear_pages(pages, p, PAGE_KERNEL); + if (ret) + return ret; + p = 0; + } + } + if (p) + ret = system_heap_clear_pages(pages, p, PAGE_KERNEL); + + return ret; +} + static void system_heap_dma_buf_release(struct dma_buf *dmabuf) { struct system_heap_buffer *buffer = dmabuf->priv; struct sg_table *table; struct scatterlist *sg; - int i; + int i, j; + + /* Zero the buffer pages before adding back to the pool */ + system_heap_zero_buffer(buffer);
table = &buffer->sg_table; for_each_sg(table->sgl, sg, table->nents, i) { struct page *page = sg_page(sg);
- __free_pages(page, compound_order(page)); + for (j = 0; j < NUM_ORDERS; j++) { + if (compound_order(page) == orders[j]) + break; + } + page_pool_put_full_page(pools[j], page, false); } sg_free_table(table); kfree(buffer); @@ -322,8 +365,7 @@ static struct page *alloc_largest_available(unsigned long size, continue; if (max_order < orders[i]) continue; - - page = alloc_pages(order_flags[i], orders[i]); + page = page_pool_alloc_pages(pools[i], order_flags[i]); if (!page) continue; return page; @@ -428,6 +470,24 @@ static const struct dma_heap_ops system_heap_ops = { static int system_heap_create(void) { struct dma_heap_export_info exp_info; + int i; + + for (i = 0; i < NUM_ORDERS; i++) { + struct page_pool_params pp; + + memset(&pp, 0, sizeof(pp)); + pp.order = orders[i]; + pools[i] = page_pool_create(&pp); + + if (IS_ERR(pools[i])) { + int j; + + pr_err("%s: page pool creation failed!\n", __func__); + for (j = 0; j < i; j++) + page_pool_destroy(pools[j]); + return PTR_ERR(pools[i]); + } + }
exp_info.name = "system"; exp_info.ops = &system_heap_ops;
On Fri, Jan 22, 2021 at 7:47 PM John Stultz john.stultz@linaro.org wrote:
+static int system_heap_clear_pages(struct page **pages, int num, pgprot_t pgprot) +{
void *addr = vmap(pages, num, VM_MAP, pgprot);if (!addr)return -ENOMEM;memset(addr, 0, PAGE_SIZE * num);vunmap(addr);return 0;+}
I thought that vmap/vunmap are expensive, and I am wondering if there's a faster way that avoids vmap.
How about lifting this code from lib/iov_iter.c static void memzero_page(struct page *page, size_t offset, size_t len) { char *addr = kmap_atomic(page); memset(addr + offset, 0, len); kunmap_atomic(addr); }
Or what about lifting that code from the old ion_cma_heap.c
if (PageHighMem(pages)) { unsigned long nr_clear_pages = nr_pages; struct page *page = pages;
while (nr_clear_pages > 0) { void *vaddr = kmap_atomic(page);
memset(vaddr, 0, PAGE_SIZE); kunmap_atomic(vaddr); page++; nr_clear_pages--; } } else { memset(page_address(pages), 0, size); }
On Wed, Jan 27, 2021 at 12:21 PM Daniel Mentz danielmentz@google.com wrote:
On Fri, Jan 22, 2021 at 7:47 PM John Stultz john.stultz@linaro.org wrote:
+static int system_heap_clear_pages(struct page **pages, int num, pgprot_t pgprot) +{
void *addr = vmap(pages, num, VM_MAP, pgprot);if (!addr)return -ENOMEM;memset(addr, 0, PAGE_SIZE * num);vunmap(addr);return 0;+}
I thought that vmap/vunmap are expensive, and I am wondering if there's a faster way that avoids vmap.
How about lifting this code from lib/iov_iter.c static void memzero_page(struct page *page, size_t offset, size_t len) { char *addr = kmap_atomic(page); memset(addr + offset, 0, len); kunmap_atomic(addr); }
Or what about lifting that code from the old ion_cma_heap.c
if (PageHighMem(pages)) { unsigned long nr_clear_pages = nr_pages; struct page *page = pages;
while (nr_clear_pages > 0) { void *vaddr = kmap_atomic(page); memset(vaddr, 0, PAGE_SIZE); kunmap_atomic(vaddr); page++; nr_clear_pages--; }} else { memset(page_address(pages), 0, size); }
Though, this last memset only works since CMA is contiguous, so it probably needs to always do the kmap_atomic for each page, right?
I'm still a little worried if this is right, as the current implementation with the vmap comes from the old ion_heap_sglist_zero logic, which similarly tries to batch the vmaps 32 pages at at time, but I'll give it a try.
thanks -john
On Wed, Jan 27, 2021 at 9:10 PM John Stultz john.stultz@linaro.org wrote:
On Wed, Jan 27, 2021 at 12:21 PM Daniel Mentz danielmentz@google.com wrote:
On Fri, Jan 22, 2021 at 7:47 PM John Stultz john.stultz@linaro.org wrote:
+static int system_heap_clear_pages(struct page **pages, int num, pgprot_t pgprot) +{
void *addr = vmap(pages, num, VM_MAP, pgprot);if (!addr)return -ENOMEM;memset(addr, 0, PAGE_SIZE * num);vunmap(addr);return 0;+}
I thought that vmap/vunmap are expensive, and I am wondering if there's a faster way that avoids vmap.
How about lifting this code from lib/iov_iter.c static void memzero_page(struct page *page, size_t offset, size_t len) { char *addr = kmap_atomic(page); memset(addr + offset, 0, len); kunmap_atomic(addr); }
Or what about lifting that code from the old ion_cma_heap.c
if (PageHighMem(pages)) { unsigned long nr_clear_pages = nr_pages; struct page *page = pages;
while (nr_clear_pages > 0) { void *vaddr = kmap_atomic(page); memset(vaddr, 0, PAGE_SIZE); kunmap_atomic(vaddr); page++; nr_clear_pages--; }} else { memset(page_address(pages), 0, size); }
Though, this last memset only works since CMA is contiguous, so it probably needs to always do the kmap_atomic for each page, right?
Yeah, but with the system heap page pool, some of these pages might be 64KB or 1MB large. kmap_atomic(page) just maps to page_address(page) in most cases. I think iterating over all pages individually in this manner might still be faster than using vmap.
I'm still a little worried if this is right, as the current implementation with the vmap comes from the old ion_heap_sglist_zero logic, which similarly tries to batch the vmaps 32 pages at at time, but I'll give it a try.
Utilize the deferred free helper library in the system heap.
This provides a nice performance bump and puts the system heap performance on par with ION.
Cc: Daniel Vetter daniel@ffwll.ch Cc: Sumit Semwal sumit.semwal@linaro.org Cc: Liam Mark lmark@codeaurora.org Cc: Chris Goldsworthy cgoldswo@codeaurora.org Cc: Laura Abbott labbott@kernel.org Cc: Brian Starkey Brian.Starkey@arm.com Cc: Hridya Valsaraju hridya@google.com Cc: Suren Baghdasaryan surenb@google.com Cc: Sandeep Patil sspatil@google.com Cc: Daniel Mentz danielmentz@google.com Cc: Ørjan Eide orjan.eide@arm.com Cc: Robin Murphy robin.murphy@arm.com Cc: Ezequiel Garcia ezequiel@collabora.com Cc: Simon Ser contact@emersion.fr Cc: James Jones jajones@nvidia.com Cc: linux-media@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Signed-off-by: John Stultz john.stultz@linaro.org --- v2: * Rework deferred-free api to use reason enum as suggested by Suren Baghdasaryan --- drivers/dma-buf/heaps/Kconfig | 1 + drivers/dma-buf/heaps/system_heap.c | 32 ++++++++++++++++++++++------- 2 files changed, 26 insertions(+), 7 deletions(-)
diff --git a/drivers/dma-buf/heaps/Kconfig b/drivers/dma-buf/heaps/Kconfig index 748e840e6edd..3f4d7b949301 100644 --- a/drivers/dma-buf/heaps/Kconfig +++ b/drivers/dma-buf/heaps/Kconfig @@ -6,6 +6,7 @@ config DMABUF_HEAPS_SYSTEM depends on DMABUF_HEAPS select NET select PAGE_POOL + select DMABUF_HEAPS_DEFERRED_FREE help Choose this option to enable the system dmabuf heap. The system heap is backed by pages from the buddy allocator. If in doubt, say Y. diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c index 885e30894b77..747fa2250e84 100644 --- a/drivers/dma-buf/heaps/system_heap.c +++ b/drivers/dma-buf/heaps/system_heap.c @@ -22,6 +22,8 @@ #include <linux/vmalloc.h> #include <net/page_pool.h>
+#include "deferred-free-helper.h" + static struct dma_heap *sys_heap;
struct system_heap_buffer { @@ -32,6 +34,7 @@ struct system_heap_buffer { struct sg_table sg_table; int vmap_cnt; void *vaddr; + struct deferred_freelist_item deferred_free; };
struct dma_heap_attachment { @@ -317,30 +320,45 @@ static int system_heap_zero_buffer(struct system_heap_buffer *buffer) return ret; }
-static void system_heap_dma_buf_release(struct dma_buf *dmabuf) +static void system_heap_buf_free(struct deferred_freelist_item *item, + enum df_reason reason) { - struct system_heap_buffer *buffer = dmabuf->priv; + struct system_heap_buffer *buffer; struct sg_table *table; struct scatterlist *sg; int i, j;
+ buffer = container_of(item, struct system_heap_buffer, deferred_free); /* Zero the buffer pages before adding back to the pool */ - system_heap_zero_buffer(buffer); + if (reason == DF_NORMAL) + if (system_heap_zero_buffer(buffer)) + reason = DF_UNDER_PRESSURE; // On failure, just free
table = &buffer->sg_table; for_each_sg(table->sgl, sg, table->nents, i) { struct page *page = sg_page(sg);
- for (j = 0; j < NUM_ORDERS; j++) { - if (compound_order(page) == orders[j]) - break; + if (reason == DF_UNDER_PRESSURE) { + __free_pages(page, compound_order(page)); + } else { + for (j = 0; j < NUM_ORDERS; j++) { + if (compound_order(page) == orders[j]) + break; + } + page_pool_put_full_page(pools[j], page, false); } - page_pool_put_full_page(pools[j], page, false); } sg_free_table(table); kfree(buffer); }
+static void system_heap_dma_buf_release(struct dma_buf *dmabuf) +{ + struct system_heap_buffer *buffer = dmabuf->priv; + + deferred_free(&buffer->deferred_free, system_heap_buf_free, buffer->len); +} + static const struct dma_buf_ops system_heap_buf_ops = { .attach = system_heap_attach, .detach = system_heap_detach,
dri-devel@lists.freedesktop.org
-
Daniel Mentz -
John Stultz