| Message ID | 20231013064827.61135-1-linyunsheng@huawei.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | introduce page_pool_alloc() related API | expand |
On Fri, 13 Oct 2023 14:48:20 +0800 Yunsheng Lin wrote: > v5 RFC: Add a new page_pool_cache_alloc() API, and other minor > change as discussed in v4. As there seems to be three > comsumers that might be made use of the new API, so > repost it as RFC and CC the relevant authors to see > if the new API fits their need. I have looked thru the v4 discussion (admittedly it was pretty huge). I can't find where the "cache" API was suggested. And I can't figure out now what the "cache" in the name is referring to. Looks like these are just convenience wrappers which return VA instead of struct page..
Hello: This series was applied to netdev/net-next.git (main) by Jakub Kicinski <kuba@kernel.org>: On Fri, 13 Oct 2023 14:48:20 +0800 you wrote: > In [1] & [2] & [3], there are usecases for veth and virtio_net > to use frag support in page pool to reduce memory usage, and it > may request different frag size depending on the head/tail > room space for xdp_frame/shinfo and mtu/packet size. When the > requested frag size is large enough that a single page can not > be split into more than one frag, using frag support only have > performance penalty because of the extra frag count handling > for frag support. > > [...] Here is the summary with links: - [net-next,v11,1/6] page_pool: fragment API support for 32-bit arch with 64-bit DMA https://git.kernel.org/netdev/net-next/c/90de47f020db - [net-next,v11,2/6] page_pool: unify frag_count handling in page_pool_is_last_frag() (no matching commit) - [net-next,v11,3/6] page_pool: remove PP_FLAG_PAGE_FRAG (no matching commit) - [net-next,v11,4/6] page_pool: introduce page_pool[_cache]_alloc() API (no matching commit) - [net-next,v11,5/6] page_pool: update document about fragment API (no matching commit) - [net-next,v11,6/6] net: veth: use newly added page pool API for veth with xdp (no matching commit) You are awesome, thank you!
On 2023/10/17 9:27, Jakub Kicinski wrote: > On Fri, 13 Oct 2023 14:48:20 +0800 Yunsheng Lin wrote: >> v5 RFC: Add a new page_pool_cache_alloc() API, and other minor >> change as discussed in v4. As there seems to be three >> comsumers that might be made use of the new API, so >> repost it as RFC and CC the relevant authors to see >> if the new API fits their need. > > I have looked thru the v4 discussion (admittedly it was pretty huge). > I can't find where the "cache" API was suggested. Actually, the discussion happened in V3 as both of discussions in V3 and V4 seems to be happening concurrently: https://lore.kernel.org/all/f8ce176f-f975-af11-641c-b56c53a8066a@redhat.com/ > And I can't figure out now what the "cache" in the name is referring to. > Looks like these are just convenience wrappers which return VA instead > of struct page.. Yes, it is corresponding to some API like napi_alloc_frag() returning va instead of 'struct page' mentioned in patch 5. Anyway, naming is hard, any suggestion for a better naming is always welcomed:) > . >
On Tue, 17 Oct 2023 15:56:48 +0800 Yunsheng Lin wrote: > > And I can't figure out now what the "cache" in the name is referring to. > > Looks like these are just convenience wrappers which return VA instead > > of struct page.. > > Yes, it is corresponding to some API like napi_alloc_frag() returning va > instead of 'struct page' mentioned in patch 5. > > Anyway, naming is hard, any suggestion for a better naming is always > welcomed:) I'd just throw a _va (for virtual address) at the end. And not really mention it in the documentation. Plus the kdoc of the function should say that this is just a thin wrapper around other page pool APIs, and it's safe to mix it with other page pool APIs?
On Tue, 17 Oct 2023 08:13:03 -0700 Jakub Kicinski wrote:
> I'd just throw a _va (for virtual address) at the end
To be clear I mean:
page_pool_alloc_va()
page_pool_dev_alloc_va()
page_pool_free_va()
On 2023/10/17 23:13, Jakub Kicinski wrote: > On Tue, 17 Oct 2023 15:56:48 +0800 Yunsheng Lin wrote: >>> And I can't figure out now what the "cache" in the name is referring to. >>> Looks like these are just convenience wrappers which return VA instead >>> of struct page.. >> >> Yes, it is corresponding to some API like napi_alloc_frag() returning va >> instead of 'struct page' mentioned in patch 5. >> >> Anyway, naming is hard, any suggestion for a better naming is always >> welcomed:) > > I'd just throw a _va (for virtual address) at the end. And not really _va seems fine:) > mention it in the documentation. Plus the kdoc of the function should > say that this is just a thin wrapper around other page pool APIs, and > it's safe to mix it with other page pool APIs? I am not sure I understand what do 'safe' and 'mix' mean here. For 'safe' part, I suppose you mean if there is a va accociated with a 'struct page' without calling some API like kmap()? For that, I suppose it is safe when the driver is calling page_pool API without the __GFP_HIGHMEM flag. Maybe we should mention that in the kdoc and give a warning if page_pool_*alloc_va() is called with the __GFP_HIGHMEM flag? For the 'mix', I suppose you mean the below: 1. Allocate a page with the page_pool_*alloc_va() API and free a page with page_pool_free() API. 2. Allocate a page with the page_pool_*alloc() API and free a page with page_pool_free_va() API. For 1, it seems it is ok as some virt_to_head_page() and page_address() call between va and 'struct page' does not seem to change anything if we have enforce page_pool_*alloc_va() to be called without the __GFP_HIGHMEM flag. For 2, If the va is returned from page_address() which the allocation API is called without __GFP_HIGHMEM flag. If not, the va is from kmap*()? which means we may be calling page_pool_free_va() before kunmap*()? Is that possible? > . >
On Wed, 18 Oct 2023 19:47:16 +0800 Yunsheng Lin wrote: > > mention it in the documentation. Plus the kdoc of the function should > > say that this is just a thin wrapper around other page pool APIs, and > > it's safe to mix it with other page pool APIs? > > I am not sure I understand what do 'safe' and 'mix' mean here. > > For 'safe' part, I suppose you mean if there is a va accociated with > a 'struct page' without calling some API like kmap()? For that, I suppose > it is safe when the driver is calling page_pool API without the > __GFP_HIGHMEM flag. Maybe we should mention that in the kdoc and give a > warning if page_pool_*alloc_va() is called with the __GFP_HIGHMEM flag? Sounds good. Warning wrapped in #if CONFIG_DEBUG_NET perhaps? > For the 'mix', I suppose you mean the below: > 1. Allocate a page with the page_pool_*alloc_va() API and free a page with > page_pool_free() API. > 2. Allocate a page with the page_pool_*alloc() API and free a page with > page_pool_free_va() API. > > For 1, it seems it is ok as some virt_to_head_page() and page_address() call > between va and 'struct page' does not seem to change anything if we have > enforce page_pool_*alloc_va() to be called without the __GFP_HIGHMEM flag. > > For 2, If the va is returned from page_address() which the allocation API is > called without __GFP_HIGHMEM flag. If not, the va is from kmap*()? which means > we may be calling page_pool_free_va() before kunmap*()? Is that possible? Right, if someone passes kmap()'ed address they are trying quite hard to break their own driver. Technically possible but I wouldn't worry. I just mean that in the common case of non-HIGHMEM page, calling page_pool_free_va() with the address returned by page_address() is perfectly legal.
On 2023/10/18 23:35, Jakub Kicinski wrote: > On Wed, 18 Oct 2023 19:47:16 +0800 Yunsheng Lin wrote: >>> mention it in the documentation. Plus the kdoc of the function should >>> say that this is just a thin wrapper around other page pool APIs, and >>> it's safe to mix it with other page pool APIs? >> >> I am not sure I understand what do 'safe' and 'mix' mean here. >> >> For 'safe' part, I suppose you mean if there is a va accociated with >> a 'struct page' without calling some API like kmap()? For that, I suppose >> it is safe when the driver is calling page_pool API without the >> __GFP_HIGHMEM flag. Maybe we should mention that in the kdoc and give a >> warning if page_pool_*alloc_va() is called with the __GFP_HIGHMEM flag? > > Sounds good. Warning wrapped in #if CONFIG_DEBUG_NET perhaps? How about something like __get_free_pages() does with gfp flags? https://elixir.free-electrons.com/linux/v6.4-rc6/source/mm/page_alloc.c#L4818 how about something like below on top of this patchset: diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h index 7550beeacf3d..61cee55606c0 100644 --- a/include/net/page_pool/helpers.h +++ b/include/net/page_pool/helpers.h @@ -167,13 +167,13 @@ static inline struct page *page_pool_dev_alloc(struct page_pool *pool, return page_pool_alloc(pool, offset, size, gfp); } -static inline void *page_pool_cache_alloc(struct page_pool *pool, - unsigned int *size, gfp_t gfp) +static inline void *page_pool_alloc_va(struct page_pool *pool, + unsigned int *size, gfp_t gfp) { unsigned int offset; struct page *page; - page = page_pool_alloc(pool, &offset, size, gfp); + page = page_pool_alloc(pool, &offset, size, gfp & ~__GFP_HIGHMEM); if (unlikely(!page)) return NULL; @@ -181,21 +181,22 @@ static inline void *page_pool_cache_alloc(struct page_pool *pool, } /** - * page_pool_dev_cache_alloc() - allocate a cache. + * page_pool_dev_alloc_va() - allocate a page or a page fragment. * @pool: pool from which to allocate * @size: in as the requested size, out as the allocated size * - * Get a cache from the page allocator or page_pool caches. + * This is just a thin wrapper around the page_pool_alloc() API, and + * it returns va of the allocated page or page fragment. * * Return: - * Return the addr for the allocated cache, otherwise return NULL. + * Return the va for the allocated page or page fragment, otherwise return NULL. */ -static inline void *page_pool_dev_cache_alloc(struct page_pool *pool, - unsigned int *size) +static inline void *page_pool_dev_alloc_va(struct page_pool *pool, + unsigned int *size) { gfp_t gfp = (GFP_ATOMIC | __GFP_NOWARN); - return page_pool_cache_alloc(pool, size, gfp); + return page_pool_alloc_va(pool, size, gfp); } /** @@ -338,17 +339,17 @@ static inline void page_pool_recycle_direct(struct page_pool *pool, (sizeof(dma_addr_t) > sizeof(unsigned long)) /** - * page_pool_cache_free() - free a cache into the page_pool - * @pool: pool from which cache was allocated - * @data: addr of cache to be free + * page_pool_free_va() - free a va into the page_pool + * @pool: pool from which va was allocated + * @va: va to be free * @allow_direct: freed by the consumer, allow lockless caching * * Free a cache allocated from page_pool_dev_cache_alloc(). */ -static inline void page_pool_cache_free(struct page_pool *pool, void *data, - bool allow_direct) +static inline void page_pool_free_va(struct page_pool *pool, void *va, + bool allow_direct) { - page_pool_put_page(pool, virt_to_head_page(data), -1, allow_direct); + page_pool_put_page(pool, virt_to_head_page(va), -1, allow_direct); }
On Thu, 19 Oct 2023 21:22:07 +0800 Yunsheng Lin wrote: > > Sounds good. Warning wrapped in #if CONFIG_DEBUG_NET perhaps? > > How about something like __get_free_pages() does with gfp flags? > https://elixir.free-electrons.com/linux/v6.4-rc6/source/mm/page_alloc.c#L4818 Fine by me!
In [1] & [2] & [3], there are usecases for veth and virtio_net to use frag support in page pool to reduce memory usage, and it may request different frag size depending on the head/tail room space for xdp_frame/shinfo and mtu/packet size. When the requested frag size is large enough that a single page can not be split into more than one frag, using frag support only have performance penalty because of the extra frag count handling for frag support. So this patchset provides a page pool API for the driver to allocate memory with least memory utilization and performance penalty when it doesn't know the size of memory it need beforehand. 1. https://patchwork.kernel.org/project/netdevbpf/patch/d3ae6bd3537fbce379382ac6a42f67e22f27ece2.1683896626.git.lorenzo@kernel.org/ 2. https://patchwork.kernel.org/project/netdevbpf/patch/20230526054621.18371-3-liangchen.linux@gmail.com/ 3. https://github.com/alobakin/linux/tree/iavf-pp-frag V11: Repost based on the latest net-next branch and collect Tested-by Tag from Alexander. V10: Use fragment instead of frag in English docs. Remove PP_FLAG_PAGE_FRAG usage in idpf driver. V9: Update some performance info in patch 2. V8: Store the dma addr on a shifted u32 instead of using dma_addr_t explicitly for 32-bit arch with 64-bit DMA. Update document according to discussion in v7. V7: Fix a compile error, a few typo and use kernel-doc syntax. V6: Add a PP_FLAG_PAGE_SPLIT_IN_DRIVER flag to fail the page_pool creation for 32-bit arch with 64-bit DMA when driver tries to do the page splitting itself, adjust the requested size to include head/tail room in veth, and rebased on the latest next-net. v5 RFC: Add a new page_pool_cache_alloc() API, and other minor change as discussed in v4. As there seems to be three comsumers that might be made use of the new API, so repost it as RFC and CC the relevant authors to see if the new API fits their need. V4. Fix a typo and add a patch to update document about frag API, PAGE_POOL_DMA_USE_PP_FRAG_COUNT is not renamed yet as we may need a different thread to discuss that. V3: Incorporate changes from the disscusion with Alexander, mostly the inline wraper, PAGE_POOL_DMA_USE_PP_FRAG_COUNT change split to separate patch and comment change. V2: Add patch to remove PP_FLAG_PAGE_FRAG flags and mention virtio_net usecase in the cover letter. V1: Drop RFC tag and page_pool_frag patch. Yunsheng Lin (6): page_pool: fragment API support for 32-bit arch with 64-bit DMA page_pool: unify frag_count handling in page_pool_is_last_frag() page_pool: remove PP_FLAG_PAGE_FRAG page_pool: introduce page_pool[_cache]_alloc() API page_pool: update document about fragment API net: veth: use newly added page pool API for veth with xdp Documentation/networking/page_pool.rst | 4 +- drivers/net/ethernet/broadcom/bnxt/bnxt.c | 2 - .../net/ethernet/hisilicon/hns3/hns3_enet.c | 3 +- drivers/net/ethernet/intel/idpf/idpf_txrx.c | 3 - .../marvell/octeontx2/nic/otx2_common.c | 2 +- .../net/ethernet/mellanox/mlx5/core/en_main.c | 2 +- drivers/net/veth.c | 25 +- drivers/net/wireless/mediatek/mt76/mac80211.c | 2 +- include/linux/mm_types.h | 13 +- include/net/page_pool/helpers.h | 231 +++++++++++++++--- include/net/page_pool/types.h | 6 +- net/core/page_pool.c | 31 ++- net/core/skbuff.c | 2 +- 13 files changed, 243 insertions(+), 83 deletions(-)