| Message ID | 20210204105638.1584-2-haokexin@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | net: Avoid the memory waste in some Ethernet drivers | expand |
On Thu, Feb 4, 2021 at 3:06 AM Kevin Hao <haokexin@gmail.com> wrote: > > In the current implementation of page_frag_alloc(), it doesn't have > any align guarantee for the returned buffer address. But for some > hardwares they do require the DMA buffer to be aligned correctly, > so we would have to use some workarounds like below if the buffers > allocated by the page_frag_alloc() are used by these hardwares for > DMA. > buf = page_frag_alloc(really_needed_size + align); > buf = PTR_ALIGN(buf, align); > > These codes seems ugly and would waste a lot of memories if the buffers > are used in a network driver for the TX/RX. So introduce > page_frag_alloc_align() to make sure that an aligned buffer address is > returned. > > Signed-off-by: Kevin Hao <haokexin@gmail.com> > Acked-by: Vlastimil Babka <vbabka@suse.cz> > --- > v3: Use align mask as suggested by Alexander. > > include/linux/gfp.h | 12 ++++++++++-- > mm/page_alloc.c | 8 +++++--- > 2 files changed, 15 insertions(+), 5 deletions(-) Looks good to me. Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
diff --git a/include/linux/gfp.h b/include/linux/gfp.h index 53caa9846854..52cd415b436c 100644 --- a/include/linux/gfp.h +++ b/include/linux/gfp.h @@ -583,8 +583,16 @@ extern void free_pages(unsigned long addr, unsigned int order); struct page_frag_cache; extern void __page_frag_cache_drain(struct page *page, unsigned int count); -extern void *page_frag_alloc(struct page_frag_cache *nc, - unsigned int fragsz, gfp_t gfp_mask); +extern void *page_frag_alloc_align(struct page_frag_cache *nc, + unsigned int fragsz, gfp_t gfp_mask, + unsigned int align_mask); + +static inline void *page_frag_alloc(struct page_frag_cache *nc, + unsigned int fragsz, gfp_t gfp_mask) +{ + return page_frag_alloc_align(nc, fragsz, gfp_mask, ~0u); +} + extern void page_frag_free(void *addr); #define __free_page(page) __free_pages((page), 0) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index ad3ed3ec4dd5..3583c6accd88 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -5137,8 +5137,9 @@ void __page_frag_cache_drain(struct page *page, unsigned int count) } EXPORT_SYMBOL(__page_frag_cache_drain); -void *page_frag_alloc(struct page_frag_cache *nc, - unsigned int fragsz, gfp_t gfp_mask) +void *page_frag_alloc_align(struct page_frag_cache *nc, + unsigned int fragsz, gfp_t gfp_mask, + unsigned int align_mask) { unsigned int size = PAGE_SIZE; struct page *page; @@ -5190,11 +5191,12 @@ void *page_frag_alloc(struct page_frag_cache *nc, } nc->pagecnt_bias--; + offset &= align_mask; nc->offset = offset; return nc->va + offset; } -EXPORT_SYMBOL(page_frag_alloc); +EXPORT_SYMBOL(page_frag_alloc_align); /* * Frees a page fragment allocated out of either a compound or order 0 page.
In the current implementation of page_frag_alloc(), it doesn't have any align guarantee for the returned buffer address. But for some hardwares they do require the DMA buffer to be aligned correctly, so we would have to use some workarounds like below if the buffers allocated by the page_frag_alloc() are used by these hardwares for DMA. buf = page_frag_alloc(really_needed_size + align); buf = PTR_ALIGN(buf, align); These codes seems ugly and would waste a lot of memories if the buffers are used in a network driver for the TX/RX. So introduce page_frag_alloc_align() to make sure that an aligned buffer address is returned. Signed-off-by: Kevin Hao <haokexin@gmail.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> --- v3: Use align mask as suggested by Alexander. include/linux/gfp.h | 12 ++++++++++-- mm/page_alloc.c | 8 +++++--- 2 files changed, 15 insertions(+), 5 deletions(-)