From nobody Sun Dec 14 13:56:59 2025 Received: from mail-pl1-f169.google.com (mail-pl1-f169.google.com [209.85.214.169]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E268C33F3 for ; Tue, 21 Oct 2025 04:20:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.169 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761020449; cv=none; b=bSATB89Ukr2IAeTRkYe8ryPF6htqNG88cUQ7rm7VLlvK3QFZ/p6KTrAOQBGa0NCV+azU7QDS+1pUlTiH+xDaGrX5/5YLxXqlI01RLTxhbx2tKBlnfiLc8CGC10OgAqbtZ56lXEMnghVoc/uLNt/RcbuvbSXIshMRl9HkmTPKdcY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761020449; c=relaxed/simple; bh=54IdDzBB1F8JHTZwkrbY0+nkyH6X9WaOpkcrR10tcBY=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=KkX7BRT01EBFSP8n7wtUnn7dj74KcK94wUvqez+YG3kvdhAKhCB4osnwv66+CtZCVWFfr1JpzbctdvbL2CAaSuGmi8HmEbBRpQs2aWvBzXuudHEFQiSjx19kTCR5WUGDWpBf9Hss5M+aH5ALg+Dyyc5DhJ6abT+MLT4sXzOW6Tc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=aNrO+JFQ; arc=none smtp.client-ip=209.85.214.169 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="aNrO+JFQ" Received: by mail-pl1-f169.google.com with SMTP id d9443c01a7336-26a0a694ea8so37099275ad.3 for ; Mon, 20 Oct 2025 21:20:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1761020447; x=1761625247; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=SRLdP4GmC8TAaehpYwLWmY0fXaXzRogSZM1ApFlMens=; b=aNrO+JFQJwug/LAS2SNfun1J0Oo0tsKhiEwpr+O2q/EBir7fDU95d6XxUiGFMDFKpd JlOeEWFYBfHtjDCp/vNaXAVgV8m8E9iJUrU382p2A19e98/SpIVZHusN/TT5m3qmmc7p yoPnq6V6yZr0aWQi4B/st3B4nRlmIVrIdo5uEp1mdZB0+b5pBDdzffOoM3/gvje9btHV snjMvoM0vYUZ6r2dK9GUyZk0zYGwFvaeWCYuDLBxoi726pfK7r0ZAsohijVKdhGhQtDM xTrTY5Wf8Fb94VThqLOYgNZkI4atjQfnv+Qc63bkexzNUHxVkkQ+wyKbSMD/SNCC2MOZ ethA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1761020447; x=1761625247; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=SRLdP4GmC8TAaehpYwLWmY0fXaXzRogSZM1ApFlMens=; b=cJP6NcPACviuKqaWcJ1OLCnHn9CrIsqcLNxsQURgNU9WS8DblT/CZoAgZLL3hFlNoJ 1s3U+RKTc1lKn+3o+N4noDOZwkl3Rc+ySuFhZhz5+jG5usLKHk2KlxwGLJgP3dqSJSER 94RgrSn5UKjFroeICqW8U3bmnv4W2PhDREjVDRxmhBCZtjLm9upnUpNYmsdbpoEUNiZ7 7Y7vNQgv77tM+OAHK874a72YamzdqBApWbw6uRu5aI1WIEeFFxBqMV9DIsqG1avdl8Hi 9yuhpMXGSue/uMg/bY9mqwCDraDWRt8kvs+HIxpZOC/vfpiKngHJQ/NZH4mB4xINH1qd gleg== X-Forwarded-Encrypted: i=1; AJvYcCVrWSSHvHXzxFgWjDEpStqlKrimRaaemtnBxQFkK4JHV95NhVojpfINeevaAfilFUigy84I5pvB7LgJvCk=@vger.kernel.org X-Gm-Message-State: AOJu0YzjCsAQmmkIbV0sYaVFiDmB9FNUV6DzCr9ON0qAyIF0DAXpefH0 Ri67VRU4X8rzHltFquGZjEFfghN+GBtikyfzcx3JkD0/lJhybtCpcbdB X-Gm-Gg: ASbGncv8lGBf8DYFi37bVC2jVgXauTkG/epMBDZijICSIlbJCRNMI1Z162lueqn8X5J 3SHWMPUCyYTPO3nu5OG9hsEcWCVFwvbIgx7ZKml0SfMKb//f6qASkDgUDE6owiiajEISgCdMSrZ 6sWdfe17LClAMnuSIo4XGXJHSNSuhWQRHEjtE4JlXbuL4vjREphay+7bTc7STs2Z5aYBWDe0Etl s0tMS0b1qtuuMvzR3DXGG46d/205YZVOc8pl7nnZMw6id5fRL0YOQfa8Fzn0CyG21w58EyA0GnN jc1HGA75FCOUGAx3HO7C5mwHKpalGlxtBtttE2Y3TGoLNr/cwTR0NaV+ypd9cog44EZ5gmI551Q 5bf7/rBZPjjjTWTtQJAHALGY2pcnH5iYk0g6IRz7dY1HWsVXKUx6jiDgBHvIJVxgVKhNyskULBj kKRf/v3RzHQM7NzHQQSPLErVApKFZfhowTKiCG2gt283g= X-Google-Smtp-Source: AGHT+IGuMYHt7WIQD1fK0EiihxrlnrbJ5cDcN1SmyPvVx87IncetjCE6sVwVUYILV4vleroj1LiXDQ== X-Received: by 2002:a17:902:ce12:b0:27e:ec72:f62 with SMTP id d9443c01a7336-290c9c89b06mr180684945ad.6.1761020446906; Mon, 20 Oct 2025 21:20:46 -0700 (PDT) Received: from Barrys-MBP.hub ([47.72.128.212]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-292471fde15sm96162725ad.84.2025.10.20.21.20.41 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Mon, 20 Oct 2025 21:20:46 -0700 (PDT) From: Barry Song <21cnbao@gmail.com> To: linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, sumit.semwal@linaro.org Cc: 21cnbao@gmail.com, Brian.Starkey@arm.com, benjamin.gaignard@collabora.com, christian.koenig@amd.com, dri-devel@lists.freedesktop.org, jstultz@google.com, tjmercier@google.com, v-songbaohua@oppo.com, zhengtangquan@oppo.com Subject: [PATCH v2] dma-buf: system_heap: use larger contiguous mappings instead of per-page mmap Date: Tue, 21 Oct 2025 17:20:22 +1300 Message-Id: <20251021042022.47919-1-21cnbao@gmail.com> X-Mailer: git-send-email 2.39.3 (Apple Git-146) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Barry Song We can allocate high-order pages, but mapping them one by one is inefficient. This patch changes the code to map as large a chunk as possible. The code looks somewhat complicated mainly because supporting mmap with a non-zero offset is a bit tricky. Using the micro-benchmark below, we see that mmap becomes 3.5X faster: #include #include #include #include #include #include #include #include #define SIZE (512UL * 1024 * 1024) #define PAGE 4096 #define STRIDE (PAGE/sizeof(int)) #define PAGES (SIZE/PAGE) int main(void) { int heap =3D open("/dev/dma_heap/system", O_RDONLY); struct dma_heap_allocation_data d =3D { .len =3D SIZE, .fd_flags =3D O_RDWR|O_CLOEXEC }; ioctl(heap, DMA_HEAP_IOCTL_ALLOC, &d); struct timespec t0, t1; clock_gettime(CLOCK_MONOTONIC, &t0); int *p =3D mmap(NULL, SIZE, PROT_READ|PROT_WRITE, MAP_SHARED, d.fd, 0= ); clock_gettime(CLOCK_MONOTONIC, &t1); for (int i =3D 0; i < PAGES; i++) p[i*STRIDE] =3D i; for (int i =3D 0; i < PAGES; i++) if (p[i*STRIDE] !=3D i) { fprintf(stderr, "mismatch at page %d\n", i); exit(1); } long ns =3D (t1.tv_sec-t0.tv_sec)*1000000000L + (t1.tv_nsec-t0.tv_nsec); printf("mmap 512MB took %.3f us, verify OK\n", ns/1000.0); return 0; } W/ patch: ~ # ./a.out mmap 512MB took 200266.000 us, verify OK ~ # ./a.out mmap 512MB took 198151.000 us, verify OK ~ # ./a.out mmap 512MB took 197069.000 us, verify OK ~ # ./a.out mmap 512MB took 196781.000 us, verify OK ~ # ./a.out mmap 512MB took 198102.000 us, verify OK ~ # ./a.out mmap 512MB took 195552.000 us, verify OK W/o patch: ~ # ./a.out mmap 512MB took 6987470.000 us, verify OK ~ # ./a.out mmap 512MB took 6970739.000 us, verify OK ~ # ./a.out mmap 512MB took 6984383.000 us, verify OK ~ # ./a.out mmap 512MB took 6971311.000 us, verify OK ~ # ./a.out mmap 512MB took 6991680.000 us, verify OK Signed-off-by: Barry Song Acked-by: John Stultz Reviewed-by: Maxime Ripard --- -v2: collect John's ack. thanks! drivers/dma-buf/heaps/system_heap.c | 33 +++++++++++++++++++++-------- 1 file changed, 24 insertions(+), 9 deletions(-) diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/sy= stem_heap.c index bbe7881f1360..4c782fe33fd4 100644 --- a/drivers/dma-buf/heaps/system_heap.c +++ b/drivers/dma-buf/heaps/system_heap.c @@ -186,20 +186,35 @@ static int system_heap_mmap(struct dma_buf *dmabuf, s= truct vm_area_struct *vma) struct system_heap_buffer *buffer =3D dmabuf->priv; struct sg_table *table =3D &buffer->sg_table; unsigned long addr =3D vma->vm_start; - struct sg_page_iter piter; - int ret; + unsigned long pgoff =3D vma->vm_pgoff; + struct scatterlist *sg; + int i, ret; + + for_each_sgtable_sg(table, sg, i) { + unsigned long n =3D sg->length >> PAGE_SHIFT; =20 - for_each_sgtable_page(table, &piter, vma->vm_pgoff) { - struct page *page =3D sg_page_iter_page(&piter); + if (pgoff < n) + break; + pgoff -=3D n; + } + + for (; sg && addr < vma->vm_end; sg =3D sg_next(sg)) { + unsigned long n =3D (sg->length >> PAGE_SHIFT) - pgoff; + struct page *page =3D sg_page(sg) + pgoff; + unsigned long size =3D n << PAGE_SHIFT; + + if (addr + size > vma->vm_end) + size =3D vma->vm_end - addr; =20 - ret =3D remap_pfn_range(vma, addr, page_to_pfn(page), PAGE_SIZE, - vma->vm_page_prot); + ret =3D remap_pfn_range(vma, addr, page_to_pfn(page), + size, vma->vm_page_prot); if (ret) return ret; - addr +=3D PAGE_SIZE; - if (addr >=3D vma->vm_end) - return 0; + + addr +=3D size; + pgoff =3D 0; } + return 0; } =20 --=20 2.39.3 (Apple Git-146)