[PATCH 1/2] drm/ttm: swap consecutive allocated cached pages v2

He, Roger Hongbo.He at amd.com
Mon Dec 4 12:22:34 UTC 2017

-----Original Message-----
From: Christian König [mailto:ckoenig.leichtzumerken at gmail.com] 
Sent: Monday, December 04, 2017 8:13 PM
To: dri-devel at lists.freedesktop.org; amd-gfx at lists.freedesktop.org; He, Roger <Hongbo.He at amd.com>; ckoenig.leichtzumerken at gmail.com
Subject: [PATCH 1/2] drm/ttm: swap consecutive allocated cached pages v2

When we detect consecutive allocation of pages swap them to avoid accidentally freeing them as huge page.

v2: use swap

Signed-off-by: Christian König <christian.koenig at amd.com>
 drivers/gpu/drm/ttm/ttm_page_alloc.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc.c b/drivers/gpu/drm/ttm/ttm_page_alloc.c
index c82d94cbbabc..b6c5148607e9 100644
--- a/drivers/gpu/drm/ttm/ttm_page_alloc.c
+++ b/drivers/gpu/drm/ttm/ttm_page_alloc.c
@@ -921,6 +921,10 @@ static int ttm_get_pages(struct page **pages, unsigned npages, int flags,
 				return -ENOMEM;
How about add first index as below?

		first = i;  //init  first here
		while (npages) {
			p = alloc_page(gfp_flags);
			if (!p) {
				pr_debug("Unable to allocate page\n");
				return -ENOMEM;
			/* Swap the pages if we detect consecutive order */
			if (i > first && pages[i - 1] == p - 1)                                          //change to (i > first), because I worry if npages is 513, the first regular page is exactly consecutive with last page of huge page. Then swap them is not what I want here.
				swap(p, pages[i - 1]);

			pages[i++] = p;

 			pages[i++] = p;

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