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Subject[PATCH 2/2] drm/ttm: Use GFP_TRANSHUGE_LIGHT for allocating huge pages
Date
From: Michel Dänzer <michel.daenzer@amd.com>

GFP_TRANSHUGE tries very hard to allocate huge pages, which can result
in long delays with high memory pressure. I have observed firefox
freezing for up to around a minute due to this while restic was taking
a full system backup.

Since we don't really need huge pages, use GFP_TRANSHUGE_LIGHT |
__GFP_NORETRY instead, in order to fail quickly when there are no huge
pages available.

Set __GFP_KSWAPD_RECLAIM as well, in order for huge pages to be freed
up in the background if necessary.

With these changes, I'm no longer seeing freezes during a restic backup.

Cc: stable@vger.kernel.org
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
---
drivers/gpu/drm/ttm/ttm_page_alloc.c | 11 ++++++++---
drivers/gpu/drm/ttm/ttm_page_alloc_dma.c | 3 ++-
2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc.c b/drivers/gpu/drm/ttm/ttm_page_alloc.c
index 2ce91272b111..6794f15461d9 100644
--- a/drivers/gpu/drm/ttm/ttm_page_alloc.c
+++ b/drivers/gpu/drm/ttm/ttm_page_alloc.c
@@ -914,7 +914,8 @@ static int ttm_get_pages(struct page **pages, unsigned npages, int flags,
while (npages >= HPAGE_PMD_NR) {
gfp_t huge_flags = gfp_flags;

- huge_flags |= GFP_TRANSHUGE;
+ huge_flags |= GFP_TRANSHUGE_LIGHT | __GFP_NORETRY |
+ __GFP_KSWAPD_RECLAIM;
huge_flags &= ~__GFP_MOVABLE;
huge_flags &= ~__GFP_COMP;
p = alloc_pages(huge_flags, HPAGE_PMD_ORDER);
@@ -1033,11 +1034,15 @@ int ttm_page_alloc_init(struct ttm_mem_global *glob, unsigned max_pages)
GFP_USER | GFP_DMA32, "uc dma", 0);

ttm_page_pool_init_locked(&_manager->wc_pool_huge,
- GFP_TRANSHUGE & ~(__GFP_MOVABLE | __GFP_COMP),
+ (GFP_TRANSHUGE_LIGHT | __GFP_NORETRY |
+ __GFP_KSWAPD_RECLAIM) &
+ ~(__GFP_MOVABLE | __GFP_COMP),
"wc huge", order);

ttm_page_pool_init_locked(&_manager->uc_pool_huge,
- GFP_TRANSHUGE & ~(__GFP_MOVABLE | __GFP_COMP)
+ (GFP_TRANSHUGE_LIGHT | __GFP_NORETRY |
+ __GFP_KSWAPD_RECLAIM) &
+ ~(__GFP_MOVABLE | __GFP_COMP)
, "uc huge", order);

_manager->options.max_size = max_pages;
diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
index 291b04213ec5..5a551158c289 100644
--- a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
+++ b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
@@ -910,7 +910,8 @@ static gfp_t ttm_dma_pool_gfp_flags(struct ttm_dma_tt *ttm_dma, bool huge)
gfp_flags |= __GFP_ZERO;

if (huge) {
- gfp_flags |= GFP_TRANSHUGE;
+ gfp_flags |= GFP_TRANSHUGE_LIGHT | __GFP_NORETRY |
+ __GFP_KSWAPD_RECLAIM;
gfp_flags &= ~__GFP_MOVABLE;
gfp_flags &= ~__GFP_COMP;
}
--
2.17.0
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