Hmm,
This zone was intended to stop TTM page allocations from exhausting the
DMA32 zone. IIRC dma_alloc_coherent() uses DMA32 by default, which means
if we drop this check, other devices may stop functioning unexpectedly?
However, in the end I'd expect the kernel page allocation system to make
sure there are some pages left in the DMA32 zone, otherwise random
non-IO page allocations would also potentially exhaust the DMA32 zone
without anybody caring, which means removing this zone wouldn't be any
worse than whatever other subsystems may be doing already...
/Thomas
On 2/16/19 12:02 AM, Kuehling, Felix wrote:
This is an RFC. I'm not sure this is the right solution, but it
highlights the problem I'm trying to solve.
The dma32_zone limits the acc_size of all allocated BOs to 2GB. On a
64-bit system with hundreds of GB of system memory and GPU memory,
this can become a bottle neck. We're seeing TTM memory allocation
failures not because we're truly out of memory, but because we're
out of space in the dma32_zone for the acc_size needed for our BO
book-keeping.
Signed-off-by: Felix Kuehling <Felix.Kuehling@xxxxxxx>
CC: thellstrom@xxxxxxxxxx
CC: christian.koenig@xxxxxxx
---
drivers/gpu/drm/ttm/ttm_memory.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_memory.c b/drivers/gpu/drm/ttm/ttm_memory.c
index f1567c3..bb05365 100644
--- a/drivers/gpu/drm/ttm/ttm_memory.c
+++ b/drivers/gpu/drm/ttm/ttm_memory.c
@@ -363,7 +363,7 @@ static int ttm_mem_init_highmem_zone(struct ttm_mem_global *glob,
glob->zones[glob->num_zones++] = zone;
return 0;
}
-#else
+#elifndef CONFIG_64BIT
static int ttm_mem_init_dma32_zone(struct ttm_mem_global *glob,
const struct sysinfo *si)
{
@@ -441,7 +441,7 @@ int ttm_mem_global_init(struct ttm_mem_global *glob)
ret = ttm_mem_init_highmem_zone(glob, &si);
if (unlikely(ret != 0))
goto out_no_zone;
-#else
+#elifndef CONFIG_64BIT
ret = ttm_mem_init_dma32_zone(glob, &si);
if (unlikely(ret != 0))
goto out_no_zone;
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