[PATCH RESEND v3 2/3] drm/ttm: Reduce the number of used allocation orders for TTM pages
Christian König
christian.koenig at amd.com
Wed Apr 12 14:17:52 UTC 2023
Am 12.04.23 um 11:08 schrieb Daniel Vetter:
> On Tue, 11 Apr 2023 at 15:45, Daniel Vetter <daniel at ffwll.ch> wrote:
>> On Tue, Apr 11, 2023 at 02:11:18PM +0200, Christian König wrote:
>>> Am 11.04.23 um 11:51 schrieb Daniel Vetter:
>>>> On Tue, Apr 04, 2023 at 10:06:49PM +0200, Thomas Hellström wrote:
>>>>> When swapping out, we will split multi-order pages both in order to
>>>>> move them to the swap-cache and to be able to return memory to the
>>>>> swap cache as soon as possible on a page-by-page basis.
>>>>> Reduce the page max order to the system PMD size, as we can then be nicer
>>>>> to the system and avoid splitting gigantic pages.
>>>>>
>>>>> Looking forward to when we might be able to swap out PMD size folios
>>>>> without splitting, this will also be a benefit.
>>>>>
>>>>> v2:
>>>>> - Include all orders up to the PMD size (Christian König)
>>>>> v3:
>>>>> - Avoid compilation errors for architectures with special PFN_SHIFTs
>>>>>
>>>>> Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
>>>>> Reviewed-by: Christian König <christian.koenig at amd.com>
>>>> Apparently this fails on ppc build testing. Please supply build fix asap
>>>> (or I guess we need to revert). I'm kinda not clear why this only showed
>>>> up when I merged the drm-misc-next pr into drm-next ...
>>> I'm really wondering this as well. It looks like PMD_SHIFT isn't a constant
>>> on this particular platform.
>>>
>>> But from what I can find in the upstream 6.2 kernel PMD_SHIFT always seems
>>> to be a constant.
>>>
>>> So how exactly can that here break?
>> There's some in-flight patches to rework MAX_ORDER and other things in
>> linux-next, maybe it's recent? If you check out linux-next then you need
>> to reapply the patch (since sfr reverted it).
> So I looked and on ppc64 PMD_SHIFT is defined in terms of
> PTE_INDEX_SIZE, which is defined (for book3s) in terms of the variable
> __pte_index_size. This is in 6.3 already and seems pretty old.
Ah! I missed that one, thanks.
> So revert? Or fixup patch to make this work on ppc?
I think for now just revert or change it so that we check if PMD_SHIFT
is a constant.
Thomas do you have any quick solution?
Christian.
>
>
>>>>> ---
>>>>> drivers/gpu/drm/ttm/ttm_pool.c | 30 +++++++++++++++++++-----------
>>>>> 1 file changed, 19 insertions(+), 11 deletions(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c
>>>>> index dfce896c4bae..18c342a919a2 100644
>>>>> --- a/drivers/gpu/drm/ttm/ttm_pool.c
>>>>> +++ b/drivers/gpu/drm/ttm/ttm_pool.c
>>>>> @@ -47,6 +47,11 @@
>>>>> #include "ttm_module.h"
>>>>> +#define TTM_MAX_ORDER (PMD_SHIFT - PAGE_SHIFT)
>>>>> +#define __TTM_DIM_ORDER (TTM_MAX_ORDER + 1)
>>>>> +/* Some architectures have a weird PMD_SHIFT */
>>>>> +#define TTM_DIM_ORDER (__TTM_DIM_ORDER <= MAX_ORDER ? __TTM_DIM_ORDER : MAX_ORDER)
>>>>> +
>>>>> /**
>>>>> * struct ttm_pool_dma - Helper object for coherent DMA mappings
>>>>> *
>>>>> @@ -65,11 +70,11 @@ module_param(page_pool_size, ulong, 0644);
>>>>> static atomic_long_t allocated_pages;
>>>>> -static struct ttm_pool_type global_write_combined[MAX_ORDER];
>>>>> -static struct ttm_pool_type global_uncached[MAX_ORDER];
>>>>> +static struct ttm_pool_type global_write_combined[TTM_DIM_ORDER];
>>>>> +static struct ttm_pool_type global_uncached[TTM_DIM_ORDER];
>>>>> -static struct ttm_pool_type global_dma32_write_combined[MAX_ORDER];
>>>>> -static struct ttm_pool_type global_dma32_uncached[MAX_ORDER];
>>>>> +static struct ttm_pool_type global_dma32_write_combined[TTM_DIM_ORDER];
>>>>> +static struct ttm_pool_type global_dma32_uncached[TTM_DIM_ORDER];
>>>>> static spinlock_t shrinker_lock;
>>>>> static struct list_head shrinker_list;
>>>>> @@ -444,7 +449,7 @@ int ttm_pool_alloc(struct ttm_pool *pool, struct ttm_tt *tt,
>>>>> else
>>>>> gfp_flags |= GFP_HIGHUSER;
>>>>> - for (order = min_t(unsigned int, MAX_ORDER - 1, __fls(num_pages));
>>>>> + for (order = min_t(unsigned int, TTM_MAX_ORDER, __fls(num_pages));
>>>>> num_pages;
>>>>> order = min_t(unsigned int, order, __fls(num_pages))) {
>>>>> struct ttm_pool_type *pt;
>>>>> @@ -563,7 +568,7 @@ void ttm_pool_init(struct ttm_pool *pool, struct device *dev,
>>>>> if (use_dma_alloc) {
>>>>> for (i = 0; i < TTM_NUM_CACHING_TYPES; ++i)
>>>>> - for (j = 0; j < MAX_ORDER; ++j)
>>>>> + for (j = 0; j < TTM_DIM_ORDER; ++j)
>>>>> ttm_pool_type_init(&pool->caching[i].orders[j],
>>>>> pool, i, j);
>>>>> }
>>>>> @@ -583,7 +588,7 @@ void ttm_pool_fini(struct ttm_pool *pool)
>>>>> if (pool->use_dma_alloc) {
>>>>> for (i = 0; i < TTM_NUM_CACHING_TYPES; ++i)
>>>>> - for (j = 0; j < MAX_ORDER; ++j)
>>>>> + for (j = 0; j < TTM_DIM_ORDER; ++j)
>>>>> ttm_pool_type_fini(&pool->caching[i].orders[j]);
>>>>> }
>>>>> @@ -637,7 +642,7 @@ static void ttm_pool_debugfs_header(struct seq_file *m)
>>>>> unsigned int i;
>>>>> seq_puts(m, "\t ");
>>>>> - for (i = 0; i < MAX_ORDER; ++i)
>>>>> + for (i = 0; i < TTM_DIM_ORDER; ++i)
>>>>> seq_printf(m, " ---%2u---", i);
>>>>> seq_puts(m, "\n");
>>>>> }
>>>>> @@ -648,7 +653,7 @@ static void ttm_pool_debugfs_orders(struct ttm_pool_type *pt,
>>>>> {
>>>>> unsigned int i;
>>>>> - for (i = 0; i < MAX_ORDER; ++i)
>>>>> + for (i = 0; i < TTM_DIM_ORDER; ++i)
>>>>> seq_printf(m, " %8u", ttm_pool_type_count(&pt[i]));
>>>>> seq_puts(m, "\n");
>>>>> }
>>>>> @@ -751,13 +756,16 @@ int ttm_pool_mgr_init(unsigned long num_pages)
>>>>> {
>>>>> unsigned int i;
>>>>> + BUILD_BUG_ON(TTM_DIM_ORDER > MAX_ORDER);
>>>>> + BUILD_BUG_ON(TTM_DIM_ORDER < 1);
>>>>> +
>>>>> if (!page_pool_size)
>>>>> page_pool_size = num_pages;
>>>>> spin_lock_init(&shrinker_lock);
>>>>> INIT_LIST_HEAD(&shrinker_list);
>>>>> - for (i = 0; i < MAX_ORDER; ++i) {
>>>>> + for (i = 0; i < TTM_DIM_ORDER; ++i) {
>>>>> ttm_pool_type_init(&global_write_combined[i], NULL,
>>>>> ttm_write_combined, i);
>>>>> ttm_pool_type_init(&global_uncached[i], NULL, ttm_uncached, i);
>>>>> @@ -790,7 +798,7 @@ void ttm_pool_mgr_fini(void)
>>>>> {
>>>>> unsigned int i;
>>>>> - for (i = 0; i < MAX_ORDER; ++i) {
>>>>> + for (i = 0; i < TTM_DIM_ORDER; ++i) {
>>>>> ttm_pool_type_fini(&global_write_combined[i]);
>>>>> ttm_pool_type_fini(&global_uncached[i]);
>>>>> --
>>>>> 2.39.2
>>>>>
>> --
>> Daniel Vetter
>> Software Engineer, Intel Corporation
>> http://blog.ffwll.ch
>
>
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