Re: [PATCH RESEND v3 2/3] drm/ttm: Reduce the number of used allocation orders for TTM pages

[Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>]

Hi

On 4/14/23 12:11, Christian König wrote:
> Am 13.04.23 um 15:13 schrieb Daniel Vetter:
> > On Thu, 13 Apr 2023 at 11:46, Christian König 
> > <christian.koenig@xxxxxxx> wrote:
> > > Am 13.04.23 um 10:48 schrieb Daniel Vetter:
> > > > On Wed, 12 Apr 2023 at 16:18, Christian König 
> > > > <christian.koenig@xxxxxxx> wrote:
> > > > > Am 12.04.23 um 11:08 schrieb Daniel Vetter:
> > > > > > On Tue, 11 Apr 2023 at 15:45, Daniel Vetter <daniel@xxxxxxxx> 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@xxxxxxxxxxxxxxx>
> > > > > > > > > > Reviewed-by: Christian König <christian.koenig@xxxxxxx>
> > > > > > > > > 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?
> > > > I guess Thomas is on vacations. Can you pls do the revert and push it
> > > > to drm-misc-next-fixes so this won't get lost?
> > > The offending patch hasn't showed up in drm-misc-next-fixes nor
> > > drm-misc-fixes yet. Looks like the branches are lacking behind.
> > >
> > > I can revert it on drm-misc-next, but I', not 100% sure that will then
> > > get picked up in time.
> > It's there now, Maarten forwarded drm-misc-next-fixes this morning.
> > That's why I pinged here again, trees are ready to land the revert :-)
>
> Just pushed it.
>
> Christian.

Thanks for fixing this. (I was on vacation). I got a "BUILD SUCCESS" for 
this series based on drm-misc-next so I didn't think anything weird 
would show up.

Thanks,

Thomas

> > -Daniel
> >
> > > Christian.
> > >
> > > > Acked-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> > > >
> > > > preemptively for that. Normally I think we could wait a bit more but
> > > > it's really close to merge window PR and I don't like handing too many
> > > > open things to Dave when he's back :-)
> > > > -Daniel
> > > >
> > > > > 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