On Wed, May 15, 2019 at 10:38:28AM +0200, Daniel Vetter wrote:
> On Tue, May 14, 2019 at 02:31:18PM +0200, Christian König wrote:
> > From: Chunming Zhou <david1.zhou@xxxxxxx>
> >
> > heavy gpu job could occupy memory long time, which lead other user fail to get memory.
> >
> > basically pick up Christian idea:
> >
> > 1. Reserve the BO in DC using a ww_mutex ticket (trivial).
> > 2. If we then run into this EBUSY condition in TTM check if the BO we need memory for (or rather the ww_mutex of its reservation object) has a ticket assigned.
> > 3. If we have a ticket we grab a reference to the first BO on the LRU, drop the LRU lock and try to grab the reservation lock with the ticket.
> > 4. If getting the reservation lock with the ticket succeeded we check if the BO is still the first one on the LRU in question (the BO could have moved).
> > 5. If the BO is still the first one on the LRU in question we try to evict it as we would evict any other BO.
> > 6. If any of the "If's" above fail we just back off and return -EBUSY.
> >
> > v2: fix some minor check
> > v3: address Christian v2 comments.
> > v4: fix some missing
> > v5: handle first_bo unlock and bo_get/put
> > v6: abstract unified iterate function, and handle all possible usecase not only pinned bo.
> > v7: pass request bo->resv to ttm_bo_evict_first
> > v8 (chk): minimal coding style fix
> >
> > Change-Id: I21423fb922f885465f13833c41df1e134364a8e7
> > Signed-off-by: Chunming Zhou <david1.zhou@xxxxxxx>
> > Reviewed-by: Christian König <christian.koenig@xxxxxxx>
>
> I think this closes a big gap between ttm and the bkl/struct_mutex
> drivers - it's much easier to guarantee you can evict everything if
> there's only a single lock :-)
>
> Would be absolutely awesome if we could extract this as some kind of
> building block, like we've done with lots of other ttm concepts already
> (reservation_obj, fences, ...).
>
> Just an aside really.
Ofc this is meant as a comment on the entire patch series, without all the
other patches to make sure BO always stay on a relevant LRU there's still
gaps in the guaranteed forward progress eviction algorithm.
-Daniel
> -Daniel
>
> > ---
> > drivers/gpu/drm/ttm/ttm_bo.c | 113 +++++++++++++++++++++++++++++------
> > 1 file changed, 96 insertions(+), 17 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> > index 2845fceb2fbd..e634d3a36923 100644
> > --- a/drivers/gpu/drm/ttm/ttm_bo.c
> > +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> > @@ -766,11 +766,13 @@ EXPORT_SYMBOL(ttm_bo_eviction_valuable);
> > * b. Otherwise, trylock it.
> > */
> > static bool ttm_bo_evict_swapout_allowable(struct ttm_buffer_object *bo,
> > - struct ttm_operation_ctx *ctx, bool *locked)
> > + struct ttm_operation_ctx *ctx, bool *locked, bool *busy)
> > {
> > bool ret = false;
> >
> > *locked = false;
> > + if (busy)
> > + *busy = false;
> > if (bo->resv == ctx->resv) {
> > reservation_object_assert_held(bo->resv);
> > if (ctx->flags & TTM_OPT_FLAG_ALLOW_RES_EVICT
> > @@ -779,35 +781,46 @@ static bool ttm_bo_evict_swapout_allowable(struct ttm_buffer_object *bo,
> > } else {
> > *locked = reservation_object_trylock(bo->resv);
> > ret = *locked;
> > + if (!ret && busy)
> > + *busy = true;
> > }
> >
> > return ret;
> > }
> >
> > -static int ttm_mem_evict_first(struct ttm_bo_device *bdev,
> > - uint32_t mem_type,
> > - const struct ttm_place *place,
> > - struct ttm_operation_ctx *ctx)
> > +static struct ttm_buffer_object*
> > +ttm_mem_find_evitable_bo(struct ttm_bo_device *bdev,
> > + struct ttm_mem_type_manager *man,
> > + const struct ttm_place *place,
> > + struct ttm_operation_ctx *ctx,
> > + struct ttm_buffer_object **first_bo,
> > + bool *locked)
> > {
> > - struct ttm_bo_global *glob = bdev->glob;
> > - struct ttm_mem_type_manager *man = &bdev->man[mem_type];
> > struct ttm_buffer_object *bo = NULL;
> > - bool locked = false;
> > - unsigned i;
> > - int ret;
> > + int i;
> >
> > - spin_lock(&glob->lru_lock);
> > + if (first_bo)
> > + *first_bo = NULL;
> > for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i) {
> > list_for_each_entry(bo, &man->lru[i], lru) {
> > - if (!ttm_bo_evict_swapout_allowable(bo, ctx, &locked))
> > + bool busy = false;
> > +
> > + if (!ttm_bo_evict_swapout_allowable(bo, ctx, locked,
> > + &busy)) {
> > + if (first_bo && !(*first_bo) && busy) {
> > + ttm_bo_get(bo);
> > + *first_bo = bo;
> > + }
> > continue;
> > + }
> >
> > if (place && !bdev->driver->eviction_valuable(bo,
> > place)) {
> > - if (locked)
> > + if (*locked)
> > reservation_object_unlock(bo->resv);
> > continue;
> > }
> > +
> > break;
> > }
> >
> > @@ -818,9 +831,69 @@ static int ttm_mem_evict_first(struct ttm_bo_device *bdev,
> > bo = NULL;
> > }
> >
> > + return bo;
> > +}
> > +
> > +static int ttm_mem_evict_first(struct ttm_bo_device *bdev,
> > + uint32_t mem_type,
> > + const struct ttm_place *place,
> > + struct ttm_operation_ctx *ctx,
> > + struct reservation_object *request_resv)
> > +{
> > + struct ttm_bo_global *glob = bdev->glob;
> > + struct ttm_mem_type_manager *man = &bdev->man[mem_type];
> > + struct ttm_buffer_object *bo = NULL, *first_bo = NULL;
> > + bool locked = false;
> > + int ret;
> > +
> > + spin_lock(&glob->lru_lock);
> > + bo = ttm_mem_find_evitable_bo(bdev, man, place, ctx, &first_bo,
> > + &locked);
> > if (!bo) {
> > + struct ww_acquire_ctx *acquire_ctx = request_resv->lock.ctx;
> > + struct ttm_operation_ctx busy_ctx;
> > +
> > spin_unlock(&glob->lru_lock);
> > - return -EBUSY;
> > + /* check if other user occupy memory too long time */
> > + if (!first_bo || !request_resv || !request_resv->lock.ctx) {
> > + if (first_bo)
> > + ttm_bo_put(first_bo);
> > + return -EBUSY;
> > + }
> > + if (first_bo->resv == request_resv) {
> > + ttm_bo_put(first_bo);
> > + return -EBUSY;
> > + }
> > + if (ctx->interruptible)
> > + ret = ww_mutex_lock_interruptible(&first_bo->resv->lock,
> > + acquire_ctx);
> > + else
> > + ret = ww_mutex_lock(&first_bo->resv->lock,
> > + acquire_ctx);
> > + if (ret) {
> > + ttm_bo_put(first_bo);
> > + return ret;
> > + }
> > + spin_lock(&glob->lru_lock);
> > + /* previous busy resv lock is held by above, idle now,
> > + * so let them evictable.
> > + */
> > + busy_ctx.interruptible = ctx->interruptible;
> > + busy_ctx.no_wait_gpu = ctx->no_wait_gpu;
> > + busy_ctx.resv = first_bo->resv;
> > + busy_ctx.flags = TTM_OPT_FLAG_ALLOW_RES_EVICT;
> > +
> > + bo = ttm_mem_find_evitable_bo(bdev, man, place, &busy_ctx, NULL,
> > + &locked);
> > + if (bo && (bo->resv == first_bo->resv))
> > + locked = true;
> > + else if (bo)
> > + ww_mutex_unlock(&first_bo->resv->lock);
> > + if (!bo) {
> > + spin_unlock(&glob->lru_lock);
> > + ttm_bo_put(first_bo);
> > + return -EBUSY;
> > + }
> > }
> >
> > kref_get(&bo->list_kref);
> > @@ -829,11 +902,15 @@ static int ttm_mem_evict_first(struct ttm_bo_device *bdev,
> > ret = ttm_bo_cleanup_refs(bo, ctx->interruptible,
> > ctx->no_wait_gpu, locked);
> > kref_put(&bo->list_kref, ttm_bo_release_list);
> > + if (first_bo)
> > + ttm_bo_put(first_bo);
> > return ret;
> > }
> >
> > ttm_bo_del_from_lru(bo);
> > spin_unlock(&glob->lru_lock);
> > + if (first_bo)
> > + ttm_bo_put(first_bo);
> >
> > ret = ttm_bo_evict(bo, ctx);
> > if (locked) {
> > @@ -907,7 +984,7 @@ static int ttm_bo_mem_force_space(struct ttm_buffer_object *bo,
> > return ret;
> > if (mem->mm_node)
> > break;
> > - ret = ttm_mem_evict_first(bdev, mem_type, place, ctx);
> > + ret = ttm_mem_evict_first(bdev, mem_type, place, ctx, bo->resv);
> > if (unlikely(ret != 0))
> > return ret;
> > } while (1);
> > @@ -1401,7 +1478,8 @@ static int ttm_bo_force_list_clean(struct ttm_bo_device *bdev,
> > for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i) {
> > while (!list_empty(&man->lru[i])) {
> > spin_unlock(&glob->lru_lock);
> > - ret = ttm_mem_evict_first(bdev, mem_type, NULL, &ctx);
> > + ret = ttm_mem_evict_first(bdev, mem_type, NULL, &ctx,
> > + NULL);
> > if (ret)
> > return ret;
> > spin_lock(&glob->lru_lock);
> > @@ -1772,7 +1850,8 @@ int ttm_bo_swapout(struct ttm_bo_global *glob, struct ttm_operation_ctx *ctx)
> > spin_lock(&glob->lru_lock);
> > for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i) {
> > list_for_each_entry(bo, &glob->swap_lru[i], swap) {
> > - if (ttm_bo_evict_swapout_allowable(bo, ctx, &locked)) {
> > + if (ttm_bo_evict_swapout_allowable(bo, ctx, &locked,
> > + NULL)) {
> > ret = 0;
> > break;
> > }
> > --
> > 2.17.1
> >
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@xxxxxxxxxxxxxxxxxxxxx
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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