On 05/11/2022 23:27, Dmitry Osipenko wrote:
> Replace Panfrost's custom memory shrinker with a common drm-shmem
> memory shrinker.
>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
Sadly this triggers GPU faults under memory pressure - it looks
suspiciously like mappings are being freed while the jobs are still running.
I'm not sure I understand how the generic shrinker replicates the
"gpu_usecount" atomic that Panfrost currently has, and I'm wondering if
that's the cause?
Also just reverting this commit (so just patches 1-6) I can't actually
get Panfrost to purge any memory. So I don't think the changes (most
likely in patch 4) are quite right either.
At the moment I don't have the time to investigate in detail. But if
you've any ideas for something specific I should look at I can run more
testing.
Steve
> ---
> drivers/gpu/drm/panfrost/Makefile | 1 -
> drivers/gpu/drm/panfrost/panfrost_device.h | 4 -
> drivers/gpu/drm/panfrost/panfrost_drv.c | 19 +--
> drivers/gpu/drm/panfrost/panfrost_gem.c | 33 +++--
> drivers/gpu/drm/panfrost/panfrost_gem.h | 9 --
> .../gpu/drm/panfrost/panfrost_gem_shrinker.c | 129 ------------------
> drivers/gpu/drm/panfrost/panfrost_job.c | 18 ++-
> 7 files changed, 42 insertions(+), 171 deletions(-)
> delete mode 100644 drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
>
> diff --git a/drivers/gpu/drm/panfrost/Makefile b/drivers/gpu/drm/panfrost/Makefile
> index 7da2b3f02ed9..11622e22cf15 100644
> --- a/drivers/gpu/drm/panfrost/Makefile
> +++ b/drivers/gpu/drm/panfrost/Makefile
> @@ -5,7 +5,6 @@ panfrost-y := \
> panfrost_device.o \
> panfrost_devfreq.o \
> panfrost_gem.o \
> - panfrost_gem_shrinker.o \
> panfrost_gpu.o \
> panfrost_job.o \
> panfrost_mmu.o \
> diff --git a/drivers/gpu/drm/panfrost/panfrost_device.h b/drivers/gpu/drm/panfrost/panfrost_device.h
> index 8b25278f34c8..fe04b21fc044 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_device.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_device.h
> @@ -115,10 +115,6 @@ struct panfrost_device {
> atomic_t pending;
> } reset;
>
> - struct mutex shrinker_lock;
> - struct list_head shrinker_list;
> - struct shrinker shrinker;
> -
> struct panfrost_devfreq pfdevfreq;
> };
>
> diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
> index 94b8e6de34b8..fe78d5c75abf 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_drv.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
> @@ -160,7 +160,6 @@ panfrost_lookup_bos(struct drm_device *dev,
> break;
> }
>
> - atomic_inc(&bo->gpu_usecount);
> job->mappings[i] = mapping;
> }
>
> @@ -392,7 +391,6 @@ static int panfrost_ioctl_madvise(struct drm_device *dev, void *data,
> {
> struct panfrost_file_priv *priv = file_priv->driver_priv;
> struct drm_panfrost_madvise *args = data;
> - struct panfrost_device *pfdev = dev->dev_private;
> struct drm_gem_object *gem_obj;
> struct panfrost_gem_object *bo;
> int ret = 0;
> @@ -409,7 +407,6 @@ static int panfrost_ioctl_madvise(struct drm_device *dev, void *data,
> if (ret)
> goto out_put_object;
>
> - mutex_lock(&pfdev->shrinker_lock);
> mutex_lock(&bo->mappings.lock);
> if (args->madv == PANFROST_MADV_DONTNEED) {
> struct panfrost_gem_mapping *first;
> @@ -435,17 +432,8 @@ static int panfrost_ioctl_madvise(struct drm_device *dev, void *data,
>
> args->retained = drm_gem_shmem_madvise(&bo->base, args->madv);
>
> - if (args->retained) {
> - if (args->madv == PANFROST_MADV_DONTNEED)
> - list_move_tail(&bo->base.madv_list,
> - &pfdev->shrinker_list);
> - else if (args->madv == PANFROST_MADV_WILLNEED)
> - list_del_init(&bo->base.madv_list);
> - }
> -
> out_unlock_mappings:
> mutex_unlock(&bo->mappings.lock);
> - mutex_unlock(&pfdev->shrinker_lock);
> dma_resv_unlock(bo->base.base.resv);
> out_put_object:
> drm_gem_object_put(gem_obj);
> @@ -577,9 +565,6 @@ static int panfrost_probe(struct platform_device *pdev)
> ddev->dev_private = pfdev;
> pfdev->ddev = ddev;
>
> - mutex_init(&pfdev->shrinker_lock);
> - INIT_LIST_HEAD(&pfdev->shrinker_list);
> -
> err = panfrost_device_init(pfdev);
> if (err) {
> if (err != -EPROBE_DEFER)
> @@ -601,7 +586,7 @@ static int panfrost_probe(struct platform_device *pdev)
> if (err < 0)
> goto err_out1;
>
> - panfrost_gem_shrinker_init(ddev);
> + drm_gem_shmem_shrinker_register(ddev, "panfrost-shrinker");
>
> return 0;
>
> @@ -619,8 +604,8 @@ static int panfrost_remove(struct platform_device *pdev)
> struct panfrost_device *pfdev = platform_get_drvdata(pdev);
> struct drm_device *ddev = pfdev->ddev;
>
> + drm_gem_shmem_shrinker_unregister(ddev);
> drm_dev_unregister(ddev);
> - panfrost_gem_shrinker_cleanup(ddev);
>
> pm_runtime_get_sync(pfdev->dev);
> pm_runtime_disable(pfdev->dev);
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/panfrost/panfrost_gem.c
> index 293e799e2fe8..f1436405e3a0 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_gem.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_gem.c
> @@ -19,16 +19,6 @@ static void panfrost_gem_free_object(struct drm_gem_object *obj)
> struct panfrost_gem_object *bo = to_panfrost_bo(obj);
> struct panfrost_device *pfdev = obj->dev->dev_private;
>
> - /*
> - * Make sure the BO is no longer inserted in the shrinker list before
> - * taking care of the destruction itself. If we don't do that we have a
> - * race condition between this function and what's done in
> - * panfrost_gem_shrinker_scan().
> - */
> - mutex_lock(&pfdev->shrinker_lock);
> - list_del_init(&bo->base.madv_list);
> - mutex_unlock(&pfdev->shrinker_lock);
> -
> /*
> * If we still have mappings attached to the BO, there's a problem in
> * our refcounting.
> @@ -209,6 +199,25 @@ static const struct drm_gem_object_funcs panfrost_gem_funcs = {
> .vm_ops = &drm_gem_shmem_vm_ops,
> };
>
> +static int panfrost_shmem_evict(struct drm_gem_shmem_object *shmem)
> +{
> + struct panfrost_gem_object *bo = to_panfrost_bo(&shmem->base);
> +
> + if (!drm_gem_shmem_is_purgeable(shmem))
> + return -EOPNOTSUPP;
> +
> + if (!mutex_trylock(&bo->mappings.lock))
> + return -EBUSY;
> +
> + panfrost_gem_teardown_mappings_locked(bo);
> +
> + drm_gem_shmem_purge(shmem);
> +
> + mutex_unlock(&bo->mappings.lock);
> +
> + return 0;
> +}
> +
> /**
> * panfrost_gem_create_object - Implementation of driver->gem_create_object.
> * @dev: DRM device
> @@ -230,6 +239,7 @@ struct drm_gem_object *panfrost_gem_create_object(struct drm_device *dev, size_t
> mutex_init(&obj->mappings.lock);
> obj->base.base.funcs = &panfrost_gem_funcs;
> obj->base.map_wc = !pfdev->coherent;
> + obj->base.evict = panfrost_shmem_evict;
>
> return &obj->base.base;
> }
> @@ -266,6 +276,9 @@ panfrost_gem_create_with_handle(struct drm_file *file_priv,
> if (ret)
> return ERR_PTR(ret);
>
> + if (!bo->is_heap)
> + drm_gem_shmem_set_purgeable(shmem);
> +
> return bo;
> }
>
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.h b/drivers/gpu/drm/panfrost/panfrost_gem.h
> index 8088d5fd8480..09da064f1c07 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_gem.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_gem.h
> @@ -30,12 +30,6 @@ struct panfrost_gem_object {
> struct mutex lock;
> } mappings;
>
> - /*
> - * Count the number of jobs referencing this BO so we don't let the
> - * shrinker reclaim this object prematurely.
> - */
> - atomic_t gpu_usecount;
> -
> bool noexec :1;
> bool is_heap :1;
> };
> @@ -84,7 +78,4 @@ panfrost_gem_mapping_get(struct panfrost_gem_object *bo,
> void panfrost_gem_mapping_put(struct panfrost_gem_mapping *mapping);
> void panfrost_gem_teardown_mappings_locked(struct panfrost_gem_object *bo);
>
> -void panfrost_gem_shrinker_init(struct drm_device *dev);
> -void panfrost_gem_shrinker_cleanup(struct drm_device *dev);
> -
> #endif /* __PANFROST_GEM_H__ */
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
> deleted file mode 100644
> index 865a989d67c8..000000000000
> --- a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
> +++ /dev/null
> @@ -1,129 +0,0 @@
> -// SPDX-License-Identifier: GPL-2.0
> -/* Copyright (C) 2019 Arm Ltd.
> - *
> - * Based on msm_gem_freedreno.c:
> - * Copyright (C) 2016 Red Hat
> - * Author: Rob Clark <robdclark@xxxxxxxxx>
> - */
> -
> -#include <linux/list.h>
> -
> -#include <drm/drm_device.h>
> -#include <drm/drm_gem_shmem_helper.h>
> -
> -#include "panfrost_device.h"
> -#include "panfrost_gem.h"
> -#include "panfrost_mmu.h"
> -
> -static bool panfrost_gem_shmem_is_purgeable(struct drm_gem_shmem_object *shmem)
> -{
> - return (shmem->madv > 0) &&
> - !shmem->pages_pin_count && shmem->sgt &&
> - !shmem->base.dma_buf && !shmem->base.import_attach;
> -}
> -
> -static unsigned long
> -panfrost_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
> -{
> - struct panfrost_device *pfdev =
> - container_of(shrinker, struct panfrost_device, shrinker);
> - struct drm_gem_shmem_object *shmem;
> - unsigned long count = 0;
> -
> - if (!mutex_trylock(&pfdev->shrinker_lock))
> - return 0;
> -
> - list_for_each_entry(shmem, &pfdev->shrinker_list, madv_list) {
> - if (panfrost_gem_shmem_is_purgeable(shmem))
> - count += shmem->base.size >> PAGE_SHIFT;
> - }
> -
> - mutex_unlock(&pfdev->shrinker_lock);
> -
> - return count;
> -}
> -
> -static bool panfrost_gem_purge(struct drm_gem_object *obj)
> -{
> - struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
> - struct panfrost_gem_object *bo = to_panfrost_bo(obj);
> - bool ret = false;
> -
> - if (atomic_read(&bo->gpu_usecount))
> - return false;
> -
> - if (!mutex_trylock(&bo->mappings.lock))
> - return false;
> -
> - if (!dma_resv_trylock(shmem->base.resv))
> - goto unlock_mappings;
> -
> - panfrost_gem_teardown_mappings_locked(bo);
> - drm_gem_shmem_purge(&bo->base);
> - ret = true;
> -
> - dma_resv_unlock(shmem->base.resv);
> -
> -unlock_mappings:
> - mutex_unlock(&bo->mappings.lock);
> - return ret;
> -}
> -
> -static unsigned long
> -panfrost_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
> -{
> - struct panfrost_device *pfdev =
> - container_of(shrinker, struct panfrost_device, shrinker);
> - struct drm_gem_shmem_object *shmem, *tmp;
> - unsigned long freed = 0;
> -
> - if (!mutex_trylock(&pfdev->shrinker_lock))
> - return SHRINK_STOP;
> -
> - list_for_each_entry_safe(shmem, tmp, &pfdev->shrinker_list, madv_list) {
> - if (freed >= sc->nr_to_scan)
> - break;
> - if (drm_gem_shmem_is_purgeable(shmem) &&
> - panfrost_gem_purge(&shmem->base)) {
> - freed += shmem->base.size >> PAGE_SHIFT;
> - list_del_init(&shmem->madv_list);
> - }
> - }
> -
> - mutex_unlock(&pfdev->shrinker_lock);
> -
> - if (freed > 0)
> - pr_info_ratelimited("Purging %lu bytes\n", freed << PAGE_SHIFT);
> -
> - return freed;
> -}
> -
> -/**
> - * panfrost_gem_shrinker_init - Initialize panfrost shrinker
> - * @dev: DRM device
> - *
> - * This function registers and sets up the panfrost shrinker.
> - */
> -void panfrost_gem_shrinker_init(struct drm_device *dev)
> -{
> - struct panfrost_device *pfdev = dev->dev_private;
> - pfdev->shrinker.count_objects = panfrost_gem_shrinker_count;
> - pfdev->shrinker.scan_objects = panfrost_gem_shrinker_scan;
> - pfdev->shrinker.seeks = DEFAULT_SEEKS;
> - WARN_ON(register_shrinker(&pfdev->shrinker, "drm-panfrost"));
> -}
> -
> -/**
> - * panfrost_gem_shrinker_cleanup - Clean up panfrost shrinker
> - * @dev: DRM device
> - *
> - * This function unregisters the panfrost shrinker.
> - */
> -void panfrost_gem_shrinker_cleanup(struct drm_device *dev)
> -{
> - struct panfrost_device *pfdev = dev->dev_private;
> -
> - if (pfdev->shrinker.nr_deferred) {
> - unregister_shrinker(&pfdev->shrinker);
> - }
> -}
> diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
> index dbc597ab46fb..98d9751d2b2c 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_job.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_job.c
> @@ -272,6 +272,19 @@ static void panfrost_attach_object_fences(struct drm_gem_object **bos,
> dma_resv_add_fence(bos[i]->resv, fence, DMA_RESV_USAGE_WRITE);
> }
>
> +static int panfrost_objects_prepare(struct drm_gem_object **bos, int bo_count)
> +{
> + struct panfrost_gem_object *bo;
> + int ret = 0;
> +
> + while (!ret && bo_count--) {
> + bo = to_panfrost_bo(bos[bo_count]);
> + ret = bo->base.madv ? -ENOMEM : 0;
> + }
> +
> + return ret;
> +}
> +
> int panfrost_job_push(struct panfrost_job *job)
> {
> struct panfrost_device *pfdev = job->pfdev;
> @@ -283,6 +296,10 @@ int panfrost_job_push(struct panfrost_job *job)
> if (ret)
> return ret;
>
> + ret = panfrost_objects_prepare(job->bos, job->bo_count);
> + if (ret)
> + goto unlock;
> +
> mutex_lock(&pfdev->sched_lock);
> drm_sched_job_arm(&job->base);
>
> @@ -324,7 +341,6 @@ static void panfrost_job_cleanup(struct kref *ref)
> if (!job->mappings[i])
> break;
>
> - atomic_dec(&job->mappings[i]->obj->gpu_usecount);
> panfrost_gem_mapping_put(job->mappings[i]);
> }
> kvfree(job->mappings);
