Hi Laurent,
On 06/04/18 23:55, Laurent Pinchart wrote:
> Hi Kieran,
>
> Thank you for the patch.
>
> On Thursday, 8 March 2018 02:05:27 EEST Kieran Bingham wrote:
>> Adapt the dl->body0 object to use an object from the body pool. This
>> greatly reduces the pressure on the TLB for IPMMU use cases, as all of
>> the lists use a single allocation for the main body.
>>
>> The CLU and LUT objects pre-allocate a pool containing three bodies,
>> allowing a userspace update before the hardware has committed a previous
>> set of tables.
>>
>> Bodies are no longer 'freed' in interrupt context, but instead released
>> back to their respective pools. This allows us to remove the garbage
>> collector in the DLM.
>>
>> Signed-off-by: Kieran Bingham <kieran.bingham+rene...@ideasonboard.com>
>>
>> ---
>> v3:
>> - 's/fragment/body', 's/fragments/bodies/'
>> - CLU/LUT now allocate 3 bodies
>> - vsp1_dl_list_fragments_free -> vsp1_dl_list_bodies_put
>>
>> v2:
>> - Use dl->body0->max_entries to determine header offset, instead of the
>> global constant VSP1_DL_NUM_ENTRIES which is incorrect.
>> - squash updates for LUT, CLU, and fragment cleanup into single patch.
>> (Not fully bisectable when separated)
>>
>> drivers/media/platform/vsp1/vsp1_clu.c | 27 ++-
>> drivers/media/platform/vsp1/vsp1_clu.h | 1 +-
>> drivers/media/platform/vsp1/vsp1_dl.c | 223 ++++++--------------------
>> drivers/media/platform/vsp1/vsp1_dl.h | 3 +-
>> drivers/media/platform/vsp1/vsp1_lut.c | 27 ++-
>> drivers/media/platform/vsp1/vsp1_lut.h | 1 +-
>> 6 files changed, 101 insertions(+), 181 deletions(-)
>
> Still a nice diffstart :-)
>
> [snip]
>
>> diff --git a/drivers/media/platform/vsp1/vsp1_dl.c
>> b/drivers/media/platform/vsp1/vsp1_dl.c index 0208e72cb356..74476726451c
>> 100644
>> --- a/drivers/media/platform/vsp1/vsp1_dl.c
>> +++ b/drivers/media/platform/vsp1/vsp1_dl.c
>
> [snip]
>
>> @@ -399,11 +311,10 @@ void vsp1_dl_body_write(struct vsp1_dl_body *dlb, u32
>> reg, u32 data) * Display List Transaction Management
>> */
>>
>> -static struct vsp1_dl_list *vsp1_dl_list_alloc(struct vsp1_dl_manager *dlm)
>> +static struct vsp1_dl_list *vsp1_dl_list_alloc(struct vsp1_dl_manager
>> *dlm,
>> + struct vsp1_dl_body_pool *pool)
>
> Given that the only caller of this function passes dlm->pool as the second
> argument, can't you remove the second argument ?
Hrm ... I thought there was going to be a use case where the pool will be
separated. But perhaps not.
So yes - Removing.
>
>> {
>> struct vsp1_dl_list *dl;
>> - size_t header_size;
>> - int ret;
>>
>> dl = kzalloc(sizeof(*dl), GFP_KERNEL);
>> if (!dl)
>> @@ -412,41 +323,39 @@ static struct vsp1_dl_list *vsp1_dl_list_alloc(struct
>> vsp1_dl_manager *dlm) INIT_LIST_HEAD(&dl->bodies);
>> dl->dlm = dlm;
>>
>> - /*
>> - * Initialize the display list body and allocate DMA memory for the body
>> - * and the optional header. Both are allocated together to avoid memory
>> - * fragmentation, with the header located right after the body in
>> - * memory.
>> - */
>> - header_size = dlm->mode == VSP1_DL_MODE_HEADER
>> - ? ALIGN(sizeof(struct vsp1_dl_header), 8)
>> - : 0;
>> -
>> - ret = vsp1_dl_body_init(dlm->vsp1, &dl->body0, VSP1_DL_NUM_ENTRIES,
>> - header_size);
>> - if (ret < 0) {
>> - kfree(dl);
>> + /* Retrieve a body from our DLM body pool */
>
> s/body pool/body pool./
>
> (And I would have said "Get a body" but that's up to you)
I think that's evident by the function name "vsp1_dl_body_get()", thus I've
adapted this comment to be a bit more meaningful:
/* Get a default body for our list. */
But I'm not opposed to dropping the comment. Also at somepoint, I think there's
scope to remove the dl->body0 so it may not matter.
>
>> + dl->body0 = vsp1_dl_body_get(pool);
>> + if (!dl->body0)
>> return NULL;
>> - }
>> -
>> if (dlm->mode == VSP1_DL_MODE_HEADER) {
>> - size_t header_offset = VSP1_DL_NUM_ENTRIES
>> - * sizeof(*dl->body0.entries);
>> + size_t header_offset = dl->body0->max_entries
>> + * sizeof(*dl->body0->entries);
>>
>> - dl->header = ((void *)dl->body0.entries) + header_offset;
>> - dl->dma = dl->body0.dma + header_offset;
>> + dl->header = ((void *)dl->body0->entries) + header_offset;
>> + dl->dma = dl->body0->dma + header_offset;
>>
>> memset(dl->header, 0, sizeof(*dl->header));
>> - dl->header->lists[0].addr = dl->body0.dma;
>> + dl->header->lists[0].addr = dl->body0->dma;
>> }
>>
>> return dl;
>> }
>>
>> +static void vsp1_dl_list_bodies_put(struct vsp1_dl_list *dl)
>> +{
>> + struct vsp1_dl_body *dlb, *tmp;
>> +
>> + list_for_each_entry_safe(dlb, tmp, &dl->bodies, list) {
>> + list_del(&dlb->list);
>> + vsp1_dl_body_put(dlb);
>> + }
>> +}
>> +
>> static void vsp1_dl_list_free(struct vsp1_dl_list *dl)
>> {
>> - vsp1_dl_body_cleanup(&dl->body0);
>> - list_splice_init(&dl->bodies, &dl->dlm->gc_bodies);
>> + vsp1_dl_body_put(dl->body0);
>> + vsp1_dl_list_bodies_put(dl);
>
> Too bad we can't keep the list splice, it's more efficient than iterating
> over
> the list, but I suppose it's unavoidable if we want to reset the number of
> used entries to 0 for each body. Beside, we should have a small number of
> bodies only, so hopefully it won't be a big deal.
Yes, plus reference counting needs to be tracked too ... so I think we need to
keep this.
>
>> +
>> kfree(dl);
>> }
>>
>> @@ -500,18 +409,13 @@ static void __vsp1_dl_list_put(struct vsp1_dl_list
>> *dl)
>>
>> dl->has_chain = false;
>>
>> + vsp1_dl_list_bodies_put(dl);
>> +
>> /*
>> - * We can't free bodies here as DMA memory can only be freed in
>> - * interruptible context. Move all bodies to the display list manager's
>> - * list of bodies to be freed, they will be garbage-collected by the
>> - * work queue.
>> + * body0 is reused as as an optimisation as presently every display list
>> + * has at least one body, thus we reinitialise the entries list
>
> s/entries list/entries list./
Done
>
>> */
>> - if (!list_empty(&dl->bodies)) {
>> - list_splice_init(&dl->bodies, &dl->dlm->gc_bodies);
>> - schedule_work(&dl->dlm->gc_work);
>> - }
>
> We can certainly do this synchronously now that we don't need to free memory
> anymore. I wonder however about the potential performance impact, as there's
> a
> kfree() in vsp1_dl_list_free().
Yes, but ...
> Do you think it could have a noticeable impact on the time spent with
> interrupts disabled ?
I doubt it ... vsp1_dl_list_free() is only called from vsp1_dlm_destroy(), which
is only called from vsp1_wpf_destroy().
That's the whole benefit of being able to remove the garbage collector.
>> -
>> - dl->body0.num_entries = 0;
>> + dl->body0->num_entries = 0;
>>
>> list_add_tail(&dl->list, &dl->dlm->free);
>> }
>> @@ -548,7 +452,7 @@ void vsp1_dl_list_put(struct vsp1_dl_list *dl)
>> */
>> void vsp1_dl_list_write(struct vsp1_dl_list *dl, u32 reg, u32 data)
>> {
>> - vsp1_dl_body_write(&dl->body0, reg, data);
>> + vsp1_dl_body_write(dl->body0, reg, data);
>> }
>>
>> /**
>> @@ -561,8 +465,7 @@ void vsp1_dl_list_write(struct vsp1_dl_list *dl, u32
>> reg, u32 data)
>> * in the order in which bodies are added.
>> *
>> * Adding a body to a display list passes ownership of the body to the
>> list. The
>> - * caller must not touch the body after this call, and must not free it
>> - * explicitly with vsp1_dl_body_free().
>
> Shouldn't we keep the last part of the sentence and adapt it ? Maybe
> something
> like
>
> and must not release it explicitly with vsp1_dl_body_put().
>
> I know that you introduce a reference count in the next patches that would
> make this comment invalid, up to this patch it should be correct. When
> introducing reference-counting you can update the comment to state that the
> reference must be released.
>
Sure ... It's a very temporary statement :-)
>> + * caller must not touch the body after this call.
>> *
>> * Additional bodies are only usable for display lists in header mode.
>> * Attempting to add a body to a header-less display list will return an
>> error. @@ -620,7 +523,7 @@ static void vsp1_dl_list_fill_header(struct
>> vsp1_dl_list *dl, bool is_last)
>> * list was allocated.
>> */
>>
>> - hdr->num_bytes = dl->body0.num_entries
>> + hdr->num_bytes = dl->body0->num_entries
>> * sizeof(*dl->header->lists);
>>
>> list_for_each_entry(dlb, &dl->bodies, list) {
>> @@ -694,9 +597,9 @@ static void vsp1_dl_list_hw_enqueue(struct vsp1_dl_list
>> *dl) * bit will be cleared by the hardware when the display list
>> * processing starts.
>> */
>> - vsp1_write(vsp1, VI6_DL_HDR_ADDR(0), dl->body0.dma);
>> + vsp1_write(vsp1, VI6_DL_HDR_ADDR(0), dl->body0->dma);
>> vsp1_write(vsp1, VI6_DL_BODY_SIZE, VI6_DL_BODY_SIZE_UPD |
>> - (dl->body0.num_entries *
>> sizeof(*dl->header->lists)));
>> + (dl->body0->num_entries * sizeof(*dl->header->lists)));
>> } else {
>> /*
>> * In header mode, program the display list header address. If
>> @@ -879,45 +782,12 @@ void vsp1_dlm_reset(struct vsp1_dl_manager *dlm)
>> dlm->pending = NULL;
>> }
>>
>> -/*
>> - * Free all bodies awaiting to be garbage-collected.
>> - *
>> - * This function must be called without the display list manager lock held.
>> - */
>> -static void vsp1_dlm_bodies_free(struct vsp1_dl_manager *dlm)
>> -{
>> - unsigned long flags;
>> -
>> - spin_lock_irqsave(&dlm->lock, flags);
>> -
>> - while (!list_empty(&dlm->gc_bodies)) {
>> - struct vsp1_dl_body *dlb;
>> -
>> - dlb = list_first_entry(&dlm->gc_bodies, struct vsp1_dl_body,
>> - list);
>> - list_del(&dlb->list);
>> -
>> - spin_unlock_irqrestore(&dlm->lock, flags);
>> - vsp1_dl_body_free(dlb);
>> - spin_lock_irqsave(&dlm->lock, flags);
>> - }
>> -
>> - spin_unlock_irqrestore(&dlm->lock, flags);
>> -}
>> -
>> -static void vsp1_dlm_garbage_collect(struct work_struct *work)
>> -{
>> - struct vsp1_dl_manager *dlm =
>> - container_of(work, struct vsp1_dl_manager, gc_work);
>> -
>> - vsp1_dlm_bodies_free(dlm);
>> -}
>> -
>> struct vsp1_dl_manager *vsp1_dlm_create(struct vsp1_device *vsp1,
>> unsigned int index,
>> unsigned int prealloc)
>> {
>> struct vsp1_dl_manager *dlm;
>> + size_t header_size;
>> unsigned int i;
>>
>> dlm = devm_kzalloc(vsp1->dev, sizeof(*dlm), GFP_KERNEL);
>> @@ -932,13 +802,26 @@ struct vsp1_dl_manager *vsp1_dlm_create(struct
>> vsp1_device *vsp1,
>>
>> spin_lock_init(&dlm->lock);
>> INIT_LIST_HEAD(&dlm->free);
>> - INIT_LIST_HEAD(&dlm->gc_bodies);
>> - INIT_WORK(&dlm->gc_work, vsp1_dlm_garbage_collect);
>> +
>> + /*
>> + * Initialize the display list body and allocate DMA memory for the body
>> + * and the optional header. Both are allocated together to avoid memory
>> + * fragmentation, with the header located right after the body in
>> + * memory.
>> + */
>> + header_size = dlm->mode == VSP1_DL_MODE_HEADER
>> + ? ALIGN(sizeof(struct vsp1_dl_header), 8)
>> + : 0;
>> +
>> + dlm->pool = vsp1_dl_body_pool_create(vsp1, prealloc,
>> + VSP1_DL_NUM_ENTRIES, header_size);
>> + if (!dlm->pool)
>> + return NULL;
>>
>> for (i = 0; i < prealloc; ++i) {
>> struct vsp1_dl_list *dl;
>>
>> - dl = vsp1_dl_list_alloc(dlm);
>> + dl = vsp1_dl_list_alloc(dlm, dlm->pool);
>> if (!dl)
>> return NULL;
>>
>> @@ -955,12 +838,10 @@ void vsp1_dlm_destroy(struct vsp1_dl_manager *dlm)
>> if (!dlm)
>> return;
>>
>> - cancel_work_sync(&dlm->gc_work);
>> -
>> list_for_each_entry_safe(dl, next, &dlm->free, list) {
>> list_del(&dl->list);
>> vsp1_dl_list_free(dl);
>> }
>>
>> - vsp1_dlm_bodies_free(dlm);
>> + vsp1_dl_body_pool_destroy(dlm->pool);
>> }
>
> [snip]
>
