On Tue, Sep 29, 2020 at 9:46 PM Chris Goldsworthy
<cgoldswo@xxxxxxxxxxxxxx> wrote:
>
> On 2020-09-25 21:24, John Stultz wrote:
> > Reuse/abuse the pagepool code from the network code to speed
> > up allocation performance.
> >
> > This is similar to the ION pagepool usage, but tries to
> > utilize generic code instead of a custom implementation.
> >
> > Cc: Sumit Semwal <sumit.semwal@xxxxxxxxxx>
> > Cc: Liam Mark <lmark@xxxxxxxxxxxxxx>
> > Cc: Laura Abbott <labbott@xxxxxxxxxx>
> > Cc: Brian Starkey <Brian.Starkey@xxxxxxx>
> > Cc: Hridya Valsaraju <hridya@xxxxxxxxxx>
> > Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> > Cc: Sandeep Patil <sspatil@xxxxxxxxxx>
> > Cc: Ørjan Eide <orjan.eide@xxxxxxx>
> > Cc: Robin Murphy <robin.murphy@xxxxxxx>
> > Cc: Ezequiel Garcia <ezequiel@xxxxxxxxxxxxx>
> > Cc: Simon Ser <contact@xxxxxxxxxxx>
> > Cc: James Jones <jajones@xxxxxxxxxx>
> > Cc: linux-media@xxxxxxxxxxxxxxx
> > Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> > Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
> > ---
> > drivers/dma-buf/heaps/Kconfig | 1 +
> > drivers/dma-buf/heaps/system_heap.c | 32 +++++++++++++++++++++++++----
> > 2 files changed, 29 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/dma-buf/heaps/Kconfig
> > b/drivers/dma-buf/heaps/Kconfig
> > index a5eef06c4226..f13cde4321b1 100644
> > --- a/drivers/dma-buf/heaps/Kconfig
> > +++ b/drivers/dma-buf/heaps/Kconfig
> > @@ -1,6 +1,7 @@
> > config DMABUF_HEAPS_SYSTEM
> > bool "DMA-BUF System Heap"
> > depends on DMABUF_HEAPS
> > + select PAGE_POOL
> > help
> > Choose this option to enable the system dmabuf heap. The system
> > heap
> > is backed by pages from the buddy allocator. If in doubt, say Y.
> > diff --git a/drivers/dma-buf/heaps/system_heap.c
> > b/drivers/dma-buf/heaps/system_heap.c
> > index 882a632e9bb7..9f57b4c8ae69 100644
> > --- a/drivers/dma-buf/heaps/system_heap.c
> > +++ b/drivers/dma-buf/heaps/system_heap.c
> > @@ -20,6 +20,7 @@
> > #include <linux/scatterlist.h>
> > #include <linux/slab.h>
> > #include <linux/vmalloc.h>
> > +#include <net/page_pool.h>
> >
> > struct dma_heap *sys_heap;
> >
> > @@ -46,6 +47,7 @@ struct dma_heap_attachment {
> > static gfp_t order_flags[] = {HIGH_ORDER_GFP, LOW_ORDER_GFP,
> > LOW_ORDER_GFP};
> > static const unsigned int orders[] = {8, 4, 0};
> > #define NUM_ORDERS ARRAY_SIZE(orders)
> > +struct page_pool *pools[NUM_ORDERS];
> >
> > static struct sg_table *dup_sg_table(struct sg_table *table)
> > {
> > @@ -264,13 +266,17 @@ static void system_heap_dma_buf_release(struct
> > dma_buf *dmabuf)
> > struct system_heap_buffer *buffer = dmabuf->priv;
> > struct sg_table *table;
> > struct scatterlist *sg;
> > - int i;
> > + int i, j;
> >
> > table = &buffer->sg_table;
> > for_each_sg(table->sgl, sg, table->nents, i) {
> > struct page *page = sg_page(sg);
> >
> > - __free_pages(page, compound_order(page));
> > + for (j = 0; j < NUM_ORDERS; j++) {
> > + if (compound_order(page) == orders[j])
> > + break;
> > + }
> > + page_pool_put_full_page(pools[j], page, false);
> > }
> > sg_free_table(table);
> > kfree(buffer);
> > @@ -300,8 +306,7 @@ static struct page
> > *alloc_largest_available(unsigned long size,
> > continue;
> > if (max_order < orders[i])
> > continue;
> > -
> > - page = alloc_pages(order_flags[i], orders[i]);
> > + page = page_pool_alloc_pages(pools[i], order_flags[i]);
> > if (!page)
> > continue;
> > return page;
> > @@ -406,6 +411,25 @@ static const struct dma_heap_ops system_heap_ops =
> > {
> > static int system_heap_create(void)
> > {
> > struct dma_heap_export_info exp_info;
> > + int i;
> > +
> > + for (i = 0; i < NUM_ORDERS; i++) {
> > + struct page_pool_params pp;
> > +
> > + memset(&pp, 0, sizeof(pp));
> > + pp.order = orders[i];
> > + pp.dma_dir = DMA_BIDIRECTIONAL;
> > + pools[i] = page_pool_create(&pp);
> > +
> > + if (IS_ERR(pools[i])) {
> > + int j;
> > +
> > + pr_err("%s: page pool creation failed!\n", __func__);
> > + for (j = 0; j < i; j++)
> > + page_pool_destroy(pools[j]);
> > + return PTR_ERR(pools[i]);
> > + }
> > + }
> >
> > exp_info.name = "system";
> > exp_info.ops = &system_heap_ops;
>
> This is cool, I didn't know about this pooling code under /net/core.
> Nice and compact.
Oh, bummer. I just realized when allocating w/ __GFP_ZERO from the
page-pool, the logic doesn't actually clear pages when pulling from
the cache.
So unfortunately this is what accounts for much of the performance
benefit I was seeing with this approach, so I'll have to retract my
claim on the performance gain with this. :(
I've got a first pass at zeroing the pages we put into the pool, but
the numbers are not so great just yet so I've got some further work to
do.
thanks
-john
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