Only allocate 2 bounce pages for maps that can only use them for buffers that
are unaligned on cache lines boundary, as we will never need more.
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Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=254229
@ -425,6 +425,8 @@ bus_dma_tag_create(bus_dma_tag_t parent, bus_size_t alignment,
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if (_bus_dma_can_bounce(newtag->lowaddr, newtag->highaddr)
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|| newtag->alignment > 1)
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newtag->flags |= BUS_DMA_COULD_BOUNCE;
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else
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maxsize = 2; /* Need at most 2 bounce pages for unaligned access on cache line boundaries */
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if ((flags & BUS_DMA_ALLOCNOW) != 0) {
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struct bounce_zone *bz;
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@ -519,7 +521,10 @@ static int allocate_bz_and_pages(bus_dma_tag_t dmat, bus_dmamap_t mapp)
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* Attempt to add pages to our pool on a per-instance
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* basis up to a sane limit.
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*/
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maxpages = MAX_BPAGES;
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if (dmat->flags & BUS_DMA_COULD_BOUNCE)
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maxpages = MAX_BPAGES;
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else
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maxpages = 2 * bz->map_count; /* Only need at most 2 pages for buffers unaligned on cache line boundaries */
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if ((dmat->flags & BUS_DMA_MIN_ALLOC_COMP) == 0
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|| (bz->map_count > 0 && bz->total_bpages < maxpages)) {
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int pages;
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