Re: [PATCH v2 2/2] swiotlb: checking whether swiotlb buffer is full with io_tlb_used

Konrad Rzeszutek Wilk
2019-01-17T15:25:31Z

On Mon, Dec 10, 2018 at 08:37:58AM +0800, Dongli Zhang wrote:
> This patch uses io_tlb_used to help check whether swiotlb buffer is full.
> io_tlb_used is no longer used for only debugfs. It is also used to help
> optimize swiotlb_tbl_map_single().

Please split this up.

That is have the 'if (unlikely(nslots > io_tlb_nslabs - io_tlb_used))'
as a seperate patch.

And the #ifdef folding in the previous patch.

Also rebase on top of latest Linus please.

>
> Suggested-by: Joe Jin <joe.jin@oracle.com>
> Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
> ---
> kernel/dma/swiotlb.c | 10 ++++------
> 1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index 3979c2c..9300341 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -76,12 +76,10 @@ static phys_addr_t io_tlb_start, io_tlb_end;
> */
> static unsigned long io_tlb_nslabs;
>
> -#ifdef CONFIG_DEBUG_FS
> /*
> * The number of used IO TLB block
> */
> static unsigned long io_tlb_used;
> -#endif
>
> /*
> * This is a free list describing the number of free entries available from
> @@ -489,6 +487,10 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
> * request and allocate a buffer from that IO TLB pool.
> */
> spin_lock_irqsave(&io_tlb_lock, flags);
> +
> + if (unlikely(nslots > io_tlb_nslabs - io_tlb_used))
> + goto not_found;
> +
> index = ALIGN(io_tlb_index, stride);
> if (index >= io_tlb_nslabs)
> index = 0;
> @@ -538,9 +540,7 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
> dev_warn(hwdev, "swiotlb buffer is full (sz: %zd bytes)\n", size);
> return SWIOTLB_MAP_ERROR;
> found:
> -#ifdef CONFIG_DEBUG_FS
> io_tlb_used += nslots;
> -#endif
> spin_unlock_irqrestore(&io_tlb_lock, flags);
>
> /*
> @@ -602,9 +602,7 @@ void swiotlb_tbl_unmap_single(struct device *hwdev, phys_addr_t tlb_addr,
> for (i = index - 1; (OFFSET(i, IO_TLB_SEGSIZE) != IO_TLB_SEGSIZE -1) && io_tlb_list[i]; i--)
> io_tlb_list[i] = ++count;
>
> -#ifdef CONFIG_DEBUG_FS
> io_tlb_used -= nslots;
> -#endif
> }
> spin_unlock_irqrestore(&io_tlb_lock, flags);
> }
> --
> 2.7.4
>