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    SubjectRe: [PATCH 03/13] scatterlist: Add sg_set_folio()
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    在 2023/7/31 5:42, Matthew Wilcox 写道:
    > On Sun, Jul 30, 2023 at 09:57:06PM +0800, Zhu Yanjun wrote:
    >> 在 2023/7/30 19:18, Matthew Wilcox 写道:
    >>> On Sun, Jul 30, 2023 at 07:01:26PM +0800, Zhu Yanjun wrote:
    >>>> Does the following function have folio version?
    >>>>
    >>>> "
    >>>> int sg_alloc_append_table_from_pages(struct sg_append_table *sgt_append,
    >>>> struct page **pages, unsigned int n_pages, unsigned int offset,
    >>>> unsigned long size, unsigned int max_segment,
    >>>> unsigned int left_pages, gfp_t gfp_mask)
    >>>> "
    >>> No -- I haven't needed to convert anything that uses
    >>> sg_alloc_append_table_from_pages() yet. It doesn't look like it should
    >>> be _too_ hard to add a folio version.
    >> In many places, this function is used. So this function needs the folio
    >> version.
    > It's not used in very many places. But the first one that I see it used
    > (drivers/infiniband/core/umem.c), you can't do a straightforward folio
    > conversion:
    >
    > pinned = pin_user_pages_fast(cur_base,
    > min_t(unsigned long, npages,
    > PAGE_SIZE /
    > sizeof(struct page *)),
    > gup_flags, page_list);
    > ...
    > ret = sg_alloc_append_table_from_pages(
    > &umem->sgt_append, page_list, pinned, 0,
    > pinned << PAGE_SHIFT, ib_dma_max_seg_size(device),
    > npages, GFP_KERNEL);
    >
    > That can't be converted to folios. The GUP might start in the middle of
    > the folio, and we have no way to communicate that.
    >
    > This particular usage really needs the phyr work that Jason is doing so
    > we can efficiently communicate physically contiguous ranges from GUP
    > to sg.

    Hi, Matthew

    Thanks. To the following function, it seems that no folio function
    replace vmalloc_to_page.

    vmalloc_to_page calls virt_to_page to get page. Finally the followings
    will be called.

    "
    (mem_map + ((pfn) - ARCH_PFN_OFFSET))

    "

    And I do not find the related folio functions with vmalloc_to_page.

    And no folio function replaces dma_map_page.

    dma_map_page will call dma_map_page_attrs.

    Or these 2 function should not be replaced with folio functions?

    int irdma_map_vm_page_list(struct irdma_hw *hw, void *va, dma_addr_t
    *pg_dma,

                               u32 pg_cnt)
    {
            struct page *vm_page;
            int i;
            u8 *addr;

            addr = (u8 *)(uintptr_t)va;
            for (i = 0; i < pg_cnt; i++) {
                    vm_page = vmalloc_to_page(addr);
                    if (!vm_page)
                            goto err;

                    pg_dma[i] = dma_map_page(hw->device, vm_page, 0, PAGE_SIZE,
                                             DMA_BIDIRECTIONAL);
                    if (dma_mapping_error(hw->device, pg_dma[i]))
                            goto err;

                    addr += PAGE_SIZE;
            }

            return 0;

    err:
            irdma_unmap_vm_page_list(hw, pg_dma, i);
            return -ENOMEM;

    }

    Thanks,

    Zhu Yanjun


    >> Another problem, after folio is used, I want to know the performance after
    >> folio is implemented.
    >>
    >> How to make tests to get the performance?
    > You know what you're working on ... I wouldn't know how best to test
    > your code.

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