lkml.org 
[lkml]   [2019]   [Feb]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [RFC PATCH 01/31] mm: migrate: Add exchange_pages to exchange two lists of pages.
    On Fri, Feb 15, 2019 at 02:08:26PM -0800, Zi Yan wrote:
    > +struct page_flags {
    > + unsigned int page_error :1;
    > + unsigned int page_referenced:1;
    > + unsigned int page_uptodate:1;
    > + unsigned int page_active:1;
    > + unsigned int page_unevictable:1;
    > + unsigned int page_checked:1;
    > + unsigned int page_mappedtodisk:1;
    > + unsigned int page_dirty:1;
    > + unsigned int page_is_young:1;
    > + unsigned int page_is_idle:1;
    > + unsigned int page_swapcache:1;
    > + unsigned int page_writeback:1;
    > + unsigned int page_private:1;
    > + unsigned int __pad:3;
    > +};

    I'm not sure how to feel about this. It's a bit fragile versus somebody adding
    new page flags. I don't know whether it's needed or whether you can just
    copy page->flags directly because you're holding PageLock.

    > +static void exchange_page(char *to, char *from)
    > +{
    > + u64 tmp;
    > + int i;
    > +
    > + for (i = 0; i < PAGE_SIZE; i += sizeof(tmp)) {
    > + tmp = *((u64 *)(from + i));
    > + *((u64 *)(from + i)) = *((u64 *)(to + i));
    > + *((u64 *)(to + i)) = tmp;
    > + }
    > +}

    I have a suspicion you'd be better off allocating a temporary page and
    using copy_page(). Some architectures have put a lot of effort into
    making copy_page() run faster.

    > + xa_lock_irq(&to_mapping->i_pages);
    > +
    > + to_pslot = radix_tree_lookup_slot(&to_mapping->i_pages,
    > + page_index(to_page));

    This needs to be converted to the XArray. radix_tree_lookup_slot() is
    going away soon. You probably need:

    XA_STATE(to_xas, &to_mapping->i_pages, page_index(to_page));

    This is a lot of code and I'm still trying to get my head aroud it all.
    Thanks for putting in this work; it's good to see this approach being
    explored.

    \
     
     \ /
      Last update: 2019-02-17 12:31    [W:4.456 / U:0.124 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site