lkml.org 
[lkml]   [2022]   [Nov]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 1/3] mm,hugetlb: use folio fields in second tail page
    On Thu, 3 Nov 2022, Sidhartha Kumar wrote:
    > On 11/2/22 6:48 PM, Hugh Dickins wrote:
    ...
    > > Undo "mm: add private field of first tail to struct page and struct
    > > folio"'s recent addition of private_1 to the folio tail: instead add
    > > hugetlb_subpool, hugetlb_cgroup, hugetlb_cgroup_rsvd, hugetlb_hwpoison
    > > to a second tail page of the folio: THP has long been using several
    > > fields of that tail, so make better use of it for hugetlb too.
    > > This is not how a generic folio should be declared in future,
    > > but it is an effective transitional way to make use of it.
    ...
    > > @@ -260,13 +267,16 @@ struct page {
    > > * to find how many references there are to this folio.
    > > * @memcg_data: Memory Control Group data.
    > > * @_flags_1: For large folios, additional page flags.
    > > - * @__head: Points to the folio. Do not use.
    > > + * @_head_1: Points to the folio. Do not use.
    >
    > Changes to my original patch set look good, this seems to be a cleaner
    > implementation.

    Thanks a lot, Sidhartha, I'm glad to hear that it works for you too.

    I expect that it will be done differently in the future: maybe generalizing
    the additional fields to further "private"s as you did, letting different
    subsystems accessorize them differently; or removing them completely from
    struct folio, letting subsystems declare their own struct folio containers.
    I don't know how that will end up, but this for now seems good and clear.

    >
    > Should the usage of page_1 and page_2 also be documented here?

    You must have something interesting in mind to document about them,
    but I cannot guess what! They are for field alignment, not for use.
    (page_2 to help when/if someone needs to add another pageful.)

    Do you mean that I should copy the
    /* private: the union with struct page is transitional */
    comment from above the original "struct page page;" line I copied?
    Or give all three of them a few underscores to imply not for use?

    Thanks,
    Hugh

    \
     
     \ /
      Last update: 2022-11-04 05:30    [W:2.558 / U:0.032 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site