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    Subject[PATCH 07/19] vmw_balloon: treat all refused pages equally
    Date
    Currently, when the hypervisor rejects a page during lock operation, the
    VM treats pages differently according to the error-code: in certain
    cases the page is immediately freed, and in others it is put on a
    rejection list and only freed later.

    The behavior does not make too much sense. If the page is freed
    immediately it is very likely to be used again in the next batch of
    allocations, and be rejected again.

    In addition, for support of compaction and OOM notifiers, we wish to
    separate the logic that communicates with the hypervisor (as well as
    analyzes the status of each page) from the logic that allocates or free
    pages.

    Treat all errors the same way, queuing the pages on the refuse list.
    Move to the next allocation size (4k) when too many pages are refused.
    Free the refused pages when moving to the next size to avoid situations
    in which too much memory is waiting to be freed on the refused list.

    Reviewed-by: Xavier Deguillard <xdeguillard@vmware.com>
    Signed-off-by: Nadav Amit <namit@vmware.com>
    ---
    drivers/misc/vmw_balloon.c | 52 +++++++++++++++++++++-----------------
    1 file changed, 29 insertions(+), 23 deletions(-)

    diff --git a/drivers/misc/vmw_balloon.c b/drivers/misc/vmw_balloon.c
    index e1b704d3d5cb..74fff1e314a7 100644
    --- a/drivers/misc/vmw_balloon.c
    +++ b/drivers/misc/vmw_balloon.c
    @@ -542,29 +542,13 @@ static int vmballoon_lock(struct vmballoon *b, unsigned int num_pages,
    /* Error occurred */
    STATS_INC(b->stats.refused_alloc[is_2m_pages]);

    - switch (status) {
    - case VMW_BALLOON_ERROR_PPN_PINNED:
    - case VMW_BALLOON_ERROR_PPN_INVALID:
    - /*
    - * Place page on the list of non-balloonable pages
    - * and retry allocation, unless we already accumulated
    - * too many of them, in which case take a breather.
    - */
    - if (page_size->n_refused_pages
    - < VMW_BALLOON_MAX_REFUSED) {
    - list_add(&p->lru, &page_size->refused_pages);
    - page_size->n_refused_pages++;
    - break;
    - }
    - /* Fallthrough */
    - case VMW_BALLOON_ERROR_RESET:
    - case VMW_BALLOON_ERROR_PPN_NOTNEEDED:
    - vmballoon_free_page(p, is_2m_pages);
    - break;
    - default:
    - /* This should never happen */
    - WARN_ON_ONCE(true);
    - }
    + /*
    + * Place page on the list of non-balloonable pages
    + * and retry allocation, unless we already accumulated
    + * too many of them, in which case take a breather.
    + */
    + list_add(&p->lru, &page_size->refused_pages);
    + page_size->n_refused_pages++;
    }

    return batch_status == VMW_BALLOON_SUCCESS ? 0 : -EIO;
    @@ -711,9 +695,31 @@ static void vmballoon_inflate(struct vmballoon *b)

    vmballoon_add_page(b, num_pages++, page);
    if (num_pages == b->batch_max_pages) {
    + struct vmballoon_page_size *page_size =
    + &b->page_sizes[is_2m_pages];
    +
    error = vmballoon_lock(b, num_pages, is_2m_pages);

    num_pages = 0;
    +
    + /*
    + * Stop allocating this page size if we already
    + * accumulated too many pages that the hypervisor
    + * refused.
    + */
    + if (page_size->n_refused_pages >=
    + VMW_BALLOON_MAX_REFUSED) {
    + if (!is_2m_pages)
    + break;
    +
    + /*
    + * Release the refused pages as we move to 4k
    + * pages.
    + */
    + vmballoon_release_refused_pages(b, true);
    + is_2m_pages = true;
    + }
    +
    if (error)
    break;
    }
    --
    2.17.1
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