Force pages to split in the case of lots of small updates on a page

--- a/src/include/reconcile.i

+++ b/src/include/reconcile.i

@@ -197,6 +197,21 @@ __rec_page_time_stats(WT_SESSION_IMPL *session, WT_RECONCILE *r)

 static inline bool

 __wt_rec_need_split(WT_RECONCILE *r, size_t len)

 {

+    /*

+     * In the case of a row-store leaf page, trigger a split if a threshold number of saved updates

+     * is reached. This allows pages to split for update/restore and history store eviction when

+     * there is no visible data causing the disk image to grow.

+     *

+     * In the case of small pages or large keys, we might try to split when a page has no updates or

+     * entries, which isn't possible. To consider update/restore or history store information,

+     * require either page entries or updates that will be attached to the image. The limit is one

+     * of either, but it doesn't make sense to create pages or images with few entries or updates,

+     * even where page sizes are small (especially as updates that will eventually become overflow

+     * items can throw off our calculations). Bound the combination at something reasonable.

+     */

+    if (r->page->type == WT_PAGE_ROW_LEAF && r->entries + r->supd_next > 10)

+        len += r->supd_memsize / 10;

+

     /* Check for the disk image crossing a boundary. */

     return (WT_CHECK_CROSSING_BND(r, len));

 }