Review the fields of __wt_page and __wt_evict, there are some fields that can be smaller types to reduce the memory usage, especially in __wt_page field, because we have millions of pages in some cases.
e.g.:
uint32_t entries; /* Leaf page entries */

uint32_tprefix_start; /* Best page prefix starting slot */
uint32_tprefix_stop; /* Maximum slot to which the best page prefix applies */

Also, we need to review and arrange the correct order for structure padding alignment requirements,
e.g.:

uint32_tevict_tune_num_points; /* Number of values tried */
uint64_tevict_tune_progress_last; /* Progress counter */
uint64_tevict_tune_progress_rate_max; /* Max progress rate */
boolevict_tune_stable; /* Are we stable? */
uint32_tevict_tune_workers_best; /* Best performing value */

We should either use a flag or put this together with other bool variables.