SELECT * FROM sys.dm_os_memory_clerks ORDER BY (single_pages_kb + multi_pages_kb + awe_allocated_kb) desc

We walk in the dark places no others will enter
We stand on the bridge and no one may pass

--find out how big buffer pool is and determine percentage used by each database

DECLARE @total_buffer INT;
SELECT @total_buffer = cntr_value   FROM sys.dm_os_performance_counters
WHERE RTRIM([object_name]) LIKE '%Buffer Manager'   AND counter_name = 'Total Pages';
;WITH src AS(   SELECT        database_id, db_buffer_pages = COUNT_BIG(*) 
FROM sys.dm_os_buffer_descriptors       --WHERE database_id BETWEEN 5 AND 32766       
GROUP BY database_id)SELECT   [db_name] = CASE [database_id] WHEN 32767        THEN 'Resource DB'        ELSE DB_NAME([database_id]) END,   db_buffer_pages,   db_buffer_MB = db_buffer_pages / 128,   db_buffer_percent = CONVERT(DECIMAL(6,3),        db_buffer_pages * 100.0 / @total_buffer)
FROM src
ORDER BY db_buffer_MB DESC;

--then drill down into memory used by objects in database of your choice

USE db_with_most_memory;

WITH src AS(   SELECT       [Object] = o.name,       [Type] = o.type_desc,       [Index] = COALESCE(i.name, ''),       [Index_Type] = i.type_desc,       p.[object_id],       p.index_id,       au.allocation_unit_id   
FROM       sys.partitions AS p   INNER JOIN       sys.allocation_units AS au       ON p.hobt_id = au.container_id   INNER JOIN       sys.objects AS o       ON p.[object_id] = o.[object_id]   INNER JOIN       sys.indexes AS i       ON o.[object_id] = i.[object_id]       AND p.index_id = i.index_id   WHERE       au.[type] IN (1,2,3)       AND o.is_ms_shipped = 0)
SELECT   src.[Object],   src.[Type],   src.[Index],   src.Index_Type,   buffer_pages = COUNT_BIG(b.page_id),   buffer_mb = COUNT_BIG(b.page_id) / 128
FROM   src
INNER JOIN   sys.dm_os_buffer_descriptors AS b  
 ON src.allocation_unit_id = b.allocation_unit_id
WHERE   b.database_id = DB_ID()
GROUP BY   src.[Object],   src.[Type],   src.[Index],   src.Index_Type
ORDER BY   buffer_pages DESC;