On 2/23/22 03:25, Andres Freund wrote: > Hi, > > On 2022-02-18 12:10:51 +1300, David Rowley wrote: >> The other way I thought to fix it was by changing the logic for when >> generation blocks are freed. In the problem case mentioned above, the >> block being freed is the current block (which was just allocated). I >> made some changes to adjust this behaviour so that we no longer free >> the block when the final chunk is pfree()'d. Instead, that now lingers >> and can be reused by future allocations, providing they fit inside it. > > That makes sense to me, as long as we keep just one such block. > > >> The problem I see with this method is that there still could be some >> pathological case that causes us to end up storing just a single tuple per >> generation block. > > Crazy idea: Detect the situation, and recompact. Create a new context, copy > all the tuples over, delete the old context. That could be a win even in less > adversarial situations than "a single tuple per generation block". >
What about pointers to the chunks in the old memory context? regards -- Tomas Vondra EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
