On 1/9/16 11:57 PM, Jinhua Luo wrote:
But I do not understand that why the process do so many IO with async commit? And it does not even happen at the shared buffer flushing and locks waiting. Where's the code path doing these IO?
I assume you're asking about all the IO to the heap table. That is most likely occurring as part of ReadBuffer(). As soon as you fill up shared buffers, BufferAlloc() is likely to end up with a dirty buffer, resulting in it calling FlushBuffer() (see src/backend/storage/buffer/bufmgr.c#1084).
Note that that call is tracked by TRACE_POSTGRESQL_BUFFER_WRITE_DIRTY_START(), so I'd expect you to see it in the relevant systemtap stats.
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