On 13 June 2014 14:10, Abhijit Menon-Sen <a...@2ndquadrant.com> wrote:
> nbtxlog.c:btree_xlog_vacuum() contains the following comment: > > * XXX we don't actually need to read the block, we just need to > * confirm it is unpinned. If we had a special call into the > * buffer manager we could optimise this so that if the block is > * not in shared_buffers we confirm it as unpinned. > > The attached patch introduces an XLogLockBlockRangeForCleanup() function > that addresses this, as well as a "special call into the buffer manager" > that makes it possible to lock the buffers without reading them. > In GetBufferWithoutRelcache(), I was wondering, rather than calling PinBuffer(), if we do this : LockBufHdr(buf); PinBuffer_Locked(buf); valid = ((buf->flags & BM_VALID) != 0); then we can avoid having the new buffer access strategy BAS_DISCARD that is introduced in this patch. And so the code changes in freelist.c would not be necessary. Will give further thought on the overall logic in XLogLockBlockRangeForCleanup(). > will follow up with some performance numbers soon. > Yes, that would be nice. -Amit
