Greg Smith <[EMAIL PROTECTED]> wrote: > > In my understanding, each backend pins two or so buffers at once. So > > percentage of pinned buffers should be low. > > With the pgbench workload, a substantial percentage of the buffer cache > ends up pinned.
> http://westnet.com/~gsmith/content/postgresql/new-patch-checkpoint.txt > bgwriter scan all writes=16.6 MB (69.3%) pinned=11.7 MB (48.8%) LRU=7.7 MB > (31.9%) > ... > checkpoint required (wrote checkpoint_segments) > checkpoint buffers dirty=19.4 MB (80.8%) write=188.9 ms sync=4918.1 ms > > Here 69% of the buffer cache contained dirty data, and 49% of the cache > was both pinned and dirty. No. "Pinned" means bufHdr->refcount > 0 and you don't distinguish pinned or recently-used (bufHdr->usage_count > 0) buffers in your patch. ! if (bufHdr->refcount != 0 || bufHdr->usage_count != 0) { ! if (skip_pinned) ! { ! UnlockBufHdr(bufHdr); ! return BUF_PINNED; ! } ! buffer_write_type=BUF_WRITTEN_AND_PINNED; Regards, --- ITAGAKI Takahiro NTT Open Source Software Center ---------------------------(end of broadcast)--------------------------- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
