Re: Add pg_buffercache_mark_dirty[_all] functions to the pg_buffercache

I noticed a couple of small clarity issues in the current version of patch for potential clean up:

1. Commit message wording

Right now it says:

“The pg_buffercache_mark_dirty_all() function provides an efficient way to dirty the entire buffer pool (e.g., ~550 ms vs. ~70 ms for 16 GB of shared buffers), complementing pg_buffercache_mark_dirty() for more granular control.”

That makes it sound like the _all function is the granular one, when really:

• pg_buffercache_mark_dirty(buffernumber) is the fine-grained, per-buffer call.

• pg_buffercache_mark_dirty_all() is the bulk, coarse-grained operation.

How about rephrasing to:

“The pg_buffercache_mark_dirty_all() function provides an efficient, bulk way to mark every buffer dirty (e.g., ~70 ms vs. ~550 ms for 16 GB of shared buffers), while pg_buffercache_mark_dirty() still allows per-buffer, granular control.”

2. Inline comment in MarkUnpinnedBufferDirty

We currently have:

PinBuffer_Locked(desc);  /* releases spinlock */

Folks who’re unfamiliar with this function might get confused. Maybe we could use the one in GetVictimBuffer:

/* Pin the buffer and then release its spinlock */

PinBuffer_Locked(buf_hdr);

That spelling-out makes it obvious what’s happening.