Tom Lane wrote: > Alvaro Herrera <[EMAIL PROTECTED]> writes: > > In light of this, may I ask whether it makes sense to compare the > > performance of two runs with similar shared_buffer settings? With > > O_DIRECT, I understand from this manpage that the OS is going to do > > little or no page caching, so shared_buffers should be increased to > > account for this fact. > > > Am I missing something? > > O_DIRECT is only being used for WAL page writes (or I sure hope so > anyway), so shared_buffers should be irrelevant.
Uh, O_DIRECT really just enables when open_sync is used, and I assume that is not used for writing dirty buffers during a checkpoint. -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073 ---------------------------(end of broadcast)--------------------------- TIP 4: Have you searched our list archives? http://archives.postgresql.org
