The present Linux implementation doesn't do this, AFAICS -- all it doesAFAIK Linux uses a modified LRU that automatically puts pages that were touched only once at a lower priority than frequently accessed pages.
it increase the readahead for this file:
Neil: what about calling posix_fadvise for the whole file immediately after issue_xlog_fsync() in XLogWrite? According to the comment, it's guaranteed that this will happen only once.
Or: add an posix_fadvise into issue_xlog_fsync(), for the range just sync'ed.
Btw, how much xlog traffic does a busy postgres site generate?
-- Manfred
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