The article kind of dances around it, but AIUI the reason that their "weite-only load" caused reads (and thus readahead) was because they were writing to a mapped page that had already been evicted - so the kernel was reading/faulting those pages because it can only write in block/page sized chunks.
In some sense maybe this could be thought of as readahead in preparation for writing to those pages, which is undesirable in this case.
However, what confused be about this article was if the data files are append only, how is there a "next" block to read ahead to? I guess maybe the files are pre-allocated or the kernel is reading previous pages.
In some sense maybe this could be thought of as readahead in preparation for writing to those pages, which is undesirable in this case.
However, what confused be about this article was if the data files are append only, how is there a "next" block to read ahead to? I guess maybe the files are pre-allocated or the kernel is reading previous pages.