Alexander Motin 70ea484e3e Finally drop long disabled vdev cache. ... It was a vdev level read cache, designed to aggregate many small reads by speculatively issuing bigger reads instead and caching the result. But since it has almost no idea about what is going on with exception of ZIO_FLAG_DONT_CACHE flag set by higher layers, it was found to make more harm than good, for which reason it was disabled for the past 12 years. These days we have much better instruments to enlarge the I/Os, such as speculative and prescient prefetches, I/O scheduler, I/O aggregation etc. Besides just the dead code removal this removes one extra mutex lock/unlock per write inside vdev_cache_write(), not otherwise disabled and trying to do some work. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Alexander Motin <mav@FreeBSD.org> Sponsored by: iXsystems, Inc. Closes #14953		2023-06-09 12:40:55 -07:00
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linux	Finally drop long disabled vdev cache.	2023-06-09 12:40:55 -07:00