5e5fd0a178
Before this change speculative prefetcher was able to detect a stream only if all of its accesses are perfectly sequential. It was easy to implement and is perfectly fine for single-threaded applications. Unfortunately multi-threaded network servers, such as iSCSI, SMB or NFS usually have plenty of threads and may often reorder requests, preventing successful speculation and prefetch. This change allows speculative prefetcher to detect streams even if requests are reordered by introducing a list of 9 non-contiguous ranges up to 16MB ahead of current stream position and filling the gaps as more requests arrive. It also allows stream to proceed even with holes up to a certain configurable threshold (25%). Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Alexander Motin <mav@FreeBSD.org> Sponsored by: iXsystems, Inc. Closes #16022 |
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