Commits on Mar 29, 2024

1. Speculative prefetch for reordered requests …

   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%).
   
   Signed-off-by:	Alexander Motin <mav@FreeBSD.org>
   Sponsored by:	iXsystems, Inc.

   

   amotin committed Mar 29, 2024
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