vfs: Fix multiple oversized downloaders when mounting with --vfs-read… #7719
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…-ahead When mounting with --vfs-read-ahead option, if a file is accessed at multiple offsets (for example, by a video player like Plex to read audio and video tracks) then each corresponding downloader would have the ReadAhead added to its offset, killing performance. This fix would shrink old downloaders and only keep the latest one with enhanced offset.
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I wanted to present if this fix makes any sense or if I am on the path to blow things up, if it does then I'll be happy to add any corresponding test and finish this PR. |
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What is the purpose of this change?
I was trying to mount my remote server using rclone and wanted to use
--vfs-read-aheadto smooth out files with variable bitrates. They typically average 60mb/s but can hit peaks of 120-150mb/s. However I observed having a large--vfs-read-aheadvalue (say4Gor8G) would often kill performance, especially when starting the stream from middle.When mounting with
--vfs-read-aheadoption, if a file is accessed at multiple offsets (for example, by a video player like Plex to read audio and video tracks) then each corresponding downloader would have theReadAheadadded to itsoffset, killing performance.This fix would shrink old downloaders and only keep the latest one with enhanced
offset.Was the change discussed in an issue or in the forum before?
I posted about the issue I was facing here: https://forum.rclone.org/t/plex-seeking-slow-until-it-reads-till-vfs-read-ahead/45346 but it gained no traction.
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