[6.18] bcache IO hinting updates #41
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…ack hints Add sysfs entries to support to hint for bypass/writeback by the ioprio assigned to the bio. If the bio is unassigned, use current's io-context ioprio for cache writeback or bypass (configured per-process with `ionice`). Having idle IOs bypass the cache can increase performance elsewhere since you probably don't care about their performance. In addition, this prevents idle IOs from promoting into (polluting) your cache and evicting blocks that are more important elsewhere. If you really nead the performance at the expense of SSD wearout, then configure ioprio_writeback and set your `ionice` appropriately. For example: echo 2,7 > /sys/block/bcache0/bcache/ioprio_bypass echo 2,0 > /sys/block/bcache0/bcache/ioprio_writeback See the documentation commit for details. v2: Removed calls to get_task_io_context() v3: bio_prio() macro has been deleted Co-authored-by: Eric Wheeler <bcache@linux.ewheeler.net> Signed-off-by: Eric Wheeler <bcache@linux.ewheeler.net> Acked-by: Kent Overstreet <kent.overstreet@gmail.com> Tested-by: Kai Krakow <kai@kaishome.de> Cc: nix@esperi.org.uk Signed-off-by: Kai Krakow <kai@kaishome.de>
v2: get_task_io_context() no longer exists in the kernel Signed-off-by: Eric Wheeler <bcache@linux.ewheeler.net> Signed-off-by: Kai Krakow <kai@kaishome.de>
Even if ioprio_bypass hints bypassing the request, we still allow it for REQ_META|REQ_PRIO bio. Cc: Eric Wheeler <bcache@linux.ewheeler.net> Signed-off-by: Kai Krakow <kai@kaishome.de>
It seems to queue a lot of work, and I've seen messages like this, suggesting to switch to WQ_UNBOUND: > kernel: workqueue: cache_lookup hogged CPU for >10000us 11 times, consider switching to WQ_UNBOUND Short observation shows, that this might also improve perceived desktop responsiveness. But this needs more testing. Signed-off-by: Kai Krakow <kai@kaishome.de>
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Added a commit to prevent the following message: Early perceived result is improved desktop responsiveness. |
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Export patch series: https://github.com/kakra/linux/pull/41.patch