04bae5ec95
High priority threads are handling ZIL writes. While there is no ZIL compression, there is encryption, checksuming and RAIDZ math. We've found that on large systems 1 taskq with 5 threads can be a bottleneck for throughput, IOPS or both. Instead of just bumping number of threads with a risk of overloading CPUs and increasing latency, switch to using TQ_FRONT mechanism to increase sync write requests priority within standard write threads. Do not do it on Illumos, since its TQ_FRONT implementation is inherently unfair. FreeBSD and Linux don't have this problem, so we can do it there. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Rob Norris <robn@despairlabs.com> Signed-off-by: Alexander Motin <mav@FreeBSD.org> Sponsored-By: iXsystems, Inc. Closes #16146 |
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