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fsverity: Remove WQ_UNBOUND from fsverity read workqueue
commitf959325e6a
upstream. WQ_UNBOUND causes significant scheduler latency on ARM64/Android. This is problematic for latency sensitive workloads, like I/O post-processing. Removing WQ_UNBOUND gives a 96% reduction in fsverity workqueue related scheduler latency and improves app cold startup times by ~30ms. WQ_UNBOUND was also removed from the dm-verity workqueue for the same reason [1]. This code was tested by running Android app startup benchmarks and measuring how long the fsverity workqueue spent in the runnable state. Before Total workqueue scheduler latency: 553800us After Total workqueue scheduler latency: 18962us [1]: https://lore.kernel.org/all/20230202012348.885402-1-nhuck@google.com/ Signed-off-by: Nathan Huckleberry <nhuck@google.com> Fixes:8a1d0f9cac
("fs-verity: add data verification hooks for ->readpages()") Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20230310193325.620493-1-nhuck@google.com Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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1 changed files with 6 additions and 6 deletions
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@ -259,15 +259,15 @@ EXPORT_SYMBOL_GPL(fsverity_enqueue_verify_work);
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int __init fsverity_init_workqueue(void)
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{
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/*
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* Use an unbound workqueue to allow bios to be verified in parallel
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* even when they happen to complete on the same CPU. This sacrifices
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* locality, but it's worthwhile since hashing is CPU-intensive.
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* Use a high-priority workqueue to prioritize verification work, which
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* blocks reads from completing, over regular application tasks.
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*
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* Also use a high-priority workqueue to prioritize verification work,
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* which blocks reads from completing, over regular application tasks.
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* For performance reasons, don't use an unbound workqueue. Using an
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* unbound workqueue for crypto operations causes excessive scheduler
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* latency on ARM64.
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*/
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fsverity_read_workqueue = alloc_workqueue("fsverity_read_queue",
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WQ_UNBOUND | WQ_HIGHPRI,
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WQ_HIGHPRI,
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num_online_cpus());
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if (!fsverity_read_workqueue)
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return -ENOMEM;
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