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blk-mq: Fix wrong wakeup batch configuration which will cause hang
Commit180dccb0db
("blk-mq: fix tag_get wait task can't be awakened") will recalculate wake_batch when incrementing or decrementing active_queues to avoid wake_batch > hctx_max_depth. At the same time, in order to not affect performance as much as possible, the minimum wakeup batch is set to 4. But when the QD is small (such as QD=1), if inc or dec active_queues increases wakeup batch, that can lead to a hang: Fix this problem with the following strategies: QD : >= 32 | < 32 --------------------------------- wakeup batch: 8~4 | 3~1 Fixes:180dccb0db
("blk-mq: fix tag_get wait task can't be awakened") Link: https://lore.kernel.org/linux-block/78cafe94-a787-e006-8851-69906f0c2128@huawei.com/T/#t Reported-by: Alex Xu (Hello71) <alex_y_xu@yahoo.ca> Signed-off-by: Laibin Qiu <qiulaibin@huawei.com> Tested-by: Alex Xu (Hello71) <alex_y_xu@yahoo.ca> Link: https://lore.kernel.org/r/20220127100047.1763746-1-qiulaibin@huawei.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
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@ -488,9 +488,13 @@ void sbitmap_queue_recalculate_wake_batch(struct sbitmap_queue *sbq,
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unsigned int users)
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{
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unsigned int wake_batch;
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unsigned int min_batch;
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unsigned int depth = (sbq->sb.depth + users - 1) / users;
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wake_batch = clamp_val((sbq->sb.depth + users - 1) /
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users, 4, SBQ_WAKE_BATCH);
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min_batch = sbq->sb.depth >= (4 * SBQ_WAIT_QUEUES) ? 4 : 1;
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wake_batch = clamp_val(depth / SBQ_WAIT_QUEUES,
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min_batch, SBQ_WAKE_BATCH);
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__sbitmap_queue_update_wake_batch(sbq, wake_batch);
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}
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EXPORT_SYMBOL_GPL(sbitmap_queue_recalculate_wake_batch);
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