block: rename CONFIG_DEBUG_BLK_CGROUP to CONFIG_BFQ_CGROUP_DEBUG
This option is entirely bfq specific, give it an appropinquate name. Also make it depend on CONFIG_BFQ_GROUP_IOSCHED in Kconfig, as all the functionality already does so anyway. Acked-by: Tejun Heo <tj@kernel.org> Acked-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Jens Axboe

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@@ -38,13 +38,13 @@ stack). To give an idea of the limits with BFQ, on slow or average
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CPUs, here are, first, the limits of BFQ for three different CPUs, on,
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respectively, an average laptop, an old desktop, and a cheap embedded
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system, in case full hierarchical support is enabled (i.e.,
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CONFIG_BFQ_GROUP_IOSCHED is set), but CONFIG_DEBUG_BLK_CGROUP is not
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CONFIG_BFQ_GROUP_IOSCHED is set), but CONFIG_BFQ_CGROUP_DEBUG is not
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set (Section 4-2):
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- Intel i7-4850HQ: 400 KIOPS
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- AMD A8-3850: 250 KIOPS
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- ARM CortexTM-A53 Octa-core: 80 KIOPS
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If CONFIG_DEBUG_BLK_CGROUP is set (and of course full hierarchical
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If CONFIG_BFQ_CGROUP_DEBUG is set (and of course full hierarchical
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support is enabled), then the sustainable throughput with BFQ
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decreases, because all blkio.bfq* statistics are created and updated
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(Section 4-2). For BFQ, this leads to the following maximum
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@@ -537,19 +537,19 @@ or io.bfq.weight.
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As for cgroups-v1 (blkio controller), the exact set of stat files
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created, and kept up-to-date by bfq, depends on whether
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CONFIG_DEBUG_BLK_CGROUP is set. If it is set, then bfq creates all
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CONFIG_BFQ_CGROUP_DEBUG is set. If it is set, then bfq creates all
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the stat files documented in
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Documentation/cgroup-v1/blkio-controller.txt. If, instead,
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CONFIG_DEBUG_BLK_CGROUP is not set, then bfq creates only the files
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CONFIG_BFQ_CGROUP_DEBUG is not set, then bfq creates only the files
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blkio.bfq.io_service_bytes
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blkio.bfq.io_service_bytes_recursive
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blkio.bfq.io_serviced
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blkio.bfq.io_serviced_recursive
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The value of CONFIG_DEBUG_BLK_CGROUP greatly influences the maximum
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The value of CONFIG_BFQ_CGROUP_DEBUG greatly influences the maximum
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throughput sustainable with bfq, because updating the blkio.bfq.*
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stats is rather costly, especially for some of the stats enabled by
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CONFIG_DEBUG_BLK_CGROUP.
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CONFIG_BFQ_CGROUP_DEBUG.
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Parameters to set
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-----------------
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