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| -rw-r--r-- | Documentation/block/bfq-iosched.txt | 17 |
1 files changed, 11 insertions, 6 deletions
diff --git a/Documentation/block/bfq-iosched.txt b/Documentation/block/bfq-iosched.txt index 3d6951d63489..7a9361508157 100644 --- a/Documentation/block/bfq-iosched.txt +++ b/Documentation/block/bfq-iosched.txt @@ -20,12 +20,17 @@ for that device, by setting low_latency to 0. See Section 3 for details on how to configure BFQ for the desired tradeoff between latency and throughput, or on how to maximize throughput. -On average CPUs, the current version of BFQ can handle devices -performing at most ~30K IOPS; at most ~50 KIOPS on faster CPUs. As a -reference, 30-50 KIOPS correspond to very high bandwidths with -sequential I/O (e.g., 8-12 GB/s if I/O requests are 256 KB large), and -to 120-200 MB/s with 4KB random I/O. BFQ is currently being tested on -multi-queue devices too. +BFQ has a non-null overhead, which limits the maximum IOPS that the +CPU can process for a device scheduled with BFQ. To give an idea of +the limits on slow or average CPUs, here are BFQ limits for three +different CPUs, on, respectively, an average laptop, an old desktop, +and a cheap embedded system, in case full hierarchical support is +enabled (i.e., CONFIG_BFQ_GROUP_IOSCHED is set): +- Intel i7-4850HQ: 250 KIOPS +- AMD A8-3850: 170 KIOPS +- ARM CortexTM-A53 Octa-core: 45 KIOPS + +BFQ works for multi-queue devices too. The table of contents follow. Impatients can just jump to Section 3. |