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Diffstat (limited to 'share/man/man4/ioat.4')
| -rw-r--r-- | share/man/man4/ioat.4 | 20 |
1 files changed, 19 insertions, 1 deletions
diff --git a/share/man/man4/ioat.4 b/share/man/man4/ioat.4 index faa22ae..7ba7768 100644 --- a/share/man/man4/ioat.4 +++ b/share/man/man4/ioat.4 @@ -24,7 +24,7 @@ .\" .\" $FreeBSD$ .\" -.Dd December 9, 2015 +.Dd December 14, 2015 .Dt IOAT 4 .Os .Sh NAME @@ -63,6 +63,10 @@ In .Fn ioat_get_dmaengine "uint32_t channel_index" .Ft void .Fn ioat_put_dmaengine "bus_dmaengine_t dmaengine" +.Ft int +.Fn ioat_set_interrupt_coalesce "bus_dmaengine_t dmaengine" "uint16_t delay" +.Ft uint16_t +.Fn ioat_get_max_coalesce_period "bus_dmaengine_t dmaengine" .Ft void .Fn ioat_acquire "bus_dmaengine_t dmaengine" .Ft void @@ -129,6 +133,20 @@ flag. For example, a user might submit multiple operations to the same channel and only enable an interrupt and callback for the last operation. .Pp +The hardware can delay and coalesce interrupts on a given channel for a +configurable period of time, in microseconds. +This may be desired to reduce the processing and interrupt overhead per +descriptor, especially for workflows consisting of many small operations. +Software can control this on a per-channel basis with the +.Fn ioat_set_interrupt_coalesce +API. +The +.Fn ioat_get_max_coalesce_period +API can be used to determine the maximum coalescing period supported by the +hardware, in microseconds. +Current platforms support up to a 16.383 millisecond coalescing period. +Optimal configuration will vary by workflow and desired operation latency. +.Pp All operations are safe to use in a non-blocking context with the .Ar DMA_NO_WAIT flag. |
