networking:napi
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networking:napi [2016/08/12 05:22] AliceSmith [Hardware Architecture] |
networking:napi [2022/10/16 16:55] (current) joser93 Missed the issues header. now fixed. |
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| =====Contents===== | =====Contents===== | ||
| - | * [[https://www.linuxfoundation.org/#NAPI_Driver_design|1 NAPI Driver design]] | + | * [[#NAPI_Driver_design|1 NAPI Driver design]] |
| - | * [[https://www.linuxfoundation.org/#Hardware_Architecture|1.1 Hardware Architecture]] | + | * [[#Hardware_Architecture|1.1 Hardware Architecture]] |
| - | * [[https://www.linuxfoundation.org/#Locking_rules_and_environmental_guarantees|1.2 Locking rules and environmental guarantees]] | + | * [[#Locking_rules_and_environmental_guarantees|1.2 Locking rules and environmental guarantees]] |
| - | * [[https://www.linuxfoundation.org/#NAPI_API|2 NAPI API]] | + | * [[#NAPI_API|2 NAPI API]] |
| - | * [[https://www.linuxfoundation.org/#Advantages|3 Advantages]] | + | * [[#Advantages|3 Advantages]] |
| - | * [[https://www.linuxfoundation.org/#Performance_under_high_packet_load|3.1 Performance under high packet load]] | + | * [[#Performance_under_high_packet_load|3.1 Performance under high packet load]] |
| - | * [[https://www.linuxfoundation.org/#Use_of_softirq_for_other_optimizations|3.2 Use of softirq for other optimizations]] | + | * [[#Use_of_softirq_for_other_optimizations|3.2 Use of softirq for other optimizations]] |
| - | * [[https://www.linuxfoundation.org/#Hardware_Flow_control|3.3 Hardware Flow control]] | + | * [[#Hardware_Flow_control|3.3 Hardware Flow control]] |
| - | * [[https://www.linuxfoundation.org/#Disadvantages|4 Disadvantages]] | + | * [[#Disadvantages|4 Disadvantages]] |
| - | * [[https://www.linuxfoundation.org/#Latency|4.1 Latency]] | + | * [[#Latency|4.1 Latency]] |
| - | * [[https://www.linuxfoundation.org/#IRQ_masking|4.2 IRQ masking]] | + | * [[#IRQ_masking|4.2 IRQ masking]] |
| - | * [[https://www.linuxfoundation.org/#Issues|5 Issues]] | + | * [[#Issues|5 Issues]] |
| - | * [[https://www.linuxfoundation.org/#IRQ_race_a.k.a_rotting_packet|5.1 IRQ race a.k.a rotting packet]] | + | * [[#IRQ_race_a.k.a_rotting_packet|5.1 IRQ race a.k.a rotting packet]] |
| - | * [[https://www.linuxfoundation.org/#IRQ_mask_and_level-triggered|5.1.1 IRQ mask and level-triggered]] | + | * [[#IRQ_mask_and_level-triggered|5.1.1 IRQ mask and level-triggered]] |
| - | * [[https://www.linuxfoundation.org/#non-level_sensitive_IRQs|5.1.2 non-level sensitive IRQs]] | + | * [[#non-level_sensitive_IRQs|5.1.2 non-level sensitive IRQs]] |
| - | * [[https://www.linuxfoundation.org/#Scheduling_issues|5.2 Scheduling issues]] | + | * [[#Scheduling_issues|5.2 Scheduling issues]] |
| - | * [[https://www.linuxfoundation.org/#External_Links|6 External Links]] | + | * [[#External_Links|6 External Links]] |
| =====NAPI Driver design===== | =====NAPI Driver design===== | ||
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| * Only one CPU at any time can call napi->poll(); for each ''napi_struct'' this is because only one CPU can pick the initial interrupt and hence the initial //napi_schedule(napi)// | * Only one CPU at any time can call napi->poll(); for each ''napi_struct'' this is because only one CPU can pick the initial interrupt and hence the initial //napi_schedule(napi)// | ||
| - | * The core layer invokes devices to send packets in a round robin format. This implies receive is totaly lockless because of the guarantee only that one CPU is executing it. | + | * The core layer invokes devices to send packets in a round robin format. This implies receive is totaly lockless because of the guarantee that only one CPU is executing it. |
| * Contention can only be the result of some other CPU accessing the rx ring. This happens only in close() and suspend() (when these methods try to clean the rx ring); Driver authors need not worry about this; synchronization is taken care for them by the top net layer. | * Contention can only be the result of some other CPU accessing the rx ring. This happens only in close() and suspend() (when these methods try to clean the rx ring); Driver authors need not worry about this; synchronization is taken care for them by the top net layer. | ||
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| * **napi_schedule_prep(napi) ** | * **napi_schedule_prep(napi) ** | ||
| * puts ''napi'' in a state ready to be added to the CPU polling list if it is up and running. You can look at this as the first half of //napi_schedule(napi)//. | * puts ''napi'' in a state ready to be added to the CPU polling list if it is up and running. You can look at this as the first half of //napi_schedule(napi)//. | ||
| - | * **__napi_schedule(napi) ** | + | * **<nowiki>__napi_schedule(napi)</nowiki>** |
| - | * Add ''napi'' to the poll list for this CPU; assuming that //napi_prep(napi)// has already been called and returned 1 | + | * Add ''napi'' to the poll list for this CPU; assuming that //napi_schedule_prep(napi)// has already been called and returned 1 |
| * **napi_reschedule(napi) ** | * **napi_reschedule(napi) ** | ||
| * Called to reschedule polling for ''napi'' specifically for some deficient hardware. | * Called to reschedule polling for ''napi'' specifically for some deficient hardware. | ||
| * **napi_complete(napi) ** | * **napi_complete(napi) ** | ||
| - | * Remove ''napi'' from the CPU poll list: it must be in the poll list on current cpu. This primitive is called by napi->poll(), when it completes its work. The structure cannot be out of poll list at this call, if it is then clearly it is a BUG(). | + | * Remove ''napi'' from the CPU poll list: it must be in the poll list on current cpu. This primitive is called by //<nowiki>napi->poll()</nowiki>//, when it completes its work. The structure cannot be out of poll list at this call, if it is then clearly it is a BUG(). |
| - | * **__napi_complete(napi) ** | + | * **<nowiki>__napi_complete(napi)</nowiki>** |
| - | * same as **napi_complete** but called when local interrupts are already disabled. | + | * same as //napi_complete// but called when local interrupts are already disabled. |
| * **napi_disable(napi)** | * **napi_disable(napi)** | ||
| * Temporarily disables ''napi'' structure from being polled. May sleep if it is currently being polled | * Temporarily disables ''napi'' structure from being polled. May sleep if it is currently being polled | ||
networking/napi.1470979367.txt.gz · Last modified: 2016/08/12 05:22 by AliceSmith
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