1fi_hook(7) Libfabric v1.8.0 fi_hook(7)
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6 fi_hook - The Hook Fabric Provider Utility
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9 The hooking provider is a utility function that can intercept calls to
10 any provider. The hook provider is always available, but has zero im‐
11 pact on calls unless enabled. It is useful for providing performance
12 data on selected calls or debugging information.
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15 Hooking support is enabled through the FI_HOOK environment variable.
16 To enable hooking, FI_HOOK must be set to the name of one or more of
17 the available hooking providers. When multiple hooks are specified,
18 the names must be separated by a semi-colon. To obtain a list of hook‐
19 ing providers available on the current system, one can use the fi_info
20 utility with the '--env' command line option. Hooking providers are
21 usually identified by 'hook' appearing in the provider name.
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23 Known hooking providers include the following:
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25 ofi_perf_hook
26 This hooks 'fast path' data operation calls. Performance data
27 is captured on call entrance and exit, in order to provide an
28 average of how long each call takes to complete. See the PER‐
29 FORMANCE HOOKS section for available performance data.
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32 The hook provider allows capturing inline performance data by accessing
33 the CPU Performance Management Unit (PMU). PMU data is only available
34 on Linux systems. Additionally, access to PMU data may be restricted
35 to privileged (super-user) applications.
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37 Performance data is captured for critical data transfer calls: fi_msg,
38 fi_rma, fi_tagged, fi_cq, and fi_cntr. Captured data is displayed as
39 logged data using the FI_LOG_LEVEL trace level. Performance data is
40 logged when the associated fabric is destroyed.
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42 The environment variable FI_PERF_CNTR is used to identify which perfor‐
43 mance counter is tracked. The following counters are available:
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45 cpu_cycles
46 Counts the number of CPU cycles each function takes to complete.
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48 cpu_instr
49 Counts the number of CPU instructions each function takes to
50 complete. This is the default performance counter if none is
51 specified.
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54 Hooking functionality is not available for providers built using the
55 FI_FABRIC_DIRECT feature. That is, directly linking to a provider pre‐
56 vents hooking.
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58 The hooking provider does not work with triggered operations. Applica‐
59 tion that use FI_TRIGGER operations that attempt to hook calls will
60 likely crash.
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63 fabric(7), fi_provider(7)
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66 OpenFabrics.
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70Libfabric Programmer's Manual 2018-10-16 fi_hook(7)