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Diffstat (limited to 'src/vm/perfdefaults.h')
| -rw-r--r-- | src/vm/perfdefaults.h | 90 |
1 files changed, 90 insertions, 0 deletions
diff --git a/src/vm/perfdefaults.h b/src/vm/perfdefaults.h new file mode 100644 index 0000000000..1420995a98 --- /dev/null +++ b/src/vm/perfdefaults.h @@ -0,0 +1,90 @@ +// Licensed to the .NET Foundation under one or more agreements. +// The .NET Foundation licenses this file to you under the MIT license. +// See the LICENSE file in the project root for more information. +// +// -------------------------------------------------------------------------------------------------- +// PerfDefaults.h +// + +// +// Implementation of the "PerformanceScenario" config option, which defines a workload-specific +// set of performance defaults. +// +// The motivation is that every release we work closely with a partner to understand the performance +// of their scenario and provide CLR behavior to improve it. Sometimes we are able to give them +// an entirely different build of the CLR (because it happens to be on a different architecture, or +// it needs to have a small size, etc), but not always. Sometimes we are able to change the +// runtime to have the new behavior by default, but not always. When neither applies, we fall to +// the ugly option of a set of one-off config values for the scenario (or machine administrators) +// to opt in. This then creates the problem of a huge number of generic knobs that any application +// can use in any combination. It also means that as we add additional improvements for the same +// scenario, we need to ask developers or machine administrators to keep up with the growing list. +// +// Our solution is to opt-in to a set of performance settings all at once and based on the workload. +// When a recognized 'PerformanceScenario' is specified in a config file, we want the runtime to +// operate with a defined set of performance settings. This set may evolve over time to +// automatically provide additional behavior to the same workload, just as we would for runtime +// defaults. Note however that a key design point is that in any conflict between these performance +// settings and one that is explicitly set by the user, the explicit user setting wins. Hence the +// name PerformanceDefaults -- it is as if we had created a separate build of the runtime for a +// particular scenario, changing only the default performance behavior, and continued to let people +// opt in or opt-out individually to those settings that are important and general-purpose enough +// to have an individual setting. +// +// To add a scenario, +// Update the PerformanceScenario enum and InitializeForScenario so that it is recognized +// +// To add an overridden host STARTUP_FLAG, +// Update the switch statement in GetModifiedStartupFlags; see note about IsConfigOptionSpecified +// +// To add an overridden CLRConfig default value, +// Mark it with LookupOption CLRConfig::MayHavePerformanceDefault in clrconfigvalues.h +// Update the switch statement in LookupConfigValue +// If a new CLRConfig option, decide if it needs to be a general-purpose switch (hopefully no) +// and if not create it as INTERNAL_ +// +// -------------------------------------------------------------------------------------------------- + + +#ifndef __PerfDefaults_h__ +#define __PerfDefaults_h__ + +class PerformanceDefaults +{ +public: + + static void InitializeForScenario(__in_opt LPWSTR scenarioName); + + // Called at runtime startup to allow host-specified STARTUP_FLAGS to be overridden when running + // under a scenario. + // + // Note that this does not follow the model of "only override if not specified." By the nature + // of the startup flags being bits, they are all specified (as on or off). We have no way of + // knowing which the host actually care about and which were left as the runtime default + // out of lack of concern. However we found that so far the specified startup flags are hard + // coded by the host (no way for the user to override at run time) and so we can build in + // to the set of defaults which the host allows us to override. + // + // In the future, if a host needs us to be able to override startup flags conditionally, the + // solution would be a new hosting API ICLRRuntimeInfo::SetOverridableStartupFlags. + static STARTUP_FLAGS GetModifiedStartupFlags(STARTUP_FLAGS originalFlags); + + // Called by the CLRConfig system whenever a 'MayHavePerformanceDefault' config option is about + // to resolve to its runtime default (i.e. none of the corresponding environment variable, + // registry, or config file values were specified). + static BOOL LookupConfigValue(LPCWSTR name, DWORD *pValue); + +private: + + enum PerformanceScenario + { + Uninitialized, + None, + HighDensityWebHosting, + }; + + static PerformanceScenario s_Scenario; + +}; + +#endif //__PerfDefaults_h__ |