public void ColdStart_JitFailuresTest()
{
var path = Path.Combine(Path.GetDirectoryName(new Uri(typeof(HostWarmupMiddleware).Assembly.CodeBase).LocalPath), WarmUpConstants.PreJitFolderName, WarmUpConstants.JitTraceFileName);
var file = new FileInfo(path);
Assert.True(file.Exists, $"Expected PGO file '{file.FullName}' does not exist. The file was either renamed or deleted.");
JitTraceRuntime.Prepare(file, out int successfulPrepares, out int failedPrepares);
var failurePercentage = (double)failedPrepares / successfulPrepares * 100;
// using 1% as approximate number of allowed failures before we need to regenrate a new PGO file.
Assert.True(failurePercentage < 1.0, $"Number of failed PGOs are more than 1 percent! Current number of failures are {failedPrepares}. This will definitely impact cold start! Time to regenrate PGOs and update the {WarmUpConstants.JitTraceFileName} file!");
}
private void PreJitPrepare()
{
// This is to PreJIT all methods captured in coldstart.jittrace file to improve cold start time
var path = Path.Combine(Path.GetDirectoryName(new Uri(typeof(HostWarmupMiddleware).Assembly.CodeBase).LocalPath), WarmUpConstants.PreJitFolderName, WarmUpConstants.JitTraceFileName);
var file = new FileInfo(path);
if (file.Exists)
{
JitTraceRuntime.Prepare(file, out int successfulPrepares, out int failedPrepares);
// We will need to monitor failed vs success prepares and if the failures increase, it means code paths have diverged or there have been updates on dotnet core side.
// When this happens, we will need to regenerate the coldstart.jittrace file.
_logger.LogInformation(new EventId(100, "PreJit"), $"PreJIT Successful prepares: {successfulPrepares}, Failed prepares: {failedPrepares}");
}
}