Lazy-Writer Thread
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8/28/2008
Each cache has its own lazy-writer thread that searches for and commits dirty sectors. By default, the priority of this thread is set to idle. However, you can override this priority for a profile, using the following registry setting:
[HKEY_LOCAL_MACHINE\System\StorageManager\Profiles\<Profile Name>\FATFS]
"LazyWriterThreadPrio256"=dword:xx
The lazy-writer thread uses the following algorithm:
if (event set indicating that there are dirty sectors to commit) {
while (TRUE){
Enter main critical section protecting the cache from main threads;
if (no more dirty sectors)
{
Leave main critical section;
break;
}
Find first dirty run of sectors to commit;
Commit those dirty sectors;
Leave main critical section;
}
}
Reset event indicating there are no dirty sectors to commit.
A main thread cannot interrupt the lazy-writer thread while it is committing dirty sectors. However, since the lazy-writer thread always leaves the main critical section, a main thread has priority in fulfilling its requests. The dirty sector check occurs while the lazy-writer thread holds the critical section to prevent race conditions. It then checks the dirty sector count and resets the event.