Out of curiosity, are you using the FILE_FLAG_NO_BUFFERING flag when working with large files? This provides a significant performance boost when working with large files in a sequential manner, such as a search. Currently in my use of EmEditor Pro, I’m working with files that are 1GB or more, and I seem to notice quite a bit of disk thrashing.
I’ve written some software in the past that worked with files in the 4GB to 8GB range and the overall performance of the system improved dramatically by using the FILE_FLAG_NO_BUFFERING flag for CreateFile. The only downside is you now have to read/write in 512 byte chunks, but the performance gain is well worth it.
I checked the code, and FILE_FLAG_NO_BUFFERING was not used. I have experimended a lot of flag combinations, but I will certainly try that again. You might want to check the Advanced tab of the Customize dialog box (Tools menu > Customize), and set or clear “Use Temporary File to Reduce Memory Usage” or change the numeric value here. I guess the hard disk thrashing you hear might come from either (1) Windows virtual memory swapping or (2) EmEditor temporary file usage. Thanks for your inputs!