windows defender issues? & other AV issues?

Brian Milby brian at
Tue Jan 8 03:48:07 CET 2019

I think I know the issue then... look at how often the pref file is written.  Throttle/turn that off and see what happens.

I was thinking that earlier today but those test results make me want to investigate that further.

On Jan 7, 2019, 8:40 PM -0600, Richard Gaskin via use-livecode <use-livecode at>, wrote:
> J. Landman Gay wrote:
> > I'm willing to bet that any slowdown in the SE not related to AV
> > intervention is probably the new auto-complete features. I've
> > turned most of them off and I see no speed decrease.
> Same here. But since the LC IDE is written in LCS, anything it does to
> trigger this widely-documented issue with Win Defender will sooner or
> later show itself in at least some of our apps.
> They key question is: which language features are most affected?
> A Test
> -------
> Given the nature of AV, it seemed file I/O would be a likely candidate,
> but to pin that down for sure I dug up a test script that touches a wide
> range of LCS features, running it with both Defender's Real-Time
> Protection (RTP) on, and then off.
> The script was the last of a series of general performance assessment
> scripts started by Malte back in 2014, during the early v8 series. Many
> of the elements identified through the various contributions in that
> forum thread helped point the way to dramatic increases in
> frequently-used operations like lineoffset, file I/O, and others. There
> are many good test suites out there, including some from Mark Talluto,
> Curry, and others. Many may have similar breadth; I chose this one
> because I'm familiar with the specifics of its scope:
> I modified the script only slightly so that it runs in the GUI LC rather
> than LiveCode Server, and with both RTP on and off.
> Findings
> --------
> Here are the results:
> System Version: Win32 NT 10.0
> --
> Test_BuildList: 187 ms
> Test_LineOffset: 3741 ms
> Test_LineAccessByNumber: 642 ms
> Test_LineAccessForEach: 36 ms
> Test_ArraySplit: 95 ms
> Test_EncodeArray: 90 ms
> Test_DecodeArray: 114 ms
> Test_ArrayAccess: 60 ms
> Test_Merge: 1409 ms
> Test_BuildFilePath: 505 ms
> Test_FileTextWrite: 6869 ms
> Test_FileTextRead: 192 ms
> Test_FileBinWrite: 9017 ms
> Test_FileBinRead: 74 ms
> System Version: Win32 NT 10.0
> --
> Test_BuildList: 192 ms
> Test_LineOffset: 4012 ms
> Test_LineAccessByNumber: 719 ms
> Test_LineAccessForEach: 39 ms
> Test_ArraySplit: 99 ms
> Test_EncodeArray: 113 ms
> Test_DecodeArray: 143 ms
> Test_ArrayAccess: 76 ms
> Test_Merge: 1609 ms
> Test_BuildFilePath: 579 ms
> Test_FileTextWrite: 515 ms
> Test_FileTextRead: 186 ms
> Test_FileBinWrite: 376 ms
> Test_FileBinRead: 74 ms
> Most tests are close enough that any differences can be accounted for
> with expectable fluctuations in general system performance due to the
> effects of background tasks.
> But writing files - damn! Now I understand what the reporters in the
> forums have been talking about.
> The magnitude of the speed hit makes me wonder exactly what RTP is doing
> - detailed analysis of the file I/O buffer?
> Whatever it is, it's worth thinking about in terms of how it will affect
> our own apps.
> Implications for Our Own Apps
> -----------------------------
> The LC executable is signed, so while that may mitigate other AV issues,
> apparently that has no effect with the impact of file I/O ops on RTP.
> The auto-complete feature you mentioned here seems very relevant for all
> of us, because IIRC they use SQLite for that, where the driver's need to
> jump around the b-tree structure can trigger a fair bit of disk I/O.
> Even with those off, I would imagine that if you have the Dictionary tab
> open in the SE you'd see a similar impact, since Dict lookups are made
> as the selection changes.
> If there's any good news here, it's that there doesn't appear to be
> anything the team can do in the engine to avoid triggering RTP's impact.
> But the bad news may impact many of us: With apparently all disk writes
> affected, any use of a persistent local store will take a hit.
> This includes not only flat files, but databases like SQLite.
> Reading appears to have minimal impact, but while that won't affect flat
> files, some DBs may modify bits of some DB files when performing even
> read operations, so we can't completely rule out impact on what we think
> of as read-only DB operations.
> Dealing With RTP
> ----------------
> As a paranoid security freak, I can't in good conscience recommend to
> end-users to turn of any feature of their security kit.
> But on balance, it's worth noting that other AV packages do not seem to
> impact storage performance this horribly, if at all. And many of the
> more popular alternatives are generally considered better than Windows
> Defender.
> So while it seems a bit heavy-handed to tell customers which AV package
> to use, Microsoft's unusually aggressive approach to monitoring writes
> is impactful, and from the many stories with other apps we can find
> around the web, sometimes seriously.
> Maybe this is one more reason to move everything to the cloud, to end
> the tyrrany of overzealously monitored local disk I/O. :)
> I honestly don't have the quick-fix answer that will keep our customers
> happy with disk-intensive apps.
> Sugggestions?
> --
> Richard Gaskin
> Fourth World Systems
> Software Design and Development for the Desktop, Mobile, and the Web
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