On 2017-08-07 1:19 AM, Nicholas Nethercote wrote:
I think the 2GB "requirement" from Microsoft should be ignored, because
plenty of our users are ignoring it.

By "ignore the 2GB requirement", are you suggesting we do or don't give 64-bit Firefox to users with less than 2GB?

I am waffling again on having a minimum memory requirement at all. Our current minimum is actually 1800 MB, not 2048 MB. Only about 1% of Win64 OS users actually have (0,1800) MB and only 5% have [1800,2048] MB. So we are talking about small differences in user retention and crash rates for only 1% of Win64 OS users.

As we are preparing to migrate Beta users to 64-bit, we see the minimum memory requirement adds new complexity to both the client and server components of the update process and extra QA for this one-time migration event.

On Mon, Aug 7, 2017 at 5:51 PM, Chris Peterson <cpeter...@mozilla.com>

On 2017-08-06 11:26 PM, Henri Sivonen wrote:

On Thu, Jul 20, 2017 at 10:42 AM, Chris Peterson<cpeter...@mozilla.com>

Users with only 2 GB and 5 minute browser sessions would probably have a
faster user experience with 32-bit Firefox than with 64-bit, but how do
weigh that experience versus the security benefits of ASLR?

Not giving users a security mechanism due to a non-obvious reason
feels bad. Furthermore, considering that Microsoft documents 2 GB as a
"requirement" for 64-bit Windows, is it really worthwhile for us to
treat three Windows pointer size combinations (32-bit on 32-bit,
64-bit on 64-bit and 32-bit on 64-bit) as fully supported when one of
the combinations is in contradiction with the OS vendor's stated

Do we have any metrics on whether 32-bit on 64-bit exhibits bugs that
32-bit on 32-bit and 64-bit on 64-bit don't? That is, what kind of bug
burden are we keeping by catering to users who've installed 64-bit
Windows with less than 2 GB of RAM in contradiction with what
Microsoft states as a requirement?

That's a fair question. 32-bit applications can only access 2 GB of
virtual address space on Win32 OS, but can access 4 GB on Win64 OS. So in
theory, some 32-bit pointer bugs could manifest differently on Win64 and

Do we test 32-bit Firefox on Win32 or Win64 today? I know we build 32-bit
Firefox on Win64. Since more people will run 32-bit Firefox on Win32 than
on Win64, we should probably test on Win32 or at least test on Win64
configured to only allow Firefox access to 2 GB of virtual address space.

In our experiments with Win64 OS users, users with 2 GB or less had
slightly worse retention and crash rates when running 64-bit Firefox than
32-bit Firefox.

About 8% of Win64 users in our experiment had 2 GB or less, so we are
talking about choosing a worse user experience for a fair number of people.
(We didn't break out how many users had strictly less than 2 GB.) 64-bit
Chrome's minimum memory requirement is 4 GB, so Google has similarly
decided that supporting 32-bit on Win64 is worth the trouble.

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