With 2.2.3 we are not getting any samples with SAMPLE_RATE=1

[malkia]

Hi Daan! First thanks for the guarded implementation, we plan to use it a lot!

So after some testing, I've found that using MIMALLOC_GUARDED_SAMPLE_RATE=1 does not add pages (I've verified this with SysInternals VmMap and apart from the segments "No Access" 4kb blocks, there is nothing else.

But if I turn up the MIMALLOC_GUARDED_SAMPLE_RATE=2 then I see lots of 4kb pages (in VmMap sort by Blocks in the private shows them nicely)

I was trying to grasp the code, and I see nothing wrong why it should not run like the way it is, but this is what I'm finding (compiler bug?) not sure...

Cheers!

[malkia]

With sample rate = 1 - there would be much smaller amount of blocks

Also show stats has this: " guarded: 0"

---

WIth sample rate = 2 - quite a lot, and expanding them shows nicely 4kb "No Access" around other blocks (most of them as expected also 4Kb)

And shows stats has this instead: " guarded: 5.8 Mi"

Numbers may not match up right to the picture as as taken at different times - but pretty much shows that there is something not working with sample_rate=1

[malkia]

So really by the nature of having "No access", followed by "Read/Write" it increases the "Blocks" as they can't be coalesced into the same type, hence large amount of blocks correlates with guard pages working as expected.

Here is one of the private "heap" expanded

[daanx]

Ah, great catch! That was a weird bug -- I think it is fixed now; let me know :-)

[malkia]

Thank you Daan!!!