Disabling overcommitting memory seems to cause allocs to fail too early, what could be the reason?

I tested out echo 2 > /proc/sys/vm/overcommit_memory, which I know isn't a commonly used or recommended mode, but for various reasons it could be beneficial for some of my workloads. However, when I tested this out on a desktop system with 15.6GiB RAM, with barely a quarter of memory used, most programs would already start crashing or erroring, and Brave would fail to open tabs:

$ dmesg
...
[24551.333140] __vm_enough_memory: pid: 19014, comm: brave, bytes: 268435456 not enough memory for the allocation
[24551.417579] __vm_enough_memory: pid: 19022, comm: brave, bytes: 268435456 not enough memory for the allocation
[24552.506934] __vm_enough_memory: pid: 19033, comm: brave, bytes: 268435456 not enough memory for the allocation
$ ./smem -tkw
Area                           Used      Cache   Noncache 
firmware/hardware                 0          0          0 
kernel image                      0          0          0 
kernel dynamic memory          4.0G       3.5G     519.5M 
userspace memory               3.4G       1.3G       2.1G 
free memory                    8.2G       8.2G          0 
----------------------------------------------------------
                              15.6G      13.0G       2.7G

I understand that with overcommitting memory disabled, fork() instead of vfork() which many Linux suboptimally programs use, can cause issues once the process has more memory allocated. But it seems like this isn't the case here, since 1. the affected processes seem to at most use a few hundred megabytes of memory, and 2. the allocation listed in dmesg as failing is way smaller than what's listed as free, and 3. the overall system memory doesn't seem to be even a quarter filled up. Some more system info:

# /sbin/sysctl vm.overcommit_ratio vm.overcommit_kbytes vm.admin_reserve_kbytes vm.user_reserve_kbytes
vm.overcommit_ratio = 50
vm.overcommit_kbytes = 0
vm.admin_reserve_kbytes = 8192
vm.user_reserve_kbytes = 131072

I'm therefore wondering what the cause here is. Is there some obvious reason for this, perhaps some misconfiguration on my part that could be improved? **Update:** so, in part it seems to have been the overcommit_ratio that @StephenKitt helped me find, which needed adjustment like this:

echo 2 > /proc/sys/vm/overcommit_memory
echo 100 > /proc/sys/vm/overcommit_ratio

But now I seem to be running into another wall, and I first thought it would be the fork() vs vfork() issue, but instead it seems to be once app memory usage reaches the dynamic kernel memory: I'm guessing it may not be intended the kernel keeps sitting on this dynamic memory of more than 6GiB forever without that being usable. Does anybody have an idea why it behaves like that with overcommitting disabled? Perhaps I'm missing something here. **Update 2:** Here's more information collected when hitting this weird condition again, where the dynamic kernel memory won't get out of the way:

[32915.298484] __vm_enough_memory: pid: 24347, comm: brave, bytes: 268435456 not enough memory for the allocation
[32916.293690] __vm_enough_memory: pid: 24355, comm: brave, bytes: 268435456 not enough memory for the allocation
# exit
~/Develop/smem $ ./smem -tkw
Area                           Used      Cache   Noncache 
firmware/hardware                 0          0          0 
kernel image                      0          0          0 
kernel dynamic memory          7.8G       7.4G     384.0M 
userspace memory               5.2G       1.5G       3.7G 
free memory                    2.7G       2.7G          0 
----------------------------------------------------------
                              15.6G      11.5G       4.1G 
~/Develop/smem $ cat /proc/sys/vm/overcommit_ratio
100
~/Develop/smem $ cat /proc/sys/vm/overcommit_memory
2
~/Develop/smem $ cat /proc/meminfo 
MemTotal:       16384932 kB
MemFree:         2803496 kB
MemAvailable:   10297132 kB
Buffers:            1796 kB
Cached:          8749580 kB
SwapCached:            0 kB
Active:          7032032 kB
Inactive:        4760088 kB
Active(anon):    4698776 kB
Inactive(anon):        0 kB
Active(file):    2333256 kB
Inactive(file):  4760088 kB
Unevictable:      825908 kB
Mlocked:            1192 kB
SwapTotal:       2097148 kB
SwapFree:        2097148 kB
Zswap:                 0 kB
Zswapped:              0 kB
Dirty:               252 kB
Writeback:             0 kB
AnonPages:       3866720 kB
Mapped:          1520696 kB
Shmem:           1658104 kB
KReclaimable:     570808 kB
Slab:             743788 kB
SReclaimable:     570808 kB
SUnreclaim:       172980 kB
KernelStack:       18720 kB
PageTables:        53772 kB
SecPageTables:         0 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:    18482080 kB
Committed_AS:   17610184 kB
VmallocTotal:   261087232 kB
VmallocUsed:       86372 kB
VmallocChunk:          0 kB
Percpu:              864 kB
CmaTotal:          65536 kB
CmaFree:             608 kB