Re: [PATCH] proc/meminfo: add MemKernel counter

[Konstantin Khlebnikov]

On 22.05.2019 18:52, Michal Hocko wrote:
> On Wed 22-05-19 17:40:09, Konstantin Khlebnikov wrote:
> > Some kinds of kernel allocations are not accounted or not show in meminfo.
> > For example vmalloc allocations are tracked but overall size is not shown
> > for performance reasons. There is no information about network buffers.
> >
> > In most cases detailed statistics is not required. At first place we need
> > information about overall kernel memory usage regardless of its structure.
> >
> > This patch estimates kernel memory usage by subtracting known sizes of
> > free, anonymous, hugetlb and caches from total memory size: MemKernel =
> > MemTotal - MemFree - Buffers - Cached - SwapCached - AnonPages - Hugetlb.
>
> Why do we need to export something that can be calculated in the
> userspace trivially? Also is this really something the number really
> meaningful? Say you have a driver that exports memory to the userspace
> via mmap but that memory is not accounted. Is this really a kernel
> memory?

It may be trivial right now but not fixed.
Adding new kinds of memory may change this definition.
For example hypothetical 'GPU buffers' may be handled as 'userspace' memory.