On 7/22/25 2:27 PM, Kuniyuki Iwashima wrote:

On Tue, Jul 22, 2025 at 10:50 AM Shakeel Butt [off-list ref] wrote:

quoted

On Tue, Jul 22, 2025 at 10:57:31AM +0200, Michal Koutný wrote:

quoted

Hello Daniel.

On Tue, Jul 22, 2025 at 09:11:46AM +0200, Daniel Sedlak [off-list ref] wrote:

quoted

   /sys/fs/cgroup/**/<cgroup name>/memory.net.socket_pressure

The output value is an integer matching the internal semantics of the
struct mem_cgroup for socket_pressure. It is a periodic re-arm clock,
representing the end of the said socket memory pressure, and once the
clock is re-armed it is set to jiffies + HZ.

I don't find it ideal to expose this value in its raw form that is
rather an implementation detail.

IIUC, the information is possibly valid only during one jiffy interval.
How would be the userspace consuming this?

I'd consider exposing this as a cummulative counter in memory.stat for
simplicity (or possibly cummulative time spent in the pressure
condition).

Shakeel, how useful is this vmpressure per-cgroup tracking nowadays? I
thought it's kind of legacy.

Yes vmpressure is legacy and we should not expose raw underlying number
to the userspace. How about just 0 or 1 and use
mem_cgroup_under_socket_pressure() underlying? In future if we change
the underlying implementation, the output of this interface should be
consistent.

But this is available only for 1 second, and it will not be useful
except for live debugging ?

If the new interface is used mainly for debugging purpose, I will 
suggest adding the CFTYPE_DEBUG flag so that it will only show up when 
"cgroup_debug" is specified in the kernel command line.

Cheers,
Longman