On Wed, Jun 30, 2021 at 11:51 AM Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote: > > On Wed, Jun 30, 2021 at 11:26 AM Andy Lutomirski <luto@xxxxxxxxxx> wrote: > > > > On Wed, Jun 23, 2021 at 12:28 PM Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote: > > > > > > In modern systems it's not unusual to have a system component monitoring > > > memory conditions of the system and tasked with keeping system memory > > > pressure under control. One way to accomplish that is to kill > > > non-essential processes to free up memory for more important ones. > > > Examples of this are Facebook's OOM killer daemon called oomd and > > > Android's low memory killer daemon called lmkd. > > > For such system component it's important to be able to free memory > > > quickly and efficiently. Unfortunately the time process takes to free > > > up its memory after receiving a SIGKILL might vary based on the state > > > of the process (uninterruptible sleep), size and OPP level of the core > > > the process is running. A mechanism to free resources of the target > > > process in a more predictable way would improve system's ability to > > > control its memory pressure. > > > Introduce process_reap system call that reclaims memory of a dying process > > > from the context of the caller. This way the memory in freed in a more > > > controllable way with CPU affinity and priority of the caller. The workload > > > of freeing the memory will also be charged to the caller. > > > The operation is allowed only on a dying process. > > > > At the risk of asking a potentially silly question, should this just > > be a file in procfs? > > Hmm. I guess it's doable if procfs will not disappear too soon before > memory is released... syscall also supports parameters, in this case > flags can be used in the future to support PIDs in addition to PIDFDs > for example. > Before looking more in that direction, a silly question from my side: > why procfs interface would be preferable to a syscall? It avoids using a syscall nr. (Admittedly a syscall nr is not *that* precious of a resource.) It also makes it possible to use a shell script to do this, which is maybe useful. --Andy
