On Wed, 22 Nov 2023 16:11:49 -0500 Gregory Price <gourry.memverge@xxxxxxxxx> wrote: > The patch set changes task->mempolicy to be modifiable by tasks other > than just current. > > The ultimate goal is to make mempolicy more flexible and extensible, > such as adding interleave weights (which may need to change at runtime > due to hotplug events). Making mempolicy externally modifiable allows > for userland daemons to make runtime performance adjustments to running > tasks without that software needing to be made numa-aware. Please add to this [0/N] a full description of the security aspect: who can modify whose mempolicy, along with a full description of the reasoning behind this decision. > 3. Add external interfaces which allow for a task mempolicy to be > modified by another task. This is implemented in 4 syscalls > and a procfs interface: > sys_set_task_mempolicy > sys_get_task_mempolicy > sys_set_task_mempolicy_home_node > sys_task_mbind > /proc/[pid]/mempolicy Why is the procfs interface needed? Doesn't it simply duplicate the syscall interface? Please update [0/N] with a description of this decision. > The new syscalls are the same as their current-task counterparts, > except that they take a pid as an argument. The exception is > task_mbind, which required a new struct due to the number of args. > > The /proc/pid/mempolicy re-uses the interface mpol_parse_str format > to enable get/set of mempolicy via procsfs. > > mpol_parse_str format: > <mode>[=<flags>][:<nodelist>] > > Example usage: > > echo "default" > /proc/pid/mempolicy > echo "prefer=relative:0" > /proc/pid/mempolicy > echo "interleave:0-3" > /proc/pid/mempolicy What do we get when we read from this? Please add to changelog. > Changing the mempolicy does not induce memory migrations via the > procfs interface (which is the exact same behavior as set_mempolicy). >
