On Mon 02-08-21 16:11:30, Feng Tang wrote:
> On Fri, Jul 30, 2021 at 03:18:40PM +0800, Tang, Feng wrote:
> [snip]
> > > > One thing is, it's possible that 'nd' is not set in the preferred
> > > > nodemask.
> > >
> > > Yes, and there shouldn't be any problem with that. The given node is
> > > only used to get the respective zonelist (order distance ordered list of
> > > zones to try). get_page_from_freelist will then use the preferred node
> > > mask to filter this zone list. Is that more clear now?
> >
> > Yes, from the code, the policy_node() is always coupled with
> > policy_nodemask(), which secures the 'nodemask' limit. Thanks for
> > the clarification!
>
> Hi Michal,
>
> To ensure the nodemask limit, the policy_nodemask() also needs some
> change to return the nodemask for 'prefer-many' policy, so here is a
> updated 1/6 patch, which mainly changes the node/nodemask selection
> for 'prefer-many' policy, could you review it? thanks!
right, I have mixed it with get_policy_nodemask
> @@ -1875,8 +1897,13 @@ static int apply_policy_zone(struct mempolicy *policy, enum zone_type zone)
> */
> nodemask_t *policy_nodemask(gfp_t gfp, struct mempolicy *policy)
> {
> - /* Lower zones don't get a nodemask applied for MPOL_BIND */
> - if (unlikely(policy->mode == MPOL_BIND) &&
> + int mode = policy->mode;
> +
> + /*
> + * Lower zones don't get a nodemask applied for 'bind' and
> + * 'prefer-many' policies
> + */
> + if (unlikely(mode == MPOL_BIND || mode == MPOL_PREFERRED_MANY) &&
> apply_policy_zone(policy, gfp_zone(gfp)) &&
> cpuset_nodemask_valid_mems_allowed(&policy->nodes))
> return &policy->nodes;
Isn't this just too cryptic? Why didn't you simply
if (mode == MPOL_PREFERRED_MANY)
return &policy->mode;
in addition to the existing code? I mean why would you even care about
cpusets? Those are handled at the page allocator layer and will further
filter the given nodemask.
--
Michal Hocko
SUSE Labs
