On 09/08/2016 02:57 AM, Fenghua Yu wrote:
> +void rdtgroup_fork(struct task_struct *child)
> +{
> + struct rdtgroup *rdtgrp;
> +
> + INIT_LIST_HEAD(&child->rg_list);
> + if (!rdtgroup_mounted)
> + return;
> +
> + mutex_lock(&rdtgroup_mutex);
> +
> + rdtgrp = current->rdtgroup;
> + if (!rdtgrp)
> + goto out;
> +
> + list_add_tail(&child->rg_list, &rdtgrp->pset.tasks);
> + child->rdtgroup = rdtgrp;
> + atomic_inc(&rdtgrp->refcount);
> +
> +out:
> + mutex_unlock(&rdtgroup_mutex);
> +}
...
> diff --git a/kernel/fork.c b/kernel/fork.c
> index beb3172..79bfc99 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -76,6 +76,7 @@
> #include <linux/compiler.h>
> #include <linux/sysctl.h>
> #include <linux/kcov.h>
> +#include <linux/resctrl.h>
>
> #include <asm/pgtable.h>
> #include <asm/pgalloc.h>
> @@ -1426,6 +1427,7 @@ static struct task_struct *copy_process(unsigned long
> clone_flags,
> p->io_context = NULL;
> p->audit_context = NULL;
> cgroup_fork(p);
> + rdtgroup_fork(p);
> #ifdef CONFIG_NUMA
> p->mempolicy = mpol_dup(p->mempolicy);
> if (IS_ERR(p->mempolicy)) {
Yikes, is this a new global lock and possible atomic_inc() on a shared
variable in the fork() path? Has there been any performance or
scalability testing done on this code?
That mutex could be a disaster for fork() once the filesystem is
mounted. Even if it goes away, if you have a large number of processes
in an rdtgroup and they are forking a lot, you're bound to see the
rdtgrp->refcount get bounced around a lot.
