Messages in this thread | | | Subject | Re: [bug report] resctrl high memory comsumption | From | Reinette Chatre <> | Date | Wed, 8 Jan 2020 12:42:17 -0800 |
| |
Hi Fenghua,
On 1/8/2020 12:23 PM, Fenghua Yu wrote: > On Wed, Jan 08, 2020 at 09:07:41AM -0800, Shakeel Butt wrote: >> Hi, >> >> Recently we had a bug in the system software writing the same pids to >> the tasks file of resctrl group multiple times. The resctrl code >> allocates "struct task_move_callback" for each such write and call >> task_work_add() for that task to handle it on return to user-space >> without checking if such request already exist for that particular >> task. The issue arises for long sleeping tasks which has thousands for >> such request queued to be handled. On our production, we notice >> thousands of tasks having thousands of such requests and taking GiBs >> of memory for "struct task_move_callback". I am not very familiar with >> the code to judge if task_work_cancel() is the right approach or just >> checking closid/rmid before doing task_work_add(). >> > > Thank you for reporting the issue, Shakeel! > > Could you please check if the following patch fixes the issue? > From 3c23c39b6a44fdfbbbe0083d074dcc114d7d7f1c Mon Sep 17 00:00:00 2001 > From: Fenghua Yu <fenghua.yu@intel.com> > Date: Wed, 8 Jan 2020 19:53:33 +0000 > Subject: [RFC PATCH] x86/resctrl: Fix redundant task movements > > Currently a task can be moved to a rdtgroup multiple times. > But, this can cause multiple task works are added, waste memory > and degrade performance. > > To fix the issue, only move the task to a rdtgroup when the task > is not in the rdgroup. Don't try to move the task to the rdtgroup > again when the task is already in the rdtgroup. > > Reported-by: Shakeel Butt <shakeelb@google.com> > Signed-off-by: Fenghua Yu <fenghua.yu@intel.com> > --- > arch/x86/kernel/cpu/resctrl/rdtgroup.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c > index 2e3b06d6bbc6..75300c4a5969 100644 > --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c > +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c > @@ -546,6 +546,17 @@ static int __rdtgroup_move_task(struct task_struct *tsk, > struct task_move_callback *callback; > int ret; > > + /* If the task is already in rdtgrp, don't move the task. */ > + if ((rdtgrp->type == RDTCTRL_GROUP && tsk->closid == rdtgrp->closid && > + tsk->rmid == rdtgrp->mon.rmid) || > + (rdtgrp->type == RDTMON_GROUP && > + rdtgrp->mon.parent->closid == tsk->closid && > + tsk->rmid == rdtgrp->mon.rmid)) { > + rdt_last_cmd_puts("Task is already in the rdgroup\n"); > + > + return -EINVAL; > + } > + > callback = kzalloc(sizeof(*callback), GFP_KERNEL); > if (!callback) > return -ENOMEM; >
I think your fix would address this specific use case but a slightly different use case will still encounter the problem of high memory consumption. If for example, sleeping tasks are moved (many times) between resource or monitoring groups then their task_works queue would just keep growing. It seems that a call to task_work_cancel() before adding a new work item should address all these cases?
Reinette
| |