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SubjectRe: [RFC][PATCH 02/11] blkiocg async: The main part of iotrack
On Thu, 08 Jul 2010 23:15:30 -0400
Munehiro Ikeda <m-ikeda@ds.jp.nec.com> wrote:

> Signed-off-by: Hirokazu Takahashi <taka@valinux.co.jp>
> Signed-off-by: Ryo Tsuruta <ryov@valinux.co.jp>
> Signed-off-by: Andrea Righi <arighi@develer.com>
> Signed-off-by: Munehiro "Muuhh" Ikeda <m-ikeda@ds.jp.nec.com>
> ---
> block/Kconfig.iosched | 8 +++
> block/Makefile | 1 +
> block/blk-iotrack.c | 129 +++++++++++++++++++++++++++++++++++++++++++
> include/linux/blk-iotrack.h | 62 +++++++++++++++++++++
> include/linux/page_cgroup.h | 25 ++++++++
> init/Kconfig | 2 +-
> mm/page_cgroup.c | 91 +++++++++++++++++++++++++++---
> 7 files changed, 309 insertions(+), 9 deletions(-)
> create mode 100644 block/blk-iotrack.c
> create mode 100644 include/linux/blk-iotrack.h
>
> diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
> index 3199b76..3ab712d 100644
> --- a/block/Kconfig.iosched
> +++ b/block/Kconfig.iosched
> @@ -43,6 +43,14 @@ config CFQ_GROUP_IOSCHED
> ---help---
> Enable group IO scheduling in CFQ.
>
> +config GROUP_IOSCHED_ASYNC
> + bool "CFQ Group Scheduling for async IOs (EXPERIMENTAL)"
> + depends on CFQ_GROUP_IOSCHED && EXPERIMENTAL
> + select MM_OWNER
> + default n
> + help
> + Enable group IO scheduling for async IOs.
> +
> choice
> prompt "Default I/O scheduler"
> default DEFAULT_CFQ
> diff --git a/block/Makefile b/block/Makefile
> index 0bb499a..441858d 100644
> --- a/block/Makefile
> +++ b/block/Makefile
> @@ -9,6 +9,7 @@ obj-$(CONFIG_BLOCK) := elevator.o blk-core.o blk-tag.o blk-sysfs.o \
>
> obj-$(CONFIG_BLK_DEV_BSG) += bsg.o
> obj-$(CONFIG_BLK_CGROUP) += blk-cgroup.o
> +obj-$(CONFIG_GROUP_IOSCHED_ASYNC) += blk-iotrack.o
> obj-$(CONFIG_IOSCHED_NOOP) += noop-iosched.o
> obj-$(CONFIG_IOSCHED_DEADLINE) += deadline-iosched.o
> obj-$(CONFIG_IOSCHED_CFQ) += cfq-iosched.o
> diff --git a/block/blk-iotrack.c b/block/blk-iotrack.c
> new file mode 100644
> index 0000000..d98a09a
> --- /dev/null
> +++ b/block/blk-iotrack.c
> @@ -0,0 +1,129 @@
> +/* blk-iotrack.c - Block I/O Tracking
> + *
> + * Copyright (C) VA Linux Systems Japan, 2008-2009
> + * Developed by Hirokazu Takahashi <taka@valinux.co.jp>
> + *
> + * Copyright (C) 2010 Munehiro Ikeda <m-ikeda@ds.jp.nec.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/sched.h>
> +#include <linux/mm.h>
> +#include <linux/memcontrol.h>
> +#include <linux/mm_inline.h>
> +#include <linux/rcupdate.h>
> +#include <linux/module.h>
> +#include <linux/blkdev.h>
> +#include <linux/blk-iotrack.h>
> +#include "blk-cgroup.h"
> +
> +/*
> + * The block I/O tracking mechanism is implemented on the cgroup memory
> + * controller framework. It helps to find the the owner of an I/O request
> + * because every I/O request has a target page and the owner of the page
> + * can be easily determined on the framework.
> + */
> +
> +/* Return the blkio_cgroup that associates with a process. */
> +static inline struct blkio_cgroup *task_to_blkio_cgroup(struct task_struct *p)
> +{
> + return cgroup_to_blkio_cgroup(task_cgroup(p, blkio_subsys_id));
> +}
> +
> +/**
> + * blk_iotrack_set_owner() - set the owner ID of a page.
> + * @page: the page we want to tag
> + * @mm: the mm_struct of a page owner
> + *
> + * Make a given page have the blkio-cgroup ID of the owner of this page.
> + */
> +int blk_iotrack_set_owner(struct page *page, struct mm_struct *mm)
> +{
> + struct blkio_cgroup *blkcg;
> + unsigned short id = 0; /* 0: default blkio_cgroup id */
> +
> + if (blk_iotrack_disabled())
> + return 0;
> + if (!mm)
> + goto out;
> +
> + rcu_read_lock();
> + blkcg = task_to_blkio_cgroup(rcu_dereference(mm->owner));
> + if (likely(blkcg))
> + id = css_id(&blkcg->css);
> + rcu_read_unlock();
> +out:
> + return page_cgroup_set_owner(page, id);
> +}
> +

I think this is bad. I/O should be charged against threads i.e. "current",
because CFQ/blockio-cgroup provides per-thread control.
mm->owner is not suitable, I think.

Thank,s
-Kame




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