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    SubjectRe: [PATCH 06/21] blkio: Introduce blkio controller cgroup interface
    On Tue, Dec 01, 2009 at 05:34:37AM +0530, Divyesh Shah wrote:
    > On Mon, Nov 30, 2009 at 8:29 AM, Vivek Goyal <vgoyal@redhat.com> wrote:
    > > o This is basic implementation of blkio controller cgroup interface. This is
    > >  the common interface visible to user space and should be used by different
    > >  IO control policies as we implement those.
    > >
    > > Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
    > > ---
    > >  block/Kconfig                 |   13 +++
    > >  block/Kconfig.iosched         |    1 +
    > >  block/Makefile                |    1 +
    > >  block/blk-cgroup.c            |  177 +++++++++++++++++++++++++++++++++++++++++
    > >  block/blk-cgroup.h            |   58 +++++++++++++
    > >  include/linux/cgroup_subsys.h |    6 ++
    > >  include/linux/iocontext.h     |    4 +
    > >  7 files changed, 260 insertions(+), 0 deletions(-)
    > >  create mode 100644 block/blk-cgroup.c
    > >  create mode 100644 block/blk-cgroup.h
    > >
    > > diff --git a/block/Kconfig b/block/Kconfig
    > > index 9be0b56..6ba1a8e 100644
    > > --- a/block/Kconfig
    > > +++ b/block/Kconfig
    > > @@ -77,6 +77,19 @@ config BLK_DEV_INTEGRITY
    > >        T10/SCSI Data Integrity Field or the T13/ATA External Path
    > >        Protection.  If in doubt, say N.
    > >
    > > +config BLK_CGROUP
    > > +       bool
    > > +       depends on CGROUPS
    > > +       default n
    > > +       ---help---
    > > +       Generic block IO controller cgroup interface. This is the common
    > > +       cgroup interface which should be used by various IO controlling
    > > +       policies.
    > > +
    > > +       Currently, CFQ IO scheduler uses it to recognize task groups and
    > > +       control disk bandwidth allocation (proportional time slice allocation)
    > > +       to such task groups.
    > > +
    > >  endif # BLOCK
    > >
    > >  config BLOCK_COMPAT
    > > diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
    > > index 8bd1051..be0280d 100644
    > > --- a/block/Kconfig.iosched
    > > +++ b/block/Kconfig.iosched
    > > @@ -23,6 +23,7 @@ config IOSCHED_DEADLINE
    > >
    > >  config IOSCHED_CFQ
    > >        tristate "CFQ I/O scheduler"
    > > +       select BLK_CGROUP
    > >        default y
    > >        ---help---
    > >          The CFQ I/O scheduler tries to distribute bandwidth equally
    > > diff --git a/block/Makefile b/block/Makefile
    > > index 7914108..cb2d515 100644
    > > --- a/block/Makefile
    > > +++ b/block/Makefile
    > > @@ -8,6 +8,7 @@ obj-$(CONFIG_BLOCK) := elevator.o blk-core.o blk-tag.o blk-sysfs.o \
    > >                        blk-iopoll.o ioctl.o genhd.o scsi_ioctl.o
    > >
    > >  obj-$(CONFIG_BLK_DEV_BSG)      += bsg.o
    > > +obj-$(CONFIG_BLK_CGROUP)       += blk-cgroup.o
    > >  obj-$(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-cgroup.c b/block/blk-cgroup.c
    > > new file mode 100644
    > > index 0000000..4f6afd7
    > > --- /dev/null
    > > +++ b/block/blk-cgroup.c
    > > @@ -0,0 +1,177 @@
    > > +/*
    > > + * Common Block IO controller cgroup interface
    > > + *
    > > + * Based on ideas and code from CFQ, CFS and BFQ:
    > > + * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
    > > + *
    > > + * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
    > > + *                   Paolo Valente <paolo.valente@unimore.it>
    > > + *
    > > + * Copyright (C) 2009 Vivek Goyal <vgoyal@redhat.com>
    > > + *                   Nauman Rafique <nauman@google.com>
    > > + */
    > > +#include <linux/ioprio.h>
    > > +#include "blk-cgroup.h"
    > > +
    > > +struct blkio_cgroup blkio_root_cgroup = { .weight = 2*BLKIO_WEIGHT_DEFAULT };
    >
    > This should use BLKIO_WEIGHT_MAX as 2*BLKIO_WEIGHT_DEFAULT is same as
    > BLKIO_WEIGHT_MAX unless there is a reason why you would want the value
    > to remain as a multiple of default_weight instead of max in case the
    > constants change later.
    >

    Hi Divyesh,

    Every new group gets the weight as BLKIO_WEIGHT_DEFAULT. For root group by
    default I wanted to give it double the weight to begin with as it will
    have all the async queues, will also have all the sync-noidle queues
    (in case of group_isolation=0) and will be doing all the system IO.

    That's a different thing that 2*BLKIO_WEIGHT_DEFAULT happens to be same
    as BLKIO_WEIGHT_MAX.

    So functionality wise it does not change anything. It is just a matter of
    what is more intutive as a root group default.

    To me 2*BLKIO_WEIGHT_DEFAULT looks just fine. So I will keep it as it is,
    unless you really think that it is not intutive and BLKIO_WEIGHT_MAX is
    more intutive.

    Thanks
    Vivek
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