Messages in this thread | | | From | Divyesh Shah <> | Date | Mon, 5 Apr 2010 09:53:25 -0700 | Subject | Re: [PATCH 3/3] blkio: Increment the blkio cgroup stats for real now |
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On Mon, Apr 5, 2010 at 8:12 AM, Vivek Goyal <vgoyal@redhat.com> wrote: > On Fri, Apr 02, 2010 at 04:36:34PM -0700, Divyesh Shah wrote: >> On Fri, Apr 2, 2010 at 12:10 PM, Vivek Goyal <vgoyal@redhat.com> wrote: >> > On Thu, Apr 01, 2010 at 03:01:41PM -0700, Divyesh Shah wrote: >> >> We also add start_time_ns and io_start_time_ns fields to struct request >> >> here to record the time when a request is created and when it is >> >> dispatched to device. We use ns uints here as ms and jiffies are >> >> not very useful for non-rotational media. >> >> >> >> Signed-off-by: Divyesh Shah<dpshah@google.com> >> >> --- >> >> >> >> block/blk-cgroup.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++-- >> >> block/blk-cgroup.h | 14 +++++++++-- >> >> block/blk-core.c | 6 +++-- >> >> block/cfq-iosched.c | 4 ++- >> >> include/linux/blkdev.h | 20 +++++++++++++++- >> >> 5 files changed, 95 insertions(+), 9 deletions(-) >> >> >> >> diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c >> >> index ad6843f..9af7257 100644 >> >> --- a/block/blk-cgroup.c >> >> +++ b/block/blk-cgroup.c >> >> @@ -15,6 +15,7 @@ >> >> #include <linux/kdev_t.h> >> >> #include <linux/module.h> >> >> #include <linux/err.h> >> >> +#include <linux/blkdev.h> >> >> #include "blk-cgroup.h" >> >> >> >> static DEFINE_SPINLOCK(blkio_list_lock); >> >> @@ -55,6 +56,26 @@ struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup) >> >> } >> >> EXPORT_SYMBOL_GPL(cgroup_to_blkio_cgroup); >> >> >> >> +/* >> >> + * Add to the appropriate stat variable depending on the request type. >> >> + * This should be called with the blkg->stats_lock held. >> >> + */ >> >> +void io_add_stat(uint64_t *stat, uint64_t add, unsigned int flags) >> >> +{ >> >> + if (flags & REQ_RW) >> >> + stat[IO_WRITE] += add; >> >> + else >> >> + stat[IO_READ] += add; >> >> + /* >> >> + * Everywhere in the block layer, an IO is treated as sync if it is a >> >> + * read or a SYNC write. We follow the same norm. >> >> + */ >> >> + if (!(flags & REQ_RW) || flags & REQ_RW_SYNC) >> >> + stat[IO_SYNC] += add; >> >> + else >> >> + stat[IO_ASYNC] += add; >> >> +} >> >> + >> > >> > Hi Divyesh, >> > >> > Can we have any request based information limited to cfq and not put that >> > in blkio-cgroup. The reason being that I am expecting that some kind of >> > max bw policy interface will not necessarily be implemented at CFQ >> > level. We might have to implement it at higher level so that it can >> > work with all dm/md devices. If that's the case, then it might very well >> > be either a bio based interface also. >> > >> > So just keeping that possibility in mind, can we keep blk-cgroup as >> > generic as possible and not necessarily make it dependent on "struct >> > request". >> >> Ok. I do understand the motivation for keeping the request related >> info out of blk-cgroup. Everything except the rq->cmd_flags can be >> easily done away with. Maybe I'll need to have CFQ send the sync and >> direction bits as args to the functions that need it. Not ideal coz >> we'll have functions with many args but I guess its not that bad too. >> >> > >> > If you implement, two dimensional arrays for stats then we can have >> > following function. >> > >> > blkio_add_stat(enum stat_type var enum stat_sub_type var_type, u64 val) >> >> I would want to avoid calls like these from CFQ into the blkcg code >> because many CFQ events trigger update for multiple stats (you'll see >> more with stats in later patchsets) and doing these calls >> independently for each stat would mean that we would also need to grab >> the stats_lock multiple times when we could've avoided that. > > I understand the need to club the updates and reduce the need of taking > stats_lock multiple times. I was thinking of any of following. > > - Get rid of reset interface per cgroup. Rely on changing ioscheduler on > request queue and that will get rid of stats_lock entirely.
This takes away the ability to reset stats at will which is very useful when debugging and for testing IO controller.
> - Can we use a function blkio_add_stat() with variable number of arguments > so that more than one stat can be updated in a single call?
I really don't like this at all.
> If you have other ideas to implement it without assuming "struct rq" in > blk-cgroup, please do that.
I've already got rid of any rq assumptions in blk-cgroup. The only place where we're using rq is for rq_start_time_ns() and rq_io-start_time_ns() functions but they are not used by the blk-cgroup code directly (only CFQ uses them). For another user of io-controller, we can implement a bio based functions.
> > Thanks > Vivek > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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