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SubjectRe: [PATCH 3/6 v4] cfq-iosched: Introduce vdisktime and io weight for CFQ queue
Vivek Goyal wrote:
> On Thu, Feb 10, 2011 at 03:47:16PM +0800, Gui Jianfeng wrote:
>> Introduce vdisktime and io weight for CFQ queue scheduling. Currently, io priority
>> maps to a range [100,1000]. It also gets rid of cfq_slice_offset() logic and makes
>> use the same scheduling algorithm as CFQ group does. This helps for CFQ queue and
>> group scheduling on the same service tree.
>>
>> Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
>> ---
>> block/cfq-iosched.c | 219 +++++++++++++++++++++++++++++++++++++++------------
>> 1 files changed, 167 insertions(+), 52 deletions(-)
>>
>> diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
>> index f3a126e..41cef2e 100644
>> --- a/block/cfq-iosched.c
>> +++ b/block/cfq-iosched.c
>> @@ -39,6 +39,13 @@ static const int cfq_hist_divisor = 4;
>> */
>> #define CFQ_IDLE_DELAY (HZ / 5)
>>
>> +/*
>> + * The base boosting value.
>> + */
>> +#define CFQ_BOOST_SYNC_BASE (HZ / 10)
>> +#define CFQ_BOOST_ASYNC_BASE (HZ / 25)
>> +
>
> These are same as cfq_slice_sync and cfq_slice_async. Looking at
> boost logic, this is equivalent of starting a new queue/group as
> if it is being requeued after conuming a full slice. So may be we can divide
> it by some const number say 4 or something like that. This is a minor
> point though as this algorimthm will kind of evolve and we will learn
> what works best.
>
> Secondly, I think you wanted to SYNC vs ASYNC logic seem to be reversed.
> We would like to give ASYNC queues higher boost (Put these farther in
> tree) and lesser boost to SYNC queues. Looks like above constants will
> do the reverse?

Hi Vivek,

Currently, SYNC and ASYNC queues are in different service tree, they don't
impact each other. Here, I Really want use this logic.

Thanks,
Gui

>
>
> [..]
>> + if (RB_EMPTY_NODE(&cfqe->rb_node)) {
>> + /*
>> + * If this CFQ queue moves to another group, the original
>> + * vdisktime makes no sense any more, reset the vdisktime
>> + * here.
>> + */
>> + parent = rb_last(&service_tree->rb);
>> + if (parent) {
>> + u64 pos_offset;
>> +
>> + /*
>> + * Estimate the position according to its weight and
>> + * ioprio.
>> + */
>> + pos_offset = cfq_get_boost(cfqd, cfqq);
>> + /* Debug purpose, should remove. */
>> + cfq_log_cfqq(cfqd, cfqq, "pos_offset: %llu",
>> + pos_offset);
>
> You wanted to get rid of above debugging comment?
>
> Thanks
> Vivek
>

--
Regards
Gui Jianfeng


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