From: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>,
Corrado Zoccolo <czoccolo@gmail.com>,
Chad Talbott <ctalbott@google.com>,
Nauman Rafique <nauman@google.com>,
Divyesh Shah <dpshah@google.com>,
linux kernel mailing list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 5/8 v2] cfq-iosched: Introduce hierarchical scheduling with CFQ queue and group at the same level
Date: Tue, 14 Dec 2010 14:09:33 +0800 [thread overview]
Message-ID: <4D070A1D.4060904@cn.fujitsu.com> (raw)
In-Reply-To: <20101214034914.GA8713@redhat.com>
Vivek Goyal wrote:
...
>> -static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd)
>> +static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
>> {
>> - struct cfq_rb_root *st = &cfqd->grp_service_tree;
>> - struct cfq_group *cfqg;
>> - struct cfq_entity *cfqe;
>> + struct cfq_rb_root *st;
>> + unsigned count;
>>
>> - if (RB_EMPTY_ROOT(&st->rb))
>> - return NULL;
>> - cfqe = cfq_rb_first_entity(st);
>> - cfqg = cfqg_of_entity(cfqe);
>> - BUG_ON(!cfqg);
>> - update_min_vdisktime(st);
>> - return cfqg;
>> + if (!cfqg) {
>> + cfqd->serving_prio = IDLE_WORKLOAD;
>> + cfqd->workload_expires = jiffies + 1;
>> + return;
>> + }
>
> I am wondering where do we use above code. Do we ever call
> choose_service_tree() with cfqg == NULL? Can't seem to figure out by
> looking at the code.
>
Vivek,
This piece of code comes from original CFQ code. Think more about it, this
piece of code seems redundant. When cfq_choose_cfqg() is called in select_queue(),
there must be at least one backlogged CFQ queue waiting for dispatching, hence
there must be at least one backlogged CFQ group on service tree. So we never call
choose_service_tree() with cfqg == NULL.
I'd like to post a seperate patch to get rid of this piece.
Thanks,
Gui
next prev parent reply other threads:[~2010-12-14 6:09 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <4CDF7BC5.9080803@cn.fujitsu.com>
[not found] ` <4CDF9CD8.8010207@cn.fujitsu.com>
[not found] ` <20101115193352.GB3396@redhat.com>
2010-11-29 2:32 ` [RFC] [PATCH 3/8] cfq-iosched: Introduce vdisktime and io weight for CFQ queue Gui Jianfeng
[not found] ` <4CDF9CE0.3060606@cn.fujitsu.com>
[not found] ` <20101115194855.GC3396@redhat.com>
2010-11-29 2:34 ` [RFC] [PATCH 4/8] cfq-iosched: Get rid of st->active Gui Jianfeng
[not found] ` <4CDF9D06.6070800@cn.fujitsu.com>
[not found] ` <20101115195428.GE3396@redhat.com>
2010-11-29 2:35 ` [RFC] [PATCH 7/8] cfq-iosched: Enable deep hierarchy in CGgroup Gui Jianfeng
[not found] ` <4CDF9D0D.4060806@cn.fujitsu.com>
[not found] ` <20101115204459.GF3396@redhat.com>
2010-11-29 2:42 ` [RFC] [PATCH 8/8] cfq-iosched: Introduce hierarchical scheduling with CFQ queue and group at the same level Gui Jianfeng
2010-11-29 14:31 ` Vivek Goyal
2010-11-30 1:15 ` Gui Jianfeng
[not found] ` <4CDF9CC6.2040106@cn.fujitsu.com>
[not found] ` <20101115165319.GI30792@redhat.com>
[not found] ` <4CE2718C.6010406@kernel.dk>
2010-12-13 1:44 ` [PATCH 0/8 v2] Introduce CFQ group hierarchical scheduling and "use_hierarchy" interface Gui Jianfeng
2010-12-13 13:36 ` Jens Axboe
2010-12-14 3:30 ` Gui Jianfeng
2010-12-13 14:29 ` Vivek Goyal
2010-12-14 3:06 ` Gui Jianfeng
2010-12-14 3:29 ` Vivek Goyal
[not found] ` <4D01C6AB.9040807@cn.fujitsu.com>
2010-12-13 1:44 ` [PATCH 1/8 v2] cfq-iosched: Introduce cfq_entity for CFQ queue Gui Jianfeng
2010-12-13 15:44 ` Vivek Goyal
2010-12-14 1:30 ` Gui Jianfeng
2010-12-13 1:44 ` [PATCH 2/8 v2] cfq-iosched: Introduce cfq_entity for CFQ group Gui Jianfeng
2010-12-13 16:59 ` Vivek Goyal
2010-12-14 1:33 ` Gui Jianfeng
2010-12-14 1:47 ` Gui Jianfeng
2010-12-13 1:44 ` [PATCH 3/8 v2] cfq-iosched: Introduce vdisktime and io weight for CFQ queue Gui Jianfeng
2010-12-13 16:59 ` Vivek Goyal
2010-12-14 2:41 ` Gui Jianfeng
2010-12-14 2:47 ` Vivek Goyal
2010-12-13 1:44 ` [PATCH 4/8 v2] cfq-iosched: Extract some common code of service tree handling for CFQ queue and CFQ group Gui Jianfeng
2010-12-13 22:11 ` Vivek Goyal
2010-12-13 1:45 ` [PATCH 5/8 v2] cfq-iosched: Introduce hierarchical scheduling with CFQ queue and group at the same level Gui Jianfeng
2010-12-14 3:49 ` Vivek Goyal
2010-12-14 6:09 ` Gui Jianfeng [this message]
2010-12-15 7:02 ` Gui Jianfeng
2010-12-15 22:04 ` Vivek Goyal
2010-12-13 1:45 ` [PATCH 6/8] blkio-cgroup: "use_hierarchy" interface without any functionality Gui Jianfeng
2010-12-15 21:26 ` Vivek Goyal
2010-12-16 2:42 ` Gui Jianfeng
2010-12-16 15:44 ` Vivek Goyal
2010-12-17 3:06 ` Gui Jianfeng
2010-12-17 23:03 ` Vivek Goyal
2010-12-13 1:45 ` [PATCH 7/8] cfq-iosched: Add flat mode and switch between two modes by "use_hierarchy" Gui Jianfeng
2010-12-20 19:43 ` Vivek Goyal
2010-12-13 1:45 ` [PATCH 8/8] blkio-cgroup: Document for blkio.use_hierarchy Gui Jianfeng
2010-12-13 15:10 ` Vivek Goyal
2010-12-14 2:52 ` Gui Jianfeng
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