Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9048621903
Date:   Mon, 13 Nov 2017 11:58:30 -0800
From:   Shaohua Li <shli@kernel.org>
To:     Tejun Heo <tj@kernel.org>
Cc:     axboe@kernel.dk, linux-kernel@vger.kernel.org, kernel-team@fb.com,
        lizefan@huawei.com, hannes@cmpxchg.org, cgroups@vger.kernel.org,
        guro@fb.com
Subject: Re: [PATCH 7/7] blk-throtl: don't throttle the same IO multiple times
Message-ID: <20171113195830.ij3god7gdrj4u4ax@kernel.org>
References: <20171112222613.3613362-1-tj@kernel.org>
 <20171112222613.3613362-8-tj@kernel.org>
 <20171113040716.kaheegc4qub42n6z@kernel.org>
 <20171113111348.GF983427@devbig577.frc2.facebook.com>
 <20171113155745.GI983427@devbig577.frc2.facebook.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20171113155745.GI983427@devbig577.frc2.facebook.com>
User-Agent: NeoMutt/20170609 (1.8.3)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Mon, Nov 13, 2017 at 07:57:45AM -0800, Tejun Heo wrote:
> Hello,
> 
> On Mon, Nov 13, 2017 at 03:13:48AM -0800, Tejun Heo wrote:
> > You're right.  If we wanna take this approach, we need to keep the
> > throttled flag while cloning.  The clearing part is still correct tho.
> > Without that, I get 1/4 bw limit enforced.  Hmm... I'm not quite sure
> > where that 1/4 is coming from tho.  Will investigate more.
> 
> Okay, this is because when we spiit, the split bio is the first part
> which gets issued and then the orignal bio is wound forward and
> requeued.  So, for the splits, the original bio is the one which gets
> trimmed in the front and requeued, so not clearing BIO_THROTTLED is
> enough.  I think we should still copy BIO_THROTTLED on clones so that
> we don't get suprises w/ other bio drivers.

Oh, I think there is a better solution. Not adding a new bdev is possible. We
always set the BIO_THROTTLED flag after block-throttle and copy the flag in
clone. In bio_set_dev, we clear the flag. This should work I think.

Thanks,
Shaohua

From 1583982028360286738@xxx Mon Nov 13 19:56:18 +0000 2017
X-GM-THRID: 1583901042028495922
X-Gmail-Labels: Inbox,Category Forums,HistoricalUnread