From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jack Wang Subject: Re: bcache strange behaviour in write back mode Date: Mon, 22 Apr 2013 22:27:03 +0200 Message-ID: <51759D17.5040204@profitbricks.com> References: <51758C42.4040708@profitbricks.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: Sender: linux-bcache-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Kent Overstreet Cc: "linux-bcache-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Kent Overstreet , dongsu.park-EIkl63zCoXaH+58JC4qpiA@public.gmane.org List-Id: linux-bcache@vger.kernel.org On 2013=E5=B9=B404=E6=9C=8822=E6=97=A5 22:19, Kent Overstreet wrote: > So you can easily reproduce this? If so, that's _awesome_ news - woul= d > you be willing to try out a debug kernel with some tracing stuff adde= d? > Maybe we can finally nail this. >=20 >=20 Thanks for reply, Kent, two of my colleagues saw this behaviour, so I think we can reproduce this. If you could give me more detailed guide to narrow it down, I can try i= t on my side. Regards, Jack > On Mon, Apr 22, 2013 at 12:15 PM, Jack Wang > wrote: >=20 > Hi all, >=20 > We've seen strange behaviour in bcache mode in current bcache-tes= ting > branch with Possible allocator fix: >=20 > Once I start writing data with "dd if=3D/dev/zero of=3D/dev/bcach= e0 bs=3D4k > count=3D10000 oflag=3Dsync", all SSDs in the Pool go close to 100= % util and > I see about 3600 writes/second in iostat for each disk in the poo= l, BUT > no data written in means of throughput. >=20 > Then after some seconds (the flush interval of bcache) I see the = flush > of the writeback and also data written to the pool SSDs which loo= ks > pretty much like reordering and merging happened for that data. >=20 > bcache-3.2 does not have such problem. > only bcache(master) and bcache-testing have such problem. >=20 > What's the possible reason? >=20 > Regards, > Jack > -- > To unsubscribe from this list: send the line "unsubscribe > linux-bcache" in > the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > > More majordomo info at http://vger.kernel.org/majordomo-info.htm= l >=20 >=20