From mboxrd@z Thu Jan 1 00:00:00 1970 From: Juha Aatrokoski Subject: Re: bcache hangs on writes, recovers after disabling discard on cache device Date: Thu, 11 Jul 2013 17:58:17 +0300 (EEST) Message-ID: References: <51C891C9.4060809@modelnine.org> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Return-path: In-Reply-To: <51C891C9.4060809-EqIAFqbRPK3NLxjTenLetw@public.gmane.org> Sender: linux-bcache-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Heiko Wundram Cc: linux-bcache-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-bcache@vger.kernel.org On Mon, 24 Jun 2013, Heiko Wundram wrote: > In a rather old thread of mine (514C4FC1.6090804-EqIAFqbRPK3NLxjTenLetw@public.gmane.org), I already > stated a problem I was seeing back at the time, namely that bcache seems to > hang on writes to the SSD device after some time, writing 50 MB/s continuously > to the output device. ... > Disabling discard on the SSD device (by echo 0 > > /sys/fs/bcache/.../cache0/discard) makes the bcache device become responsive > again. I can confirm this. On Monday I booted into kernel 3.8.13-gentoo with the current "bcache" branch patched onto it. Discard was on for the cache device, and today this 50MB/s hang occured. Disabling discard did indeed fix it. I had CONFIG_BCACHE_CLOSURES_DEBUG=y in the kernel, and the contents of /sys/kernel/debug/bcache/bcache-UUID and /sys/kernel/debug/closures both before and after disabling discard can be found at the address below, in case they can help in determining where exactly the hang happens. http://www.metsahovi.fi/~jha/bcache/