From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Stancek Date: Wed, 1 Feb 2017 05:59:38 -0500 (EST) Subject: [LTP] [PATCH] [RFC] zram01: Fix on ppc64le In-Reply-To: <20170201094541.GA13898@rei.lan> References: <1485870273-26990-1-git-send-email-chrubis@suse.cz> <845142934.836828.1485879246140.JavaMail.zimbra@redhat.com> <20170201094541.GA13898@rei.lan> Message-ID: <1372516698.1369615.1485946778720.JavaMail.zimbra@redhat.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ltp@lists.linux.it ----- Original Message ----- > From: "Cyril Hrubis" > To: "Jan Stancek" > Cc: ltp@lists.linux.it > Sent: Wednesday, 1 February, 2017 10:45:41 AM > Subject: Re: [LTP] [PATCH] [RFC] zram01: Fix on ppc64le > > Hi! > > This is ~4 years old comment from Zach Brown, when I hit an issue on ppc, > > where I could alloc only 1/2 of the volume size: > > > > "That small volume mkfs warning is issued for devices less than a gig. It > > indicates that btrfs has gone in to a weird degenerate allocation scheme. > > We'd only support volumes much larger than that, though I have no quick > > rule to say how large starts to be reasonable. Multiple gig, certainly." > > > > I'm running with 384M since then, so far successfully. If we don't allocate > > too much data on it, we might be OK, but still I'd go with minimum default > > of 256M. > > What exactly do you have in mind? Using 256MB by default for any Btrfs > filesystem or fallback to 256MB if mkfs.btrfs output cannot be parsed? I meant default size. > > I guess that for any other testcase it would be fine enough to bump the > minimal device size to 256MB unconditionally, but in this case we create > the data in RAM albeit compressed, and so I would like to keep it as > small as possible, since otherwise it may fail on embedded hardware. I didn't have a look at zram01, but can't we detect this and TCONF? We can try with minimum and see how frequently it changes, I just wanted to share Zach's quote and my experience with tiny btrfs volumes. Regards, Jan > Maybe we should just remove Btrfs from the zram01.sh test so that we > don't have to keep bumping the minimal size each time the minimal Btrfs > size calculation changes... > > -- > Cyril Hrubis > chrubis@suse.cz >