On Mon, Dec 14, 2015 at 10:08:16AM +0800, Qu Wenruo wrote: > > > Martin Steigerwald wrote on 2015/12/13 23:35 +0100: > >Hi! > > > >For me it is still not production ready. > > Yes, this is the *FACT* and not everyone has a good reason to deny it. > > >Again I ran into: > > > >btrfs kworker thread uses up 100% of a Sandybridge core for minutes on random > >write into big file > >https://bugzilla.kernel.org/show_bug.cgi?id=90401 > > Not sure about guideline for other fs, but it will attract more dev's > attention if it can be posted to maillist. > > > > > > >No matter whether SLES 12 uses it as default for root, no matter whether > >Fujitsu and Facebook use it: I will not let this onto any customer machine > >without lots and lots of underprovisioning and rigorous free space > >monitoring. > >Actually I will renew my recommendations in my trainings to be careful with > >BTRFS. > > > > From my experience the monitoring would check for: > > > >merkaba:~> btrfs fi show /home > >Label: 'home' uuid: […] > > Total devices 2 FS bytes used 156.31GiB > > devid 1 size 170.00GiB used 164.13GiB path /dev/mapper/msata-home > > devid 2 size 170.00GiB used 164.13GiB path /dev/mapper/sata-home > > > >If "used" is same as "size" then make big fat alarm. It is not sufficient for > >it to happen. It can run for quite some time just fine without any issues, > >but > >I never have seen a kworker thread using 100% of one core for extended period > >of time blocking everything else on the fs without this condition being met. > > > > And specially advice on the device size from myself: > Don't use devices over 100G but less than 500G. > Over 100G will leads btrfs to use big chunks, where data chunks can be at > most 10G and metadata to be 1G. > > I have seen a lot of users with about 100~200G device, and hit unbalanced > chunk allocation (10G data chunk easily takes the last available space and > makes later metadata no where to store)
Maybe we should tune things so the size of the chunk is based on the space remaining instead of the total space? > > And unfortunately, your fs is already in the dangerous zone. > (And you are using RAID1, which means it's the same as one 170G btrfs with > SINGLE data/meta) > > > > >In addition to that last time I tried it aborts scrub any of my BTRFS > >filesstems. Reported in another thread here that got completely ignored so > >far. I think I could go back to 4.2 kernel to make this work. We'll pick this thread up again, the ones that get fixed the fastest are the ones that we can easily reproduce. The rest need a lot of think time. -chris -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
