On 06/18/2017 10:30 AM, Jeff Layton wrote: > I've run across a regression from v4.11. If I boot a v4.12-rc1 or later > kernel, make a large brd device and try to format it, it quickly slows > down to a crawl and then the OOM killer kicks in. > > I ran a bisect and it landed here: > > commit f09a06a193d942a12c1a33c153388b3962222006 (HEAD, refs/bisect/bad) > Author: Christoph Hellwig <h...@lst.de> > Date: Wed Apr 5 19:21:16 2017 +0200 > > brd: remove discard support > > It's just a in-driver reimplementation of writing zeroes to the pages, > which fails if the discards aren't page aligned. > > Signed-off-by: Christoph Hellwig <h...@lst.de> > Reviewed-by: Hannes Reinecke <h...@suse.com> > Signed-off-by: Jens Axboe <ax...@fb.com> > > > I've been reproducing it in a VM with ~8G allocated to it: > > I have a modprobe.d file with this in it: > > options brd rd_nr=1 rd_size=1073741824 > > I then just: > > # modprobe brd > # mkfs -t ext2 /dev/ram0 > > It keels over pretty quickly after that.
Just checked, and creating a 1TB ram disk and then running mkfs.ext2 on it writes 16851MiB of data. I can't say I'm surprised you OOM, if you run that in a 8G VM, as you're about 8G short. I'm puzzled as to why the discard change would make any difference, however. -- Jens Axboe
