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Groups > linux.kernel > #1668668
| From | Jens Axboe <axboe@kernel.dk> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: attempting to format brd device results in OOM kills |
| Date | 2017-06-19 00:30 +0200 |
| Message-ID | <tTQRH-2AF-9@gated-at.bofh.it> (permalink) |
| References | <tTLp2-7x8-49@gated-at.bofh.it> <tTQRH-2AF-1@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On 06/18/2017 04:21 PM, Jens Axboe wrote: > 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 <hch@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 <hch@lst.de> >> Reviewed-by: Hannes Reinecke <hare@suse.com> >> Signed-off-by: Jens Axboe <axboe@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. Reverted the patch, and I see identical behavior. The only difference is that the whole device is trimmed first, as expected. But it still writes ~16G afterwards. Are you sure this commit is what broke things for you? Honestly, I don't see how it could ever work with 1TB ram disk, 8G of RAM, and 16G of data written. -- Jens Axboe
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Re: attempting to format brd device results in OOM kills Jens Axboe <axboe@kernel.dk> - 2017-06-19 00:30 +0200
Re: attempting to format brd device results in OOM kills Jens Axboe <axboe@kernel.dk> - 2017-06-19 00:30 +0200
Re: attempting to format brd device results in OOM kills Jeff Layton <jlayton@redhat.com> - 2017-06-19 00:50 +0200
Re: attempting to format brd device results in OOM kills Jens Axboe <axboe@kernel.dk> - 2017-06-19 03:50 +0200
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