W dniu 29.03.2016 o 13:17, Kent Overstreet pisze: > On Tue, Mar 29, 2016 at 12:41:27PM +0200, Marcin Mirosław wrote: >> Hi! >> >> Because I don't know what features should work I think it's better to >> report a bug than do nothing. >> I created fs, mounted, then I changed compression (via sysfs) to lz4. >> Next I copied portage tree to filesystem. Then I started to think why >> "compression_stats" shows that data are compressed but `df` shows values >> that looks like data are uncompressed: >> cat compression_stats >> uncompressed data: >> nr extents: 1976 >> size (bytes): 1784832 >> compressed data: >> nr extents: 282264 >> compressed size (bytes): 346365952 >> uncompressed size (bytes): 6398948352 > > Yeah, I don't have the code yet to distinguish between compressed/uncompressed > size in the various usage stuff. It's coming. Ok, thanks for info. >> df -h: >> Filesystem Size Used Avail Use% Mounted on >> /dev/mapper/system10-bcacheportage 4.0G 4.0G 82M 99% /usr/portage >> >> So I started to create file filled with zeroes: `dd if=/dev/zero >> of=/path/file bs=1M". I filled up filesystem. Then I run `emerge` and I >> got I/O error. In dmesg I see: >> >> [ 4466.898819] kworker/u8:0: page allocation failure: order:4, >> mode:0x2404000 > > The lz4 code is unfinished - as you can see it doesn't gracefully handle memory > allocation failures yet. The gzip compression code does handle allocation > failures, but won't get as good a compression ratio (because it's doing the > compression in smaller chunks). > > At some point I need to dig into the lz4 code and come up with a version that > doesn't require contiguous buffers, but that's going to be difficult. > >> Accesing this file with zeroes throws I/O error, it looks that other >> files are accesible. After removing this file with zeroes free space is >> not returned. > > Odd.. probably something to do with how the pagecache handles IO errors, I'm > guessing. When I did test with filling up free space and I didn't had I/O error then free space was calculated correctly. > You should have been able to still read the data later (after clearing the error > in the pagecache somehow, a drop_caches might do it). > > I'll bump the lz4 stuff higher up on the list, I want to use it myself. Great! gzip is slow for me (at least used with zfs). Thanks, Marcin -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
