On Mo 18.Jan'10 at 12:14:43 -0600, Ravi Pinjala wrote: > On 01/18/10 11:17, Carlos R. Mafra wrote: > >Hi everyone, > > > >I am using btrfs for my /home partition since I upgraded my slow > >laptop hdd for an ssd 3 weeks ago. I am always in sync with Linus' > >tree of the day (plus a btrfs patch which is not in there yet) and > >so far I haven't lost any data, so all is good. > > > >I have a question about the write behavior of the various [btrfs- ] > >kernel threads, as I've been monitoring what is writing to the ssd > >just in case. > > > >So what I've been observing with 'iostat', 'iotop' and 'blktrace' > >is the following. If my laptop is almost absolutely idle (just > >a plain Window Maker and a few xterms and a couple dockapps open) > >there is nothing writing to the disk (which is OK). > > > >But as soon as I leave an open tab in chrome (or firefox) the various > >[btrfs- ] threads start writing in my /home, and I don't know what. > >For testing purposes, I mounted the config dir of chrome (~/.config/google-chrome) > >in my SD card (at /dev/mmcblk0p1) to exclude the possibility of maybe chrome > >trying to update its history or something, so that it does not write > >anything in my /home partition with btrfs. > > > >But I see this in the output of 'iotop' from a 60 sec interval, showing > >only the processes which wrote something: > > > >Total DISK READ: 0 B/s | Total DISK WRITE: 10.26 K/s > > PID USER DISK READ DISK WRITE SWAPIN IO COMMAND > > 485 root 0 B/s 5.19 K/s 0.00 % 0.02 % [btrfs-transacti] > > 3792 root 0 B/s 0 B/s 0.00 % 0.01 % [flush-btrfs-1] > > 476 root 0 B/s 0.13 K/s 0.00 % 0.00 % [btrfs-delalloc-] > > 481 root 0 B/s 4.93 K/s 0.00 % 0.00 % [btrfs-endio-wri] > > > >and there are more instances like this. Is there a way to avoid (or reduce) > >the writings of these threads? > > > >And when I start opening some pages in chrome and use it some more I > >get many many writes on my /home partition from these threads (and swapper, > >see below) even though I mounted the .config/google-chrome dir under > >/dev/mmcblk0p1 which uses ext4. > > > >>From another experiment where chrome was showing a blank tab a ~7 minutes > >run of 'blktrace -a write /dev/sda3' (sda3 is my /home) ends like this > >(from 'blkparse -s sda3.blktrace.0'): > > > - snip - > > Don't forget cache - should be under ~/.cache/google-chrome. That > would probably explain the disk activity you're seeing. Oh my... what a shame! That was it; I moved it to the SD card and now my ssd is not suffering anymore. Thanks a lot Ravi! -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
