On Wed, Sep 03, 2014 at 08:03:51AM +0200, john terragon wrote: > I tried the same routine on 32GB usb sticks. Same exact problems. 32GB > seems a bit much for a --mixed btrfs. > I haven't tried ssd_spread, maybe it's beneficial. However, as I wrote > above, disabling autodefrag gets rid completely of the "INFO: hung > task" messages but even though the kernel doesn't complain about > blocked kworkers, the rsync process still blocks for several minutes > throughout the whole copy.
It's very nice to know that you can reproduce it with autodefrag. I made a few analysis on the provided blocked stacks, the key is what blocks writing free space cache's pages to finish, it sits on wait_on_page_bit() which expects a WRITEBACK bit. Could you please paste the output of sysrq-w and sysrq-t when you get that hang? thanks, -liubo > > > On Wed, Sep 3, 2014 at 4:44 AM, Chris Murphy <[email protected]> wrote: > > > > On Sep 2, 2014, at 12:40 AM, Duncan <[email protected]> wrote: > >> > >> Mkfs.btrfs used to default to 4 KiB node/leaf sizes; now days it defaults > >> to 16 KiB as that's far better for most usage. I wonder if USB sticks > >> are an exception... > > > > USB sticks > 1 GB get 16KB nodesize also. At <= 1 GB, mixed-bg is default > > as is 4KB nodesize. Probably because queue/rotational is 1 for USB sticks, > > they mount without ssd or ssd_spread which may be unfortunate (I haven't > > benchmarked it but I suspect ssd_spread would work well for USB sticks). > > > > It was suggested a while ago that maybe mixed-bg should apply to larger > > volumes, maybe up to 8GB or 16GB? > > > > > > Chris Murphy > > > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > > the body of a message to [email protected] > > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
