On Thu, Apr 24, 2014 at 2:54 AM, Stefan Ring <stefanrin@xxxxxxxxx> wrote: > I've become interested in this topic, as I'm also running MySQL with > O_DIRECT and innodb_file_per_table. Out of curiosity, I immediately > ran xfs_bmap on a moderately sized table space (34GB). It listed > around 30000 fragments, on average one for every MB. > > I want to report what happened then: A flurry of activity started on > both disks (root/swap lives on one of them, the data volume containing > the MySQL files on another) and lasted for about two minutes. > Afterwards, all memory previously allocated to the file cache has > become free, and also everything XFS seems to keep buffered internally > (I think it's called SReclaimable) was released. Swap usage increased > only slightly. dmesg was silent during that time. > > This is a 2.6.32-358.2.1.el6.x86_64 kernel with xfsprogs 3.1.1 (CentOS > 6.4). The machine has 64GB of RAM (2 NUMA nodes) and 24 (virtual) > cores. Is this known behavior of xfs_bmap? Interesting...it looks like your box flushed all of the OS buffer cache. I am unable to reproduce this behavior on my test box with the 3.10.37 kernel. I also tried with 2.6.32-358.18.1.el6.x86_64 and didn't hit the issue, but obviously our access patterns differ wildly. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
