On 06/15/2015 03:29 PM, David Sterba wrote: > On Mon, Jun 15, 2015 at 02:47:24PM +0200, Tovo Rabemanantsoa wrote: >> Hi all, >> By browsing this list's archive, I've found a thread initiated by >> Charles Cazabon entitled: "Oddly slow read performance with near-full >> largish FS." >> Actually, I'm living the same experience but with a not so large FS >> (256GB on a SSD). Indeed, when I have less than 1GB of free space, the >> applications (thunderbird, thunar ...) on the machine become awfully >> slow but remain normal if I make some cleaning. >> Is it due to the FS or because it's an SSD hard disk ? > > 1G of 256G is less than a percent. At this level of usage you can expect > slowdown on any filesystem. > > This could be caused by free space fragmentation and even on a SSD, this > needs extra time to process. Higher number of fragments needs more > structures to represent them and cost more CPU time, though this still > might not be the worst impact. > > AFAIK btrfs space handling logic needs to do more flushes of unwritten > data when the accounted free space goes below some threshold (because > COW needs to write the data twice before it switches to the new "root" > pointer and can free the previous version).
Thanks for you reply, If I really understand, it's always a good idea to keep more than 1% of free space. Right ? -- 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
