On Thu, 20 May 2010, Linus Torvalds wrote: > Are there actual real loads that get improved? I don't care if it means > that the improvement goes from three orders of magnitude to just a couple > of percent. The "couple of percent on actual loads" is a lot more > important than "many orders of magnitude on a made-up benchmark". The reason I've been looking at zero copy for fuse is that embedded people have been complaining about fuse's large CPU overhead for I/O. So large in fact that it was having a performance impact even for relatively slow devices. And most of that overhead comes from copying data around. So it's not the 20GB/s throughput that's interesting but the reduced CPU overhead, especially on slower processors. Apart from cache effects 20GB/s throughput with a null filesystem means 1% CPU at 200MB/s transfer speed with _any_ filesystem. Without bigger requests that translates to 4% overhead and without zero copy about 15%. That's on a core2/1.8GHz, with an embedded CPU the overhead reduction would be even more significant. Miklos -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>