Jens Axboe wrote: > On Thu, Jan 29 2009, Alan D. Brunelle wrote: >> Has anybody experimented with increasing the _number_ of buffers rather >> than the _size_ of the buffers when confronted with drops? I'm finding >> on a large(ish) system that it is better to have lots of small buffers >> handled by relay rather than fewer larger buffers. In my particular case: >> >> 16 CPUs >> 96 devices >> running some dd's against all the devices... >> >> -b 1024 or -b 2048 still results in drops >> >> but: >> >> -n 512 -b 16 allows things to run smoother. >> >> I _think_ this may have to do with the way relay reports POLLIN: it does >> it only when a buffer switch happens as opposed to when there is data >> ready. Need to look at this some more, but just wondering if others out >> there have found similar things in their testing... > > That's interesting. The reason why I exposed both parameters was mainly > that I didn't have the equipment to do adequate testing on what would be > the best setup for this. So perhaps we can change the README to reflect > that it is usually better to bump the number of buffers instead of the > size, if you run into overflow problems? > It's not clear - still running tests. [I know for SMALLER numbers of disks increasing the buffers has worked just fine.] I'm still fighting (part time) with version 2.0 of blktrace, so _that_ may have something to do with it! :-) Alan -- To unsubscribe from this list: send the line "unsubscribe linux-btrace" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
