On Mon, Jan 20, 2014 at 10:03:48PM +0000, Wei Liu wrote: [...] > > You beat me to this. Was about to reply to your other email. :-) > > It's also worth mentioning that DIV_ROUND_UP part is merely estimation, > as you cannot possible know the maximum / miminum queue length of all > other vifs (as they can be changed during runtime). In practice most > users will stick with the default, but some advanced users might want to > tune this value for individual vif (whether that's a good idea or not is > another topic). > > So, in order to convince myself this is safe. I also did some analysis > on the impact of having queue length other than default value. If > queue_len < XENVIF_QUEUE_LENGTH, that means you can queue less packets > in qdisc than default and drain it faster than calculated, which is > safe. On the other hand if queue_len > XENVIF_QUEUE_LENGTH, it means > actually you need more time than calculated. I'm in two minded here. The > default value seems sensible to me but I'm still a bit worried about the > queue_len > XENVIF_QUEUE_LENGTH case. > > An idea is to book-keep maximum tx queue len among all vifs and use that > to calculate worst scenario. >
And unfortunately there doesn't seem to be a way to know when tx queue length is changed! So this approach won't work. :-( Wei. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
