On 2015-12-17 11:29, Johannes Berg wrote: > On Thu, 2015-12-17 at 10:20 +0100, Janusz Dziedzic wrote: >> HW/driver should set NEED_ALIGNED4_SKBS flag in case require >> aligned skbs to four-byte boundaries. >> >> Before we have to do memmove() in the driver before >> pass this to HW and memmove() back in tx completion. >> This patch allow to save CPU and skip such memmoves. > > Can you quantify that btw? It shouldn't be that expensive since it's > all in the cache for read, so just has to be written out to RAM before > the DMA can happen... On many devices that I'm using, the data path is definitely too bloated for the packet to still be in cache, so I do think this will help. Remember, having only 32 KiB Dcache (no L2) is not uncommon on devices running ath9k. > And on status it will be pulled into the cache > anyway, and you don't even need the write to happen before you can > continue. This doesn't make sense to me. The write needs to happen before the device can do DMA... - Felix -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
