Hi Linus, On Tuesday 15 May 2018 06:09 PM, Linus Walleij wrote: > On Mon, May 14, 2018 at 1:30 PM, Faiz Abbas <faiz_abbas@xxxxxx> wrote: > >> Also, I see many times the number of interrupts for mmc1 in 4.14. > (...) >> I also printed out the size of the DMA transfers in the omap_hsmmc >> driver during the dd command. I see that the maximum size of the dma >> transfer has decreased from 1 MB to 256kB between 4.13 and 4.14. > > This seems like my fault for removing the bounce buffer. > (The name bounce buffer is misleading, I suspect the right > term for what is was doing was "merge buffer" or something, > coalescing physically consecutive requests.) > > commit de3ee99b097dd51938276e3af388cd4ad0f2750a > "mmc: Delete bounce buffer handling" > should be the culprit. I don't think so. I checked out to the commit before that and see that the interrupts are still too high. > > The bounce buffer only makes any performance impact if the > host DMA controller is unable to handle scatter-gather lists > so the number of segments is set down to 1. > > Can you verifty that: > - mmc->max_segs == 1 No. It is 64 in v4.14. It was 1024 in v4.13. v4.14 https://pastebin.ubuntu.com/p/4wXB2jb6zw/ v4.13 https://pastebin.ubuntu.com/p/dpd6kb4YJY/ > - You were previously enabling CONFIG_MMC_BLOCK_BOUNCE Yes. Regards, Faiz -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
