31.08.2020 18:08, Adrian Hunter пишет: > On 27/08/20 12:36 pm, Dmitry Osipenko wrote: >> 27.08.2020 09:45, Adrian Hunter пишет: >>> On 27/08/20 9:07 am, Dmitry Osipenko wrote: >>>> Hello! >>>> >>>> I was debugging WiFi performance problems on Acer A500 tablet device >>>> that has BCM4329 WiFi chip which is connected to NVIDIA Terga20 SoC via >>>> SDIO and found that the following commit causes a solid 5-10 Mbit/s of >>>> WiFi throughput regression after 5.2 kernel: >>> >>> What is that in percentage terms? >> >> That is about 20%. >> >>>> commit c07a48c2651965e84d35cf193dfc0e5f7892d612 >>>> Author: Adrian Hunter <adrian.hunter@xxxxxxxxx> >>>> Date: Fri Apr 5 15:40:20 2019 +0300 >>>> >>>> mmc: sdhci: Remove finish_tasklet >>>> >>>> Remove finish_tasklet. Requests that require DMA-unmapping or >>>> sdhci_reset >>>> are completed either in the IRQ thread or a workqueue if the >>>> completion is >>>> not initiated by the IRQ. >>>> >>>> Reverting the offending commit on top of recent linux-next resolves the >>>> problem. >>>> >>>> Ulf / Adrian, do you have any ideas what could be done in regards to >>>> restoring the SDIO performance? Should we just revert the offending commit? >>>> >>> >>> Unfortunately I think we are past the point of returning to the tasklet. >>> >>> sdhci can complete requests in the irq handler but only if ->pre_req() and >>> ->post_req() are used, which is not supported by SDIO at present. pre_req >>> and post_req were introduced to reduce latency for the block driver, so it >>> seems reasonable perhaps to look at using them in SDIO as well. >>> >> >> I'll try to take a look at pre/post_req(), but I'm not very familiar >> with the MMC code, so it may take quite some time. Will be great if you >> could help with making a patch that I could test! >> > > You could start by seeing if using pre/post_req helps at all, as below. > If that doesn't help, then it might need more analysis. Hello, Adrian! I tested yours patch and 100% fixes the problem! Thank you very much! Please make a proper patch and feel free to add my t-b! Tested-by: Dmitry Osipenko <digetx@xxxxxxxxx>
