Ezequiel, Am 02.11.2014 um 22:52 schrieb Ezequiel Garcia: > Maybe you can explain a bit better what's this all about?
In short, blk-mq is the future and the current blk interface will be legacy. :-) Christoph asked me to convert the MTD block drivers to blk-mq. > Both the commit that introduces blk-mq and the paper on it talk about > high IOPS devices, multi-core, NUMA systems. I'm not sure this is the > case for UBI-based devices. > > Probably some numbers would help us decide. Does the patch increases the > dynamic memory footprint? Is there any performance benefit? I did a very rough micro benchmark: root@(none):~# dd if=/dev/ubiblock0_0 of=/dev/null bs=1M 121+1 records in 121+1 records out 127420416 bytes (127 MB) copied, 1.59056 s, 80.1 MB/s vs. root@(none):~# dd if=/dev/ubiblock0_0 of=/dev/null bs=1M 121+1 records in 121+1 records out 127420416 bytes (127 MB) copied, 0.916117 s, 139 MB/s So, yes there is a performance gain. > I kind of like the negative diffstat, but the code doesn't look cleaner > or simpler. > > In other words, we need a good reason before we agree on making this > "zen style" driver more complex. After reading my patch again I think we could move ubiblock_read_to_sg() to kapi.c or io.c. It is rather generic and maybe we can tun more UBI users to scattergather such that less vmalloc()s are needed. This would also make the diffstat nicer... Thanks, //richard
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