Messages in this thread | | | Date | Sun, 02 Nov 2014 19:27:54 -0300 | From | Ezequiel Garcia <> | Subject | Re: [PATCH] UBI: Block: Add blk-mq support |
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On 11/02/2014 07:21 PM, Richard Weinberger wrote: > 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. >
Ah, OK. That makes sense then.
>> 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. >
Wow. Where did you run this and on top of what storage device?
I'm still interested in the memory footprint, UBI is already heavy enough.
>> 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... >
Yes, any additional effort to make the current patch any simpler would be great. In its current form it seems rather cumbersome to me.
If you can re-submit something better and put a more verbose commit log, I'd really appreciate it :) -- Ezequiel García, Free Electrons Embedded Linux, Kernel and Android Engineering http://free-electrons.com
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