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Patches Published Again For Replacing Linux Kernel's CFQ With BFQ

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  • #11
    Originally posted by Beherit View Post
    Just last week I switched on blk-mq. I'm not entirely sure what it is or if it replaces or works as a layer above/below CFS/BFQ/noop/deadline, but my subjective experience so far is a more responsive system and shorter loading times when using an SSD, compared to using deadline without blk-mq.
    How did you switch to blk-mq?

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    • #12
      Originally posted by fackamato View Post

      How did you switch to blk-mq?
      I added "scsi_mod.use_blk_mq=1" to the kernel parameters as per the instructions here: https://wiki.archlinux.org/index.php..._IO_schedulers

      It's the first place I ever saw blk-mq mentioned, I searched for it but only found very technical explanations and server benchmarks. But not much besides some old benchmarks made on a laptop on how it affects performance overall.

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      • #13
        Originally posted by jakubo View Post
        isnt this a benchmark site...? o.O just saying :P
        Give this man a cookie!

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        • #14
          You don't want blk-mq enabled if you have HDDs in your system: http://thread.gmane.org/gmane.linux.kernel/2089172

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          • #15
            Originally posted by Beherit View Post
            I added "scsi_mod.use_blk_mq=1" to the kernel parameters as per the instructions here: https://wiki.archlinux.org/index.php..._IO_schedulers

            It's the first place I ever saw blk-mq mentioned, I searched for it but only found very technical explanations and server benchmarks. But not much besides some old benchmarks made on a laptop on how it affects performance overall.
            There no point in using block mq unless you're using the nvme protocol. At a minimum that means no hdd. More practically it means that you have single ssds that get read performances over 1GB/s. In that case, it can help... but probably not with desktop loads.
            LWN wrote an excellent article about this features when it was being merged.

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            • #16
              I've been using BFQ for some months and I have to say it has an incredible impact on both my notebooks. I have two slow 5400 RPM disks and when using bitcoind, dropbox and owncloud client they where sluggish as hell. With BFQ in place everything always run smoothly. I haven't made any benchmarks about boot time and such, but the day by day experience is greatly improved by this scheduler.

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              • #17
                Originally posted by yoshi314 View Post

                when confronted with :



                makes me suspicious about how exactly the benchmarks were performed, as many youtube demos did switch schedulers on the fly. If the dumbed down cfq was used as comparison, no wonder bfq appears to be so great.

                I didn't poke through the code yet, though. Just running on paranoia atm.
                That message just means that his patchset slowly converts CFQ into BFQ. Instead of adding a new scheduler to the kernel, he wants to change CFQ from the inside out. I don't think it has anything to do with the demos.

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