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Linux Zcache Now Handles Crypto Compression

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  • Linux Zcache Now Handles Crypto Compression

    Phoronix: Linux Zcache Now Handles Crypto Compression

    Seth Jennings of IBM has provided a patch for the next Linux kernel that removes the LZO-specific compression bits inside zcache and instead hooks this compressed page cache into the generic Crypto compression API...

    http://www.phoronix.com/vr.php?view=MTAzNjM

  • #2
    zCache if for "home" usage? if so can we have benchmark about it, dear phoronix?

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    • #3
      I'm currently finding myself more pressed for RAM than CPU. I hadn't heard of zcache before so I might try it out.

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      • #4
        I wonder if Android has adopted this?
        If not, hopefully CM has/will do so. This would help tremendously with devices with <=512MB.
        However, if the damn SoC would start putting sata connectors on these devices so we could use storage that gets decent I/O we wouldn't need it.
        These current storage devices are slow as hell. Sure, they're cheap, but why hasn't, say, Apple (who is supposed to be premium) done something about this situation? Can you imagine how much it would lower game load times?
        Sure, you could use that high bandwidth SD card standard (is it SD or the other one?) but that seems to only be available on some phones, and I'm not sure how fast that is b/c SD cards typically suck as well.
        Supposedly, part of the reason is that manufacturors use cheap, 3 bits/cell flash. Certainly moving to at least 2bit/cell (though SLC makes more sense to me considering the size of these drives and how much writing they endure) would be worth the tradeoff in size/price for the performance gain?

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        • #5
          CyanogenMod has ZCache option, but its disabled by default on newer phones. It worked great (from what I hear) on the older G1 (256MB), but with the newer phones, it caused instability or something to that effect, which is why it was disabled.

          It would be interesting to see this issue explored further by Phoronix. Benchmarks of different systems with different amount of RAM with and without a Mechanical Hard Drive would be interesting to see!

          Even enabling Z-Cache on the Pandaboard (ARM arch) would be very interesting.

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          • #6
            I'm also looking forward to see some Zcache benchmarks. Especially as there is now support for the snappy compressor.

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            • #7
              Originally posted by liam View Post
              I wonder if Android has adopted this?
              If not, hopefully CM has/will do so. This would help tremendously with devices with <=512MB.
              However, if the damn SoC would start putting sata connectors on these devices so we could use storage that gets decent I/O we wouldn't need it.
              These current storage devices are slow as hell. Sure, they're cheap, but why hasn't, say, Apple (who is supposed to be premium) done something about this situation? Can you imagine how much it would lower game load times?
              Sure, you could use that high bandwidth SD card standard (is it SD or the other one?) but that seems to only be available on some phones, and I'm not sure how fast that is b/c SD cards typically suck as well.
              Supposedly, part of the reason is that manufacturors use cheap, 3 bits/cell flash. Certainly moving to at least 2bit/cell (though SLC makes more sense to me considering the size of these drives and how much writing they endure) would be worth the tradeoff in size/price for the performance gain?
              Yes Zcache is in Cyanogenmod under the performance settings - although it still might be listed under it's old name as they're using the 2.6.38 kernel

              Comment


              • #8
                Originally posted by Chewi View Post
                I'm currently finding myself more pressed for RAM than CPU. I hadn't heard of zcache before so I might try it out.
                I tried it once but it's a bit of a bugger setting up

                Comment


                • #9
                  Originally posted by spirtbrat View Post
                  I'm also looking forward to see some Zcache benchmarks. Especially as there is now support for the snappy compressor.
                  Do you think that there will be Zcache benchmarks? Thats interesting. I know that IBM never releases Mainframe benchmarks, because IBM does not want people to know how slow the cpus actually are. For instance, you will never find any SPEC_INT benchmarks for Mainframes. Then you could compare a normal x86 cpu, vs a Mainframe, and you will see that the Mainframe is way slower.

                  Comment


                  • #10
                    Originally posted by FireBurn View Post
                    I tried it once but it's a bit of a bugger setting up
                    Why do you say that? I tried it last night. Enabled the relevant kernel options, compiled, installed, rebooted... realised I needed to put "zcache" on the kernel command line... rebooted again and there it was. It doesn't seem to have done anything yet (/sys/kernel/mm/zcache/zbud_cumul_zbytes reports 0) but I haven't really pushed it yet.

                    Comment


                    • #11
                      Originally posted by kebabbert View Post
                      Do you think that there will be Zcache benchmarks? Thats interesting. I know that IBM never releases Mainframe benchmarks, because IBM does not want people to know how slow the cpus actually are. For instance, you will never find any SPEC_INT benchmarks for Mainframes. Then you could compare a normal x86 cpu, vs a Mainframe, and you will see that the Mainframe is way slower.
                      This is unrelated to IBM. Also I think some are confusing zcache with zram, IIRC only zram is available in the CM rom. Zram on its own is very useful on low-ram systems though, I should know.

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                      • #12
                        Originally posted by curaga View Post
                        This is unrelated to IBM. Also I think some are confusing zcache with zram, IIRC only zram is available in the CM rom. Zram on its own is very useful on low-ram systems though, I should know.
                        Isn't zram that new memory tech?
                        Zcache, I thought, was a user of transcendental memory with the addition of compression.

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                        • #13
                          Badly chosen name just like DRM

                          zram in the kernel == lzo-compressed ram disk, usually used for swap. zcache as I understand it enables the compression of caches like the various filesystem caches. That it's on top of transcendental memory is just coincidence, the first versions weren't (IIRC).

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                          • #14
                            I'm pleased with the results. I've been using this machine to run a Minecraft server while playing on it at the same time. Since using Bukkit (server mod), the RAM usage has been a bit heavier and it's started hitting swap, resulting in nasty slow downs. I tried it just now with zcache enabled and it didn't hit swap once.

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                            • #15
                              Originally posted by curaga View Post
                              Badly chosen name just like DRM

                              zram in the kernel == lzo-compressed ram disk, usually used for swap. zcache as I understand it enables the compression of caches like the various filesystem caches. That it's on top of transcendental memory is just coincidence, the first versions weren't (IIRC).
                              Yeah, so they can do similar things but zram doesn't need the transcendental memory aspect (which is, IMHO, one of its --zcache-- big selling points).
                              I was thinking of this (http://lwn.net/Articles/397574/) and zram was mentioned in the comments (http://lwn.net/Articles/397894/).

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