Hi! > >> I've measured the kernel decompression speed using QEMU before and after > >> this patch for the x86_64 and i386 architectures. The speed-up is about > >> 10x as shown below. > >> > >> Code Arch Kernel Size Time Speed > >> v5.8 x86_64 11504832 B 148 ms 79 MB/s > >> patch x86_64 11503872 B 13 ms 885 MB/s > >> v5.8 i386 9621216 B 91 ms 106 MB/s > >> patch i386 9620224 B 10 ms 962 MB/s > >> > >> I also measured the time to decompress the initramfs on x86_64, i386, > >> and arm. All three show the same decompression speed before and after, > >> as expected. > >> > >> [1] https://github.com/lz4/lz4/pull/890 > >> > > > > Hi Nick, would you be able to test the below patch's performance to > > verify it gives the same speedup? It removes the #undef in misc.c which > > causes the decompressors to not use the builtin version. It should be > > equivalent to yours except for applying it to all the decompressors. > > > > Thanks. > > I will measure it. I would expect it to provide the same speed up. It would > be great to fix > the problem for x86/i386 in general. > > But, I believe that this is also a problem for ARM, though I have a hard time > measuring > because I can’t get pre-boot print statements in QEMU. I will attempt to take > a look at the > assembly, because I’m fairly certain that memcpy() isn’t inlined in master. > > Even if we fix all the architectures, I would still like to merge the LZ4 > patch. It seems like it > is pretty easy to merge a patch that is a boot speed regression, because > people aren’t > actively measuring it. So I prefer a layered defense.
Layered defense against performance-only problem, happening on
emulation-only?
IMO that's a bit of overkill.
Best regards,
Pavel
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