Re: C3600 kernel/64bit 4.* slow IO due to -mlong-calls

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Hi Carlo,

On 15.03.2018 16:36, Carlo Pisani wrote:
> I am experiencing a very annoying behavior with my HPPA C3600: if I
> compile the (linux) kernel with  -mlong-calls then the IO (e.g. file
> copy) becomes very slow, and the PCI becomes unstable (i.e. it crashes
> the machine)
> 
> kernel  gcc     binutils    with mlong    without mlong
> 4.15.7  4.9.3   2.25.1     13.4 MB/s    27.0 MB/s
> 4.15.7  6.4.0   2.25.1     13.4 MB/s    27.0 MB/s
> 4.15.7  6.4.0   2.29.1     14.4 MB/s    25.0 MB/s

Interesting bad results!
 
> these tests were performed with
> 
> dd if=/dev/zero of=here bs=1k count=100000
> 
> -mlong-calls is enabled in the kernel by "CONFIG_MLONGCALLS"

I think nobody else noticed the bad performance due to CONFIG_MLONGCALLS yet.
I've now started some testing if we can disable that option on the debian
kernels...

> the help-guide says "If you configure the kernel to include many
> drivers built-in instead as modules, the kernel executable may become
> too big, so that the linker will not be able to resolve some long
> branches and fails to link your vmlinux kernel. In that case enabling
> this option will help you to overcome this limit by using the
> -mlong-calls compiler option. Usually you want to say N here, unless
> you e.g. want to build a kernel which includes all necessary drivers
> built-in and which can be used for TFTP booting without the need to
> have an initrd ramdisk. Enabling this option will probably slow down
> your kernel"
> 
> I need -mlong-calls because I need to compile the kernel without
> kernel-modules

Why?

> all built-in, that makes the size of the kernel of
> about 23Mbytes, thus without -mlong-calls the linker fails to "link"
> objects
> 
> let me know

I'm not sure what kind of help you expect here?
The only option I see is that you try to disable some options (modules) you won't
need and thus reduce the kernel size. xfs, ipv6 and such are good candidates.
Or use a 32bit kernel ?

Helge
--
To unsubscribe from this list: send the line "unsubscribe linux-parisc" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html



[Index of Archives]     [Linux SoC]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux