On Fri, Oct 30, 2015 at 04:02:04PM +0100, Michael Holzheu wrote: > The slurp_fd() function allocates memory and uses the read() system call. > This results in double memory consumption for image and initrd: > > 1) Memory allocated in user space by the kexec tool > 2) Memory allocated in kernel by the kexec() system call > > The following illustrates the use case that we have on s390x: > > 1) Boot a 4 GB Linux system > 2) Copy kernel and 1,5 GB ramdisk from external source into tmpfs (ram) > 3) Use kexec to boot kernel with ramdisk > > Therefore for kexec runtime we need: > > 1,5 GB (tmpfs) + 1,5 GB (kexec malloc) + 1,5 GB (kernel memory) = 4,5 GB > > This patch introduces slurp_file_mmap() which for "normal" files uses > mmap() instead of malloc()/read(). This reduces the runtime memory > consumption of the kexec tool as follows: > > 1,5 GB (tmpfs) + 1,5 GB (kernel memory) = 3 GB > > Signed-off-by: Michael Holzheu <holzheu at linux.vnet.ibm.com> > Reviewed-by: Dave Young <dyoung at redhat.com> Thanks, applied.
