Sorry, forgot to add linux-arm-kernel at lists.infradead.org. Now CCed. On 07/12/2015:05:15:47 PM, Pratyush Anand wrote: > +linux-arm-kernel at lists.infradead.org (May be someone from arm kernel list can > give some more input) > > On 04/11/2015:11:56:51 PM, Scott Wood wrote: > > On Thu, 2015-10-22 at 12:08 -0700, Geoff Levand wrote: > > > I notice the difference on the my arm64 system, so I guess we > > > are even on that. > > > > For me it was beyond "notice the difference" -- I thought it was completely > > broken, and was preparing to debug, until it started spitting out output over > > a minute later. > > > > Compiling the sha256 code with -O2 instead of -O0 cut it down to around 10 > > seconds (still unpleasant, but not quite as crazy... still unacceptable for > > non-kdump, though). > > Yes, compiling purgatory code with -O2 helps to improve the timing, and I notice > that enabling D-cache on top of -O2 does not improve it further. However, I am > still not able to understand that why there is huge difference between following > two. > > 1) When we execute kexec() system call in first kernel, at that time it > calculates sha256 on all the binaries [1]. It take almost un-noticeable time > (less than a sec) there. > > 2) When purgatory is executed then it re-calculates sha256 using same routines > [2] on same binary data as that of case (1). But, now it takes 10-20 sec > (depending of size of binaries)? > > Why did not it take same time with O2 + D-cache enabled? I think, we should be > able to achieve same time in second case as well. What is missing? > > ~Pratyush > > [1] http://git.kernel.org/cgit/utils/kernel/kexec/kexec-tools.git/tree/kexec/kexec.c#n650 > [2] http://git.kernel.org/cgit/utils/kernel/kexec/kexec-tools.git/tree/purgatory/purgatory.c#n20
