Hi Pratyush, On 07/12/15 11:48, Pratyush Anand wrote: >> 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? I haven't benchmarked this, but: util_lib/sha256.c contains calls out to memcpy(). In your case 1, this will use the glibc version. In case 2, it will use the version implemented in purgatory/string.c, which is a byte-by-byte copy. Thanks, James
