On Wed, Oct 7, 2015 at 11:08 AM, Denys Vlasenko <[email protected]> wrote: > On 10/06/2015 02:48 AM, Andy Lutomirski wrote: >> + >> +/* Opportunistic SYSEXIT */ >> + TRACE_IRQS_ON /* User mode traces as IRQs on. */ >> + movl PT_EIP(%esp), %edx /* pt_regs->ip */ >> + movl PT_OLDESP(%esp), %ecx /* pt_regs->sp */ >> + popl %ebx /* pt_regs->bx */ >> + addl $2*4, %esp /* skip pt_regs->cx and pt_regs->dx */ > > Here stack engine and ALUs operating on ESP conflict, > potentially adding a stall both before and after ADD. > > It might be faster to just pop twice into an unused register, say, > popl %eax > popl %eax > >> + popl %esi /* pt_regs->si */ >> + popl %edi /* pt_regs->di */ >> + popl %ebp /* pt_regs->bp */ >> + popl %eax /* pt_regs->ax */ >> 1: mov PT_FS(%esp), %fs >> PTGS_TO_GS >
I'll benchmark it and possibly add it at the end of the series. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
