[lkml]   [1998]   [Dec]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    Patch in this message
    SubjectRe: [PATCH] i386 entry.S alignment tweak
    On Sat, Dec 12, 1998 at 01:40:33PM -0800, Linus Torvalds wrote:
    > On Fri, 11 Dec 1998, MOLNAR Ingo wrote:
    > > either we align system_call, or we align ret_from_sys_call, we cant have
    > > both. Given that ret_from_sys_call is shared with IRQ handlers, it's
    > > better performance-wise to align that one.
    > Don't bother about IRQ handlers. Either they take a cache miss or they
    > don't, it's not something we should worry about: if the interrupts happen
    > so much that it matters then the system is not very usable anyway for
    > completely other reasons than one cache miss.
    > It's only system calls we really want to have minimal cache footprints and
    > good behaviour - ie the entrypoint should be aligned, and the mid-way
    > point should _not_ have extra nop's to align it. System calls are
    > critical, and can often be entered with cold caches.

    So you want this patch then?

    BTW, they're not nop instructions these days: they're the largest
    filler instructions gas can put in, so an alignment of a few bytes
    needn't take any longer to execute than a single byte alignment.

    -- Jamie

    --- linux/arch/i386/kernel/entry.S.devel Sun Dec 6 15:44:17 1998
    +++ linux/arch/i386/kernel/entry.S Mon Dec 14 01:07:29 1998
    @@ -176,7 +176,6 @@
    jne tracesys
    call *SYMBOL_NAME(sys_call_table)(,%eax,4)
    movl %eax,EAX(%esp) # save the return value
    - ALIGN
    .globl ret_from_sys_call
    .globl ret_from_intr

    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    Please read the FAQ at

     \ /
      Last update: 2005-03-22 13:46    [W:0.020 / U:29.272 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site