On Monday 20 June 2005 20:51, Jeff Dike wrote:
> There is absolutely no reason to flush the kernel's VM area during a
> tlb_flush_mm.
>
> This results in a noticable performance increase in the kernel build
> benchmark.
Andrew: hold off this one, definitely.
Jeff: Have you verified this with both modules enabled and iptables (a vmalloc
user) compiled modularly? Maybe even non-modular iptables will trigger the
bug but let's go for sure.
This situation killed a conceptually similar patch in 2.4.24-2um (which did
apply until 2.6.11):
diff -puN arch/um/kernel/skas/tlb.c~optimization-unstable
arch/um/kernel/skas/tlb.c
--- UmWorklinux-2.4.24/arch/um/kernel/skas/tlb.c~optimization-unstable
2004-07-02 13:45:07.057643968 +0200
+++ UmWorklinux-2.4.24-paolo/arch/um/kernel/skas/tlb.c 2004-07-02
13:45:14.098573584 +0200
@@ -132,7 +132,9 @@ void flush_tlb_range_skas(struct mm_stru
void flush_tlb_mm_skas(struct mm_struct *mm)
{
+#if 0
flush_tlb_kernel_vm_skas();
+#endif
fix_range(mm, 0, host_task_size, 0);
}
Given that:
void flush_tlb_kernel_vm_skas(void)
{
flush_tlb_kernel_range_skas(start_vm, end_vm);
}
and flush_tlb_kernel_range_skas was renamed to _common, I argue that this
patch is exactly the same one and will have the same bad effect.
> Signed-off-by: Jeff Dike <[email protected]>
>
> Index: linux-2.6.12/arch/um/kernel/skas/tlb.c
> ===================================================================
> --- linux-2.6.12.orig/arch/um/kernel/skas/tlb.c 2005-06-20
> 11:54:56.000000000 -0400 +++
> linux-2.6.12/arch/um/kernel/skas/tlb.c 2005-06-20 12:11:00.000000000 -0400
> @@ -76,7 +76,6 @@ void flush_tlb_mm_skas(struct mm_struct
> return;
>
> fix_range(mm, 0, host_task_size, 0);
> - flush_tlb_kernel_range_common(start_vm, end_vm);
> }
>
> void force_flush_all_skas(void)
--
Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!".
Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894)
http://www.user-mode-linux.org/~blaisorblade
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