On Mon, 17 Jan 2000, Manfred Spraul wrote:
> From: "Ingo Molnar" <mingo@chiara.csoma.elte.hu>
> > __flush_tlb() is noticeably faster than __flush_tlb_global().
> > The two affected places, zap_low_mappings() and flush_all_zero_pkmaps()
> > are now using the new flush_tlb_all_kernel() call.
>
> I guess flush_all_zero_pkmaps() will happen quite often, it might be the
> most common caller of flush_tlb_all() [other reasons are module load/unload,
> or creating a process that uses more than 1024 file handles - extremely rare
> events] . I would remove the PAGE_GLOBAL bit from the kmap pages, then we do
> not need another flush_tlb function that's referenced from the
> cross-platform part of the kernel.
no, it does not happen often at all, even under heavy load the ratio
between cached kmaps and full flushes is 1:10000. So the advantage of
using _PG_GLOBAL in kmaps is pretty significant i believe, especially
since the pagecache is in high memory.
i believe mapping/unmapping memory in threaded apps generates the most TLB
flushes.
-- mingo
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