On Thu, 5 Jul 2007 12:13:09 -0600 Mike Stroyan <[EMAIL PROTECTED]> wrote: > The L3 cache is involved in the HP-UX defect description because the > earlier HP-UX patch PHKL_33781 added flushing of the instruction cache > when an executable mapping was removed. Linux never added that > unsuccessfull attempt at montecito cache coherency. In the current > linux situation it can execute old cache lines straight from L2 icache. > Hmm... I couldn't understand "why icache includes old lines in a new page." This happens at - a file is newly loaded into page-cache. - only on NFS. - happens very *often* if the program is unlucky.
So I wrote my understainding as I think. > > Now, I think icache should be flushed before set_pte(). > > This is a patch to try that. > > > > 1. remove all lazy_mmu_prot_update()...which is used by only ia64. > > 2. implements flush_cache_page()/flush_icache_page() for ia64. > > > > Something unsure.... > > 3. mprotect() flushes cache before removing pte. Is this sane ? > > I added flush_icache_range() before set_pte() here. > > > > Any comments and advices ? > > I am concerned about performance consequences. With the change > from lazy_mmu_prot_update to __flush_icache_page_ia64 you dropped > the code that avoids icache flushes for non-executable pages. Hmm? I added VM_EXEC check in flush_(d|i)cache_page(). Isn't it enough ? > Section 4.6.2 of David Mosberger and Stephane Eranian's > "ia-64 linux kernel design and implementation" goes into some > detail about the performance penalties avoided by limiting icache > flushes to executable pages and defering flushes until the first > fault for execution. > > Have you done any benchmarking to measure the performance > effect of these additional cache flushes? It would be particularly > interesting to measure on large systems with many CPUs. The fc.i > instruction needs to be broadcast to all CPUs in the system. no benchmarks yet. > > The only defect that I see in the current implementation of > lazy_mmu_prot_update() is that it is called too late in some > functions that are already calling it. Are your large changes > attempting to correct other defects? Or are you simplifying > away potentially valuable code because you don't understand it? > I know your *simple* patch in April wasn't included. So I wrote this. In April thread, commenter's advices was "implement flush_icache_page()" I think. If you have a better patch, please post. Thanks, -Kame - 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/
