| Subject | Re: [PATCH 06/13] mm: Preemptible mmu_gather | From | Peter Zijlstra <> | Date | Fri, 09 Apr 2010 10:18:43 +0200 |
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On Fri, 2010-04-09 at 13:25 +1000, Nick Piggin wrote: > On Thu, Apr 08, 2010 at 09:17:43PM +0200, Peter Zijlstra wrote: > > @@ -39,30 +33,48 @@ > > struct mmu_gather { > > struct mm_struct *mm; > > unsigned int nr; /* set to ~0U means fast mode */ > > + unsigned int max; /* nr < max */ > > unsigned int need_flush;/* Really unmapped some ptes? */ > > unsigned int fullmm; /* non-zero means full mm flush */ > > - struct page * pages[FREE_PTE_NR]; > > +#ifdef HAVE_ARCH_MMU_GATHER > > + struct arch_mmu_gather arch; > > +#endif > > + struct page **pages; > > + struct page *local[8]; > > Have you done some profiling on this? What I would like to see, if > it's not too much complexity, is to have a small set of pages to > handle common size frees, and then use them up first by default > before attempting to allocate more. > > Also, it would be cool to be able to chain allocations to avoid > TLB flushes even on big frees (overridable by arch of course, in > case they're doing some non-preeemptible work or you wish to break > up lock hold times). But that might be just getting over engineered.
Did no profiling at all, back when I wrote this I was in a hurry to get this working for -rt.
But yes, those things do look like something we want to look into, we can easily add a head structure to these pages like we did for the RCU batches.
But as it stands I think we can do those things as incrementals on top of this, no?
What kind of workload would you recommend I use to profile this?
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