Messages in this thread | | | Date | Tue, 10 Oct 2006 02:25:17 +1000 | From | Nick Piggin <> | Subject | Re: [PATCH] Try to avoid a pessimistic vmalloc() recursion |
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Eric Dumazet wrote: > __vmalloc_area_node() is a litle bit pessimist when allocating space for > storing struct page pointers. > > When allocating more than 4 MB on ia32, or 2 MB on x86_64, > __vmalloc_area_node() has to allocate more than PAGE_SIZE bytes to store > pointers to page structs. This means that two TLB translations are needed to > access data. > > This patch tries a kmalloc() call, then only if this first attempt failed, a > vmalloc() is performed. (Later, at vfree() time we chose kfree() or vfree() > with a test on flags & VM_VPAGES : no change is needed) > > Most of the time, the first kmalloc() should be OK, so we reduce TLB usage.
But this is only TLB usage when managing (read: freeing) the vmalloc pages, isn't it? Not when actually accessing the data.
I'd be inclined to NACK this, unless you can show an improvement somewhere: it is suboptimal to even _try_ allocating higher order pages.
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