On Sat, 24 Mar 2007 00:11:32 -0700 "Ken Chen" <[EMAIL PROTECTED]> wrote:
> On 3/23/07, Andrew Morton <[EMAIL PROTECTED]> wrote: > > a) Ken observes that obtaining private hugetlb memory via hugetlbfs > > involves "fuss". > > > > b) the libhugetlbfs maintainers then go off and implement a no-fuss way of > > doing this. > > Hmm, what started this thread was libhugetlbfs maintainer complained > how "fuss" it was to create private hugetlb mapping and suggested an > even bigger kernel change with pagetable_operations API. OK. I wasn't paying particularly close attention. But my rant still stands ;) > The new API > was designed with an end goal of introduce /dev/hugetlb (as one of the > feature, they might be thinking more). What motivated me here is to > point out that we can achieve the same goal of having a /dev/hugetlb > with existing hugetlbfs infrastructure and the implementation is > relatively straightforward. What it also buys us is a bit more > flexibility to the end user who wants to use the interface directly. OK. Why is it a "fuss" to do this with hugetlbfs files, btw? Having read back through the thread, the only substantiation I can really see is The pagetable_operations API opens up possibilities to do some additional (and completely sane) things. For example, I have a patch that alters the character device code below to make use of a hugetlb ZERO_PAGE. This eliminates almost all the up-front fault time, allowing pages to be COW'ed only when first written to. We cannot do things like this with hugetlbfs anymore because we have a set of complex semantics to preserve. Why is this actually a useful feature? What does "complex semantics to preserve" mean? I dunno. I see a lot of code flying around, but comparatively little effort to describe the actual problems which we're trying to solve. - 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/
