Messages in this thread | | | From | KOSAKI Motohiro <> | Subject | Re: [RFC] mlock: release mmap_sem every 256 faulted pages | Date | Tue, 23 Nov 2010 16:49:49 +0900 (JST) |
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> On Mon, 22 Nov 2010 21:00:52 -0800 Michel Lespinasse <walken@google.com> wrote: > > > Hi, > > > > I'd like to sollicit comments on this proposal: > > > > Currently mlock() holds mmap_sem in exclusive mode while the pages get > > faulted in. In the case of a large mlock, this can potentially take a > > very long time. > > A more compelling description of why this problem needs addressing > would help things along.
Michel, as far as I know, now Michael Rubin (now I'm ccing him) are trying to make automatic MM test suit. So if possible, can you please make test case which reproduce your workload?
http://code.google.com/p/samplergrapher/
I hope to join to solve your issue. and I also hope you help to understand and reproduce your issue.
Thanks.
> > > + /* > > + * Limit batch size to 256 pages in order to reduce > > + * mmap_sem hold time. > > + */ > > + nfault = nstart + 256 * PAGE_SIZE; > > It would be nicer if there was an rwsem API to ask if anyone is > currently blocked in down_read() or down_write(). That wouldn't be too > hard to do. It wouldn't detect people polling down_read_trylock() or > down_write_trylock() though.
Andrew, yes it is certinally optimal. But I doubt it improve mlock performance a lot. because mlock is _very_ slooooooow syscall. lock regrabing may be cheap than it. So, _IF_ you can allow, I hope we take a simple method at first. personally I think Michel move forwarding right way. then I don't hope to make a hardest hurdle.
Thanks.
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