From: Roland Dreier <rdreier-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>
To: Jason Gunthorpe
<jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
Cc: Jeff Squyres <jsquyres-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>,
Linux RDMA List
<linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Brad Benton <brad.benton-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
Subject: Re: Ummunotify: progress at last!
Date: Tue, 23 Mar 2010 23:17:26 -0700 [thread overview]
Message-ID: <adavdcm1bwp.fsf@roland-alpha.cisco.com> (raw)
In-Reply-To: <20100324055913.GA9769-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> (Jason Gunthorpe's message of "Tue, 23 Mar 2010 23:59:13 -0600")
> > I wonder, is that a win? I guess you don't even have to pin it, just do
> > copy_to_user() to update the counter, but mmap doesn't seem so bad.
>
> Not sure you can call copy_to_user from a mmu_notifier callback? What
> if it faults?
Good point... we could defer it to a context where we could block but...
> I think the idea would be that by letting user space select the
> counter location it could place it in a sensible cachline/etc and
> probably avoid a pointer indirection.
OK, I have to look at the perf stuff. That makes sense but OTOH
userspace could (unknowingly) pick a highmen page and then we end up
having to do kmap_atomic or something from an mmu notifier callback.
--
Roland Dreier <rolandd-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>
For corporate legal information go to:
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prev parent reply other threads:[~2010-03-24 6:17 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-23 16:06 Ummunotify: progress at last! Jeff Squyres
[not found] ` <1CDB2AA4-A8DF-4169-943E-4EA190814596-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>
2010-03-23 16:59 ` Jason Gunthorpe
[not found] ` <20100323165920.GH29129-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2010-03-23 17:17 ` Jeff Squyres
[not found] ` <D7DCABC9-4BB2-4FBA-A7B3-C06F4A848467-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>
2010-03-23 17:29 ` Jason Gunthorpe
[not found] ` <20100323172953.GI29129-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2010-03-23 19:17 ` Jeff Squyres
[not found] ` <5F80899D-F989-4162-B050-7E4D6B389876-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>
2010-03-23 19:52 ` Jason Gunthorpe
[not found] ` <20100323195251.GJ29129-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2010-03-23 20:01 ` Jeff Squyres
[not found] ` <3B848E1F-C9B6-416A-9E6E-99604E71902A-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>
2010-03-23 20:11 ` Jason Gunthorpe
[not found] ` <20100323201124.GK29129-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2010-03-24 5:59 ` Roland Dreier
[not found] ` <adaljdi2rap.fsf-BjVyx320WGW9gfZ95n9DRSW4+XlvGpQz@public.gmane.org>
2010-03-24 17:43 ` Jason Gunthorpe
2010-04-07 19:37 ` Roland Dreier
[not found] ` <ada39z72gww.fsf-BjVyx320WGW9gfZ95n9DRSW4+XlvGpQz@public.gmane.org>
2010-04-07 20:05 ` Jason Gunthorpe
2010-03-24 5:53 ` Roland Dreier
2010-03-24 5:55 ` Roland Dreier
[not found] ` <adapr2u2rib.fsf-BjVyx320WGW9gfZ95n9DRSW4+XlvGpQz@public.gmane.org>
2010-03-24 5:59 ` Jason Gunthorpe
[not found] ` <20100324055913.GA9769-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2010-03-24 6:17 ` Roland Dreier [this message]
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