From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vladislav Bolkhovitin Subject: Re: About a shortcoming of the verbs API Date: Mon, 09 Aug 2010 22:45:08 +0400 Message-ID: <4C604CB4.5060705@vlnb.net> References: <20100727182046.GT7920@obsidianresearch.com> <1281365347.4968.5.camel@lap75545.ornl.gov> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1281365347.4968.5.camel-FqX9LgGZnHWDB2HL1qBt2PIbXMQ5te18@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: David Dillow Cc: Bart Van Assche , Roland Dreier , Jason Gunthorpe , Linux-RDMA List-Id: linux-rdma@vger.kernel.org David Dillow, on 08/09/2010 06:49 PM wrote: > On Sun, 2010-08-08 at 20:19 +0200, Bart Van Assche wrote: >> On Sat, Aug 7, 2010 at 6:32 PM, Roland Dreier wrote: >>> Not sure that I follow the problem you're worried about. A given >>> tasklet can only be running on one CPU at any one time -- if an >>> interrupt occurs and reschedules the tasklet then it just runs again >>> when it exits. >>> >>> Also I'm not sure I understand why this is special for IB hardware -- >>> standard practice is for interrupt handlers to clear the interrupt >>> source and reenable interrupts, so I don't see why the same thing you >>> describe can't happen with any interrupt-generating device that defers >>> work to a tasklet. >> >> One of the applications I have been looking at is adding blk-iopoll >> support in ib_srp and to make it possible to enable and disable >> blk-iopoll at runtime via sysfs. A naive implementation could look >> e.g. as follows: > > I'm not sure it makes sense to enable/disable this at runtime -- we > don't do it for NAPI, why do it for block devices? I'm not even sure I'd > want to see a config option for it in kbuild -- that was done during the > transition to NAPI and it lingered forever for some drivers. I'd rather > we got it correct, and not give people yet another knob to figure out. > > I can certainly see a use case for testing the patch's performance, > though. For the testing it can be done as a local to the corresponding file #ifdef. Vlad -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html