From mboxrd@z Thu Jan 1 00:00:00 1970 From: rostedt@goodmis.org (Steven Rostedt) Date: Tue, 17 Mar 2015 08:13:41 -0400 Subject: [RFC][PATCH] ring-buffer: Replace this_cpu_{read,write} with this_cpu_ptr() In-Reply-To: References: <20150316173154.537b80ee@gandalf.local.home> Message-ID: <20150317081341.0f9a8b4c@gandalf.local.home> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, 17 Mar 2015 00:56:51 -0500 (CDT) Christoph Lameter wrote: > On Mon, 16 Mar 2015, Steven Rostedt wrote: > > > It has come to my attention that this_cpu_read/write are horrible on > > architectures other than x86. Worse yet, they actually disable > > preemption or interrupts! This caused some unexpected tracing results > > on ARM. > > Well its just been 7 years or so. Took a long time it seems. The code that I added was not 7 years old. And not all people send me reports like this. > > These would need to be implemented on the architectures to > have comparable performance. > > > I may go and remove all this_cpu_read,write() calls from my code > > because of this. > > You could do that with __this_cpo_* but not this_cpu_*(). Doing > it to this_cpu_* would make the operations no longer per cpu atomic. If > they do not need per cpu atomicity then you could have used __this_cpu_* > instead. And __this_cpu_* do not disable preemption or interrupts. I do not need it to be atomic. > > So please do not send patches based on gut reactions. What else would you like me to do? It was an RFC, and it worked. > > NAK For this particular patch, I may override the NAK as I do not see a downside for it. Why should x86 get an advantage at the expense of ARM? -- Steve