From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx144.postini.com [74.125.245.144]) by kanga.kvack.org (Postfix) with SMTP id E4AE46B006C for ; Fri, 15 Jun 2012 12:50:36 -0400 (EDT) Received: from /spool/local by e8.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 15 Jun 2012 12:50:34 -0400 Received: from d01relay04.pok.ibm.com (d01relay04.pok.ibm.com [9.56.227.236]) by d01dlp01.pok.ibm.com (Postfix) with ESMTP id 3850838C805C for ; Fri, 15 Jun 2012 12:49:38 -0400 (EDT) Received: from d03av05.boulder.ibm.com (d03av05.boulder.ibm.com [9.17.195.85]) by d01relay04.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q5FGnaJn187048 for ; Fri, 15 Jun 2012 12:49:37 -0400 Received: from d03av05.boulder.ibm.com (loopback [127.0.0.1]) by d03av05.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q5FGnYpp032326 for ; Fri, 15 Jun 2012 10:49:35 -0600 Message-ID: <4FDB674C.9070304@linux.vnet.ibm.com> Date: Fri, 15 Jun 2012 11:48:12 -0500 From: Seth Jennings MIME-Version: 1.0 Subject: Re: [PATCH v2 3/3] x86: Support local_flush_tlb_kernel_range References: <1337133919-4182-1-git-send-email-minchan@kernel.org> <1337133919-4182-3-git-send-email-minchan@kernel.org> <4FB4B29C.4010908@kernel.org> <1337266310.4281.30.camel@twins> <4FDB5107.3000308@linux.vnet.ibm.com> <7e925563-082b-468f-a7d8-829e819eeac0@default> In-Reply-To: <7e925563-082b-468f-a7d8-829e819eeac0@default> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Dan Magenheimer Cc: Peter Zijlstra , Minchan Kim , Greg Kroah-Hartman , Nitin Gupta , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Thomas Gleixner , Ingo Molnar , Tejun Heo , David Howells , x86@kernel.org, Nick Piggin , Konrad Rzeszutek Wilk On 06/15/2012 11:35 AM, Dan Magenheimer wrote: >> From: Seth Jennings [mailto:sjenning@linux.vnet.ibm.com] >> Sent: Friday, June 15, 2012 9:13 AM >> To: Peter Zijlstra >> Cc: Minchan Kim; Greg Kroah-Hartman; Nitin Gupta; Dan Magenheimer; linux-kernel@vger.kernel.org; >> linux-mm@kvack.org; Thomas Gleixner; Ingo Molnar; Tejun Heo; David Howells; x86@kernel.org; Nick >> Piggin >> Subject: Re: [PATCH v2 3/3] x86: Support local_flush_tlb_kernel_range >> >> On 05/17/2012 09:51 AM, Peter Zijlstra wrote: >> >>> On Thu, 2012-05-17 at 17:11 +0900, Minchan Kim wrote: >>>>> +++ b/arch/x86/include/asm/tlbflush.h >>>>> @@ -172,4 +172,16 @@ static inline void flush_tlb_kernel_range(unsigned long start, >>>>> flush_tlb_all(); >>>>> } >>>>> >>>>> +static inline void local_flush_tlb_kernel_range(unsigned long start, >>>>> + unsigned long end) >>>>> +{ >>>>> + if (cpu_has_invlpg) { >>>>> + while (start < end) { >>>>> + __flush_tlb_single(start); >>>>> + start += PAGE_SIZE; >>>>> + } >>>>> + } else >>>>> + local_flush_tlb(); >>>>> +} >>> >>> It would be much better if you wait for Alex Shi's patch to mature. >>> doing the invlpg thing for ranges is not an unconditional win. >> >> From what I can tell Alex's patches have stalled. The last post was v6 >> on 5/17 and there wasn't a single reply to them afaict. >> >> According to Alex's investigation of this "tipping point", it seems that >> a good generic value is 8. In other words, on most x86 hardware, it is >> cheaper to flush up to 8 tlb entries one by one rather than doing a >> complete flush. >> >> So we can do something like: >> >> if (cpu_has_invlpg && (end - start)/PAGE_SIZE <= 8) { >> while (start < end) { >> >> Would this be acceptable? > > Hey Seth, Nitin -- > > After more work digging around zsmalloc and zbud, I really think > this TLB flushing, as well as the "page pair mapping" code can be > completely eliminated IFF zsmalloc is limited to items PAGE_SIZE or > less. To add to what Nitin just sent, without the page mapping, zsmalloc and the late xvmalloc have the same issue. Say you have a whole class of objects that are 3/4 of a page. Without the mapping, you can't cross non-contiguous page boundaries and you'll have 25% fragmentation in the memory pool. This is the whole point of zsmalloc. -- Seth -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org