From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-x230.google.com (mail-pf0-x230.google.com [IPv6:2607:f8b0:400e:c00::230]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3qvhVC4BJ0zDq60 for ; Wed, 27 Apr 2016 11:01:07 +1000 (AEST) Received: by mail-pf0-x230.google.com with SMTP id y69so13508799pfb.1 for ; Tue, 26 Apr 2016 18:01:07 -0700 (PDT) Subject: Re: [PATCH] powerpc/mm: Use jump label to speed up radix_enabled check To: Benjamin Herrenschmidt , "Aneesh Kumar K.V" , paulus@samba.org, mpe@ellerman.id.au References: <1461687855-23017-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1461704701.3135.68.camel@kernel.crashing.org> <571FE8C1.4030903@gmail.com> <1461711943.3135.72.camel@kernel.crashing.org> Cc: linuxppc-dev@lists.ozlabs.org From: Balbir Singh Message-ID: <57200F4A.4070104@gmail.com> Date: Wed, 27 Apr 2016 11:00:58 +1000 MIME-Version: 1.0 In-Reply-To: <1461711943.3135.72.camel@kernel.crashing.org> Content-Type: text/plain; charset=utf-8 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 27/04/16 09:05, Benjamin Herrenschmidt wrote: > On Wed, 2016-04-27 at 08:16 +1000, Balbir Singh wrote: >> >> On 27/04/16 07:05, Benjamin Herrenschmidt wrote: >>> >>> On Tue, 2016-04-26 at 21:54 +0530, Aneesh Kumar K.V wrote: >>>> >>>> This add generic mmu_feature_enabled() function that get patched >>>> to take right code path based on the feature bit enabled. The >>>> main >>>> difference between the existing mmu_has_feature() function is the >>>> hot patching using jump label framework. >>>> >>>> The implementation wraps around mmu_has_feature so that we can >>>> use >>>> this in early bootup code before we do the hotpatching. >>> I'd rather we make mmu_has_feature() use jump labels and is the >>> "main" >>> API to be used by most code. If we have a need for a lower-level >>> version for use by early boot code, call it __mmu_has_feature(). >>> >>> This is more in-line with existing kernel practices and avoids >>> having >>> two APIs that somewhat look the same where it's not clear which one >>> should be used. >>> >> Makes sense, but I suspect its a larger impact with loads of testing >> required across platforms. Should this be done incrementally? > > What kind of impact do you expect ? > Just basic testing across CPUs with various mm features enabled/disabled. Just for sanity Balbir