From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from aserp1040.oracle.com (aserp1040.oracle.com [141.146.126.69]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3xP7dc0cRKzDq7Z for ; Fri, 4 Aug 2017 23:52:02 +1000 (AEST) Subject: Re: [v5 09/15] sparc64: optimized struct page zeroing To: Sam Ravnborg Cc: linux-kernel@vger.kernel.org, sparclinux@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-arm-kernel@lists.infradead.org, x86@kernel.org, kasan-dev@googlegroups.com, borntraeger@de.ibm.com, heiko.carstens@de.ibm.com, davem@davemloft.net, willy@infradead.org, mhocko@kernel.org References: <1501795433-982645-1-git-send-email-pasha.tatashin@oracle.com> <1501795433-982645-10-git-send-email-pasha.tatashin@oracle.com> <20170804053701.GA30068@ravnborg.org> From: Pasha Tatashin Message-ID: <4d98e852-15c0-1b66-a472-776ba1d51a6b@oracle.com> Date: Fri, 4 Aug 2017 09:50:57 -0400 MIME-Version: 1.0 In-Reply-To: <20170804053701.GA30068@ravnborg.org> Content-Type: text/plain; charset=utf-8; format=flowed List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi Sam, Thank you for looking at this. I will update patch description, and as you suggested replace memset() via static assert in next iteration. Pasha On 08/04/2017 01:37 AM, Sam Ravnborg wrote: > Hi Pavel. > > On Thu, Aug 03, 2017 at 05:23:47PM -0400, Pavel Tatashin wrote: >> Add an optimized mm_zero_struct_page(), so struct page's are zeroed without >> calling memset(). We do eight regular stores, thus avoid cost of membar. > > The commit message does no longer reflect the implementation, > and should be updated. > >> >> Signed-off-by: Pavel Tatashin >> Reviewed-by: Steven Sistare >> Reviewed-by: Daniel Jordan >> Reviewed-by: Bob Picco >> --- >> arch/sparc/include/asm/pgtable_64.h | 32 ++++++++++++++++++++++++++++++++ >> 1 file changed, 32 insertions(+) >> >> diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h >> index 6fbd931f0570..be47537e84c5 100644 >> --- a/arch/sparc/include/asm/pgtable_64.h >> +++ b/arch/sparc/include/asm/pgtable_64.h >> @@ -230,6 +230,38 @@ extern unsigned long _PAGE_ALL_SZ_BITS; >> extern struct page *mem_map_zero; >> #define ZERO_PAGE(vaddr) (mem_map_zero) >> >> +/* This macro must be updated when the size of struct page grows above 80 >> + * or reduces below 64. >> + * The idea that compiler optimizes out switch() statement, and only >> + * leaves clrx instructions or memset() call. >> + */ >> +#define mm_zero_struct_page(pp) do { \ >> + unsigned long *_pp = (void *)(pp); \ >> + \ >> + /* Check that struct page is 8-byte aligned */ \ >> + BUILD_BUG_ON(sizeof(struct page) & 7); \ > Would also be good to catch if sizeof > 80 so we do not silently > migrate to the suboptimal version (silent at build time). > Can you at build time catch if size is no any of: 64, 72, 80 > and simplify the below a little? > > Sam >