From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id E26EC6B01EE for ; Fri, 2 Apr 2010 18:05:54 -0400 (EDT) Date: Fri, 2 Apr 2010 15:05:11 -0700 From: Andrew Morton Subject: Re: [RESEND][PATCH] __isolate_lru_page:skip unneeded "not" Message-Id: <20100402150511.6f71fbfd.akpm@linux-foundation.org> In-Reply-To: <1270129055-3656-1-git-send-email-lliubbo@gmail.com> References: <1270129055-3656-1-git-send-email-lliubbo@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Bob Liu Cc: linux-mm@kvack.org, kosaki.motohiro@jp.fujitsu.com List-ID: On Thu, 1 Apr 2010 21:37:35 +0800 Bob Liu wrote: > PageActive(page) will return int 0 or 1, mode is also int 0 or 1, > they are comparible so "not" is unneeded to be sure to boolean > values. > I also collected the ISOLATE_BOTH check together. > > Signed-off-by: Bob Liu > --- > mm/vmscan.c | 15 +++++---------- > 1 files changed, 5 insertions(+), 10 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index e0e5f15..ce9ee85 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -862,16 +862,11 @@ int __isolate_lru_page(struct page *page, int mode, int file) > if (!PageLRU(page)) > return ret; > > - /* > - * When checking the active state, we need to be sure we are > - * dealing with comparible boolean values. Take the logical not > - * of each. > - */ You deleted a spelling mistake too! > - if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode)) > - return ret; > - > - if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file) > - return ret; > + if (mode != ISOLATE_BOTH) { > + if ((PageActive(page) != mode) || > + (page_is_file_cache(page) != file)) > + return ret; > + } The compiler should be able to avoid testing for ISOLATE_BOTH twice, and I think the previous code layout was superior: if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode)) return ret; if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file) return ret; Because it gives us nice places to put a comment explaining what the code is doing, whereas making it a more complex single expression: if (mode != ISOLATE_BOTH) { if ((PageActive(page) != mode) || (page_is_file_cache(page) != file)) return ret; } makes clearly commenting each test more difficult. Yeah, there's no comment there at present. But that's because we suck - I'm sure someone is working on it ;) -- 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