From mboxrd@z Thu Jan 1 00:00:00 1970 From: Haicheng Li Subject: Re: [PATCH 4/4] f2fs: optimize build_free_nids() Date: Wed, 8 May 2013 14:24:55 +0800 Message-ID: <20130508062455.GB8705@hli22-desktop> References: <1367853344-28938-1-git-send-email-haicheng.li@linux.intel.com> <1367853344-28938-5-git-send-email-haicheng.li@linux.intel.com> <1367922839.16581.42.camel@kjgkr> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: linux-kernel@vger.kernel.org, Haicheng Li , linux-fsdevel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net To: Jaegeuk Kim Return-path: Received: from mga01.intel.com ([192.55.52.88]:5482 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751031Ab3EHGZC (ORCPT ); Wed, 8 May 2013 02:25:02 -0400 Content-Disposition: inline In-Reply-To: <1367922839.16581.42.camel@kjgkr> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Tue, May 07, 2013 at 07:33:59PM +0900, Jaegeuk Kim wrote: > 2013-05-06 (=EC=9B=94), 23:15 +0800, Haicheng Li: > > diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c > > index 1fe3fe2..3136224 100644 > > --- a/fs/f2fs/node.c > > +++ b/fs/f2fs/node.c > > @@ -1342,6 +1342,8 @@ static void build_free_nids(struct f2fs_sb_in= fo *sbi) > > if (nid >=3D nm_i->max_nid) > > nid =3D 0; > > =20 > > + if (nm_i->fcnt > 2 * MAX_FREE_NIDS) > > + break; >=20 > Could you explain when this can happen? I'm thinking of this possible scenario: as we don't hold any spinlock to protect the context, add_free_nid() co= uld be=20 called by other thread anytime, e.g. by the gc_thread_func() in backgro= und. then nm_i->fcnt could be increased as 2 * MAX_FREE_NIDS while i < FREE_= NID_PAGES. Anything I misconsidered? > IMO, this is an unnecessary condition check, since the below conditio= n > that includes FREE_NID_PAGES already limits the number of free nids. > Thanks, hmm, the pros is that this check may possibly avoid some (< 4) unnecess= ary while-loop, the cons is that too many checks of (nm_i->fcnt > 2 * MAX_FREE_NIDS) would make the code looking messy and fragmentary... =20 > > if (i++ =3D=3D FREE_NID_PAGES) > > break; > > } >=20 > --=20 > Jaegeuk Kim > Samsung -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel= " in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html