From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benny Halevy Subject: Re: [pnfs] 3-word attributes encoding Date: Tue, 31 Mar 2009 23:00:50 +0300 Message-ID: <49D27672.9060007@panasas.com> References: <49D0D931.2060808@panasas.com> <20090331014439.GA7273@fieldses.org> <49D26298.6070507@panasas.com> <20090331194215.GE20756@fieldses.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Cc: NFS list , pNFS Mailing List , Trond Myklebust To: "J. Bruce Fields" Return-path: Received: from gw-ca.panasas.com ([209.116.51.66]:10336 "EHLO laguna.int.panasas.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755222AbZCaUAz (ORCPT ); Tue, 31 Mar 2009 16:00:55 -0400 In-Reply-To: <20090331194215.GE20756@fieldses.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Mar. 31, 2009, 22:42 +0300, "J. Bruce Fields" wrote: > On Tue, Mar 31, 2009 at 09:36:08PM +0300, Benny Halevy wrote: >> On Mar. 31, 2009, 4:44 +0300, "J. Bruce Fields" wrote: >>> On Mon, Mar 30, 2009 at 05:37:37PM +0300, Benny Halevy wrote: >>>> Bruce, >>>> >>>> As I mentioned in a reply to Trond, >>>> "nfsd41: support for 3-word long attribute bitmask" >>>> changes the server fattr encoding logic so it may send >>>> back a bitmap of length 1, even if the client sent a >>>> bitmap of length 2, if the second word of the bitmap >>>> is zero. Although I think this a valid implementation >>>> and other servers may do the same, it seems sub-optimal >>>> for the client's decoding of acl of fs_locations. >>> "suboptimal" means it does some extra memcpy'ing? >> Yes, I believe so. >> >>>> It's pretty easy to revert to the old behavior on the server >>>> by always returning at least two bitmap words, or, if we >>>> keep the bitmap length, not just the val, in nfsd4_decode_bitmap >>>> we can return a bitmap of the same length in the reply. >>> Odd thing to have to do, but OK. --b. >> What would you prefer to do? >> Revert to old behavior by returning at least two bitmap words >> or use the args bitmap length for encoding the res? > > Whichever requires the least code? I don't know. The former seems simpler to code. > > If the client really needs this, then it needs to be agreed on by more > than just the linux server. It's unfortunate if making this arbitrary > undocumented choice of result encoding makes a significant difference to > the client's performance. I think that currently it affects only getacl and I have no measurements of to what extent the effect of performance is. Benny > > --b.