From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Zarochentsev Subject: Re: [PATCH] reiserfs: on-demand bitmap loading (testing only) Date: Fri, 8 Jul 2005 09:35:28 +0400 Message-ID: <200507080935.28944.zam@namesys.com> References: <42CC4B7F.2070506@suse.com> <42CC5F1E.6060505@namesys.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: list-help: list-unsubscribe: list-post: Errors-To: flx@namesys.com In-Reply-To: <42CC5F1E.6060505@namesys.com> Content-Disposition: inline List-Id: Content-Type: text/plain; charset="us-ascii" To: Hans Reiser , Elena Gryaznova Cc: reiserfs-list@namesys.com, Jeff Mahoney On Thursday 07 July 2005 02:45, Hans Reiser wrote: > Jeff, are you sure that you need this code to exist? Here are the > problems I see: > > for the average case, it is suboptimal. The seeks to the bitmaps > are far more expensive than the averaged cost of keeping them in ram. It would be good to see the benchmark results which your opinion is based on. I know that on-demand bitmap loading in reiser4 was under suspicion several times but I don't remember any benchmark results which showed a slowdown regarding that. > > for 16TB filesystems, they will have plenty of budget for ram > > it complicates code if it has to worry about such things as not > enough clean memory for holding bitmaps, etc. > > It is more appropriate to write this kind of code for the > development branch which is V4. This kind of code is likely to have > hard to test and hit bugs. > Lena, may you check how the bitmap on-demand loading patch affects, say, mongo results for reiserfs? Thanks, Alex.