From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Tomas Subject: Re: Reviewing ext3 improvement patches (delalloc, mballoc, extents) Date: Mon, 14 Mar 2005 18:43:02 +0300 Message-ID: References: <20050303083349.GA4896@in.ibm.com> <1109898734.4961.11.camel@dyn318077bld.beaverton.ibm.com> <1109900773.4637.9.camel@dyn318043bld.beaverton.ibm.com> <20050314053658.A12360@almesberger.net> <20050314090414.GA4164@in.ibm.com> <20050314120240.K12802@almesberger.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Suparna Bhattacharya , Mingming Cao , Badari Pulavarty , ext2-devel , linux-fsdevel@vger.kernel.org, Alex Tomas , abiss-general@lists.sourceforge.net To: Werner Almesberger In-Reply-To: <20050314120240.K12802@almesberger.net> (Werner Almesberger's message of "Mon, 14 Mar 2005 12:02:40 -0300") Sender: ext2-devel-admin@lists.sourceforge.net Errors-To: ext2-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , List-Archive: List-Id: linux-fsdevel.vger.kernel.org >>>>> Werner Almesberger (WA) writes: WA> Do you plan to reserve space as "blocks, somewhere", or as "these WA> specific on-disk locations" ? In ABISS, we did something of the WA> latter kind (in order to make large contiguous allocations also on WA> FAT), and it turned out to be a big mess, because ABISS needed too WA> much support from the file system driver. So we just scrapped that WA> bit :-) I see no reason to reserve specific block in ->prepare/->commit in delayed allocation case. We already do this with reservation. The sole point of delayed allocation is to allocate many blocks at once: to minimize fragmentation, to decrease allocator involvement, to avoid allocation at all if the file gets truncated quickly. WA> The main parts: we added a new page flag, PG_delalloc, which WA> basically tells everyone to stay away from that page. There are WA> two purposes: (a) to make sure no allocation happens unless WA> explicitly requested, and (b) prevent the page from being written WA> back while it is still in ABISS' playout buffer. The reason for WA> (b) is that the page gets locked during writeback, which could WA> cause delays if the ABISS-using application then decides to WA> access the page. locked during writeback? PG_writeback should be used instead of PG_locked. thanks, Alex ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click