From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hans Reiser Subject: Re: reiser4: first impression (vs xfs and jfs) Date: Tue, 06 Jun 2006 12:26:24 -0700 Message-ID: <4485D6E0.8090406@namesys.com> References: <20060523155102.GB25889@zero> <20060606134459.GA18513@zero> <1149604706.6389.40.camel@tribesman.namesys.com> <20060606153035.GF10672@HAL_5000D> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: list-help: list-unsubscribe: list-post: Errors-To: flx@namesys.com In-Reply-To: List-Id: Content-Type: text/plain; charset="us-ascii" To: PFC Cc: Clay Barnes , "Vladimir V. Saveliev" , reiserfs-list@namesys.com PFC wrote: > >> This may have been mentioned before, but perhaps there could be a >> "trickle-out" option along the lines of "if the hard drive is idle (and >> optionally only if it's spun up), slowly write out the changes to the >> disk structure." This could also be paired with keeping as much of the >> data in memory as necessary to mantain the speed boost that r4 gets from >> temporal locality of reference, possibly just giving it to the system >> cache. > > > Hm actually, this looks a lot like read-ahead algorithms, but > instead it's "write-ahead" : > > For instance : > - Sequential writes on large files should stream through the cache. > - Random writes or small file writes should be kept as long as > possible in dirty pages so they can be coalesced into larger writes > with a better disk layout on flush, or not written at all if it was > temp files from a make, for instance. > > Do the file copying programs open their output files with > O_SEQUENTIAL ? If so, there is information to exploit... > > You can change them to do so....