From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from firewall.hyperwave.com (firewall.hyperwave.com [129.27.200.34]) by kvack.org (8.8.7/8.8.7) with ESMTP id IAA11073 for ; Thu, 27 Aug 1998 08:43:50 -0400 Date: Thu, 27 Aug 1998 14:43:31 +0200 (MET DST) Message-Id: <199808271243.OAA28073@hwal02.hyperwave.com> From: Bernhard Heidegger MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Subject: Re: [PATCH] 498+ days uptime In-Reply-To: <87emu2zkc0.fsf@atlas.CARNet.hr> References: <199808262153.OAA13651@cesium.transmeta.com> <87ww7v73zg.fsf@atlas.CARNet.hr> <199808271207.OAA15842@hwal02.hyperwave.com> <87emu2zkc0.fsf@atlas.CARNet.hr> Sender: owner-linux-mm@kvack.org To: Zlatko.Calusic@CARNet.hr Cc: Bernhard Heidegger , "H. Peter Anvin" , Linux Kernel List , Linux-MM List List-ID: >>>>> ">" == Zlatko Calusic writes: >> Bernhard Heidegger writes: >> >>>>> ">" == Zlatko Calusic writes: >> >> >> "H. Peter Anvin" writes: >> >> > >> >> > bdflush yes, but update is not obsolete. >> >> > >> >> > It is still needed if you want to make sure data (and metadata) >> >> > eventually gets written to disk. >> >> > >> >> > Of course, you can run without update, but then don't bother if you >> >> > lose file in system crash, even if you edited it and saved it few >> >> > hours ago. :) >> >> > >> >> > Update is very important if you have lots of RAM in your computer. >> >> > >> >> >> >> Oh. I guess my next question then is "why", as why can't this be done >> >> by kflushd as well? >> >> >> >> >> To tell you the truth, I'm not sure why, these days. >> >> >> I thought it was done this way (update running in userspace) so to >> >> have control how often buffers get flushed. But, I believe bdflush >> >> program had this functionality, and it is long gone (as you correctly >> >> noticed). >> >> IMHO, update/bdflush (in user space) calls sys_bdflush regularly. This >> function (fs/buffer.c) calls sync_old_buffers() which itself sync_supers >> and sync_inodes before it goes through the dirty buffer lust (to write >> some dirty buffers); the kflushd only writes some dirty buffers dependent >> on the sysctl parameters. >> If I'm wrong, please feel free to correct me! >> >> You are not wrong. >> Update flushes metadata blocks every 5 seconds, and data block every >> 30 seconds. My version of update (something around Slakware 3.4) does the following: 1.) calls bdflush(1,0) (fs/buffer.c:sys_bdflush) which will call sync_old_buffers() and return 2.) only if the bdflush(1,0) fails (it returns < 0) it returns to the old behavior of sync()ing every 30 seconds But case 2) should only happen on really old kernels; on newer kernels (I'm using 2.0.34) the bdflush() should never fail. But as I told, sync_old_buffers() do: 1.) sync_supers(0) 2.) sync_inodes(0) 3.) go through dirty buffer list and may flush some buffers Conclusion: the meta data get synced every 5 seconds and some buffers may be flushed. >> Questions is why can't this functionality be integrated in the kernel, >> so we don't have to run yet another daemon? Good question, but I've another one: IMHO sync_old_buffers (especially the for loop) do similar things as the kflushd. Why?? Is it possible to reduce the sync_old_buffers() routine to soemthing like: { sync_supers(0); sync_inodes(0); } ?? Bernhard get my pgp key from a public keyserver (keyID=0x62446355) ----------------------------------------------------------------------------- Bernhard Heidegger bheide@hyperwave.com Hyperwave Software Research & Development Schloegelgasse 9/1, A-8010 Graz Voice: ++43/316/820918-25 Fax: ++43/316/820918-99 ----------------------------------------------------------------------------- -- This is a majordomo managed list. To unsubscribe, send a message with the body 'unsubscribe linux-mm me@address' to: majordomo@kvack.org