From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: [RFD] swsusp problem: Drivers allocate much memory during suspend (was: Re: 2.6.21-rc5: swsusp: Not enough free memory) Date: Sat, 14 Apr 2007 11:33:32 +0200 Message-ID: <200704141133.33366.rjw@sisk.pl> References: <460B6E4B.3060004@gmail.com> <200704140057.35829.rjw@sisk.pl> <1176505430.7112.216.camel@nigel.suspend2.net> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <1176505430.7112.216.camel@nigel.suspend2.net> Content-Disposition: inline List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-pm-bounces@lists.linux-foundation.org Errors-To: linux-pm-bounces@lists.linux-foundation.org To: Nigel Cunningham Cc: linux-pm@lists.osdl.org, Jiri Slaby , Pavel Machek , Linux kernel mailing list List-Id: linux-pm@vger.kernel.org On Saturday, 14 April 2007 01:03, Nigel Cunningham wrote: > Hi. > = > On Sat, 2007-04-14 at 00:57 +0200, Rafael J. Wysocki wrote: > > > > > Well, I'm not sure. First, we don't really know what the value o= f it should be > > > > > and this alone is a good enough reason for making it tunable, IMH= O. Second, I > > > > > think different systems may need different PAGES_FOR_IO and takin= g just the > > > > > maximum (even if we learn how much that actually is) seems to be = wasteful in > > > > = > > > > Well, it is wasteful as in "we save slightly smaller image than we > > > > could". That's okay with me. > > > = > > > No. If the driver can't allocate the memory, your call to device_susp= end > > > will fail. This isn't about image size but about success or failure to > > > hibernate. > > = > > If we take PAGES_FOR_IO to be the maximum over all possible configurati= ons > > that can hibernate, the majority of systems will just create smaller im= ages than > > they could have created for smaller PAGES_FOR_IO, but all of them will = be > > able to hibernate. :-) > = > You also use PAGES_FOR_IO in enough_free_mem. Say you set it to the 9000 > pages I mentioned before (35M). On a machine with 64 megabytes of > memory, you'll never be able to suspend because you'll never satisfy > = > free > nr_pages + PAGES_FOR_IO + meta Well, in fact our tunable would need to be independent of PAGES_FOR_IO so t= hat the memory shrinker could free some spare memory for the drivers. > I'll freely admit that 64 megabytes is tiny nowadays, but it's not > completely unknown. The point is really that you're effectively making > swsusp unusable for machines with RAM < (PAGES_FOR_IO * (say) 3). But > what do you set PAGES_FOR_IO to? There'll always be someone with > $WHIZ_BANG_CONFIG who is pushing to have the value increased, and every > increase knocks out more of your lowend users. Yes, that's why I said I wasn't sure whether or not the additional tunable = was needed. Still, with the notifiers we have a chance to handle the problem automatica= lly and the tunable would require the user to set the right value. Greetings, Rafael