From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from nausicaa2.coritel.it (host254-130-static.190-82-b.business.telecomitalia.it [82.190.130.254]) by ozlabs.org (Postfix) with ESMTP id 3E370DE130 for ; Thu, 17 Jul 2008 22:03:44 +1000 (EST) Message-ID: <487F35A4.7050203@coritel.it> Date: Thu, 17 Jul 2008 14:05:56 +0200 From: Marco Stornelli MIME-Version: 1.0 To: Ruksen INANIR Subject: Re: increase lowmem value for ppc References: <487F1FD2.7090909@gmail.com> <487F297B.4070806@coritel.it> <487F2B4C.7070409@coritel.it> <487F2B7D.6080109@gmail.com> <487F2E79.1030102@coritel.it> <487F3248.9080405@gmail.com> In-Reply-To: <487F3248.9080405@gmail.com> Content-Type: text/plain; charset=us-ascii; format=flowed Cc: linuxppc-embedded@ozlabs.org List-Id: Linux on Embedded PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Ruksen INANIR ha scritto: > > Thanks for your comments. > I tried the highmem option but one of the device drivers does not > support highmem, so it did not work. Strange....you can try to look at it, it could be only some GFP flag. > the only choice for me is to increase the lowmem to 1520 MB. the maximum > lowmem value i reached succesfully is 1503 MB. but any value more than > 1503 results kernel not able to load kernel modules. Mmmm....have you tried a stress test? It sounds like a bit strange that the kernel works well with this mapping but without other modification. > Upgrading to a 2.6.x kernel may solve the problem, but it needs a lot of > effort. Does 2.6.x kernel support 2G physical memory? > It's the same. Some architecture have 36-bit addressing, but I don't know if the latest kernel has the support for this feature for powerpc. > > > > Marco Stornelli wrote: >> Ruksen INANIR ha scritto: >>> >>> Is there any side effects of changing the address splitting? >> >> Yes, in this way the application address space is smaller than normal. >> Some big applications (for example same dbms) might not work. Usually >> with 2G/2G most of the applications work well. >> >>> What should i change for 2G/2G splitting? should i shift the kernel >>> start? >>> Thanks >>> >> Yes in advanced options of the kernel menu, but sometimes it's not >> easy. Sometimes ago I had to do the same thing but I have to change >> the kernel code because some operations were hard-coded. Be careful >> because it's not an easy operation. However I'd suggest you to use the >> highmem, the memory performance are worse than direct memory mapping, >> but usually it's not a problem because the overhead is low. >> >>> >>> Marco Stornelli wrote: >>>> Marco Stornelli ha scritto: >>>>> Ruksen INANIR ha scritto: >>>>>> >>>>>> Is there a way to increase the lowmem value for ppc. The >>>>>> MAX_LOW_MEM is defined as max 768 MB. But a value around 1.5 G >>>>>> works with no problem. But when i try to increase this value to >>>>>> 1520 or more, kernel complaints about no space for memory >>>>>> allocation when loading kernel modules. >>>>>> I do not want to use HIGHMEM config. What is the max lowmem value >>>>>> for a ppc system? What other setting are needed to use 1520 MB (or >>>>>> more) as lowmem . >>>>>> The ppc card has 2G on board memory. 2.4.22 kernel is used. >>>>>> >>>>>> Thanks >>>>>> _______________________________________________ >>>>>> Linuxppc-embedded mailing list >>>>>> Linuxppc-embedded@ozlabs.org >>>>>> https://ozlabs.org/mailman/listinfo/linuxppc-embedded >>>>>> >>>>> With 32-bit arch you may not use more than 1GB to map the memory >>>>> (minus some space for some kernel operation). The value of 768MB >>>>> was not there by chance. >>>>> >>>> Only an additional comment: I meant with the address splitting >>>> 3G/1G. To map more than 1GB, you have to change the splitting 2G/2G >>>> for example. >>>> >>> >>> _______________________________________________ >>> Linuxppc-embedded mailing list >>> Linuxppc-embedded@ozlabs.org >>> https://ozlabs.org/mailman/listinfo/linuxppc-embedded >>> >> >> > > _______________________________________________ > Linuxppc-embedded mailing list > Linuxppc-embedded@ozlabs.org > https://ozlabs.org/mailman/listinfo/linuxppc-embedded > -- Marco Stornelli Embedded Software Engineer CoRiTeL - Consorzio di Ricerca sulle Telecomunicazioni http://www.coritel.it marco.stornelli@coritel.it +39 06 72582838