From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <3C63091A.4D9EA2D8@mvista.com> Date: Thu, 07 Feb 2002 16:09:14 -0700 From: "Mark A. Greer" MIME-Version: 1.0 To: Val Henson Cc: Benjamin Herrenschmidt , linuxppc-dev@lists.linuxppc.org Subject: Re: Highmem on PPC? References: <20020205115618.D6834@boardwalk> <20020205193316.19866@smtp.wanadoo.fr> <20020207144308.C19569@boardwalk> <3C62F74F.DE090C2C@mvista.com> <20020207145844.F19569@boardwalk> Content-Type: text/plain; charset=us-ascii Sender: owner-linuxppc-dev@lists.linuxppc.org List-Id: Val Henson wrote: > On Thu, Feb 07, 2002 at 02:53:19PM -0700, Mark A. Greer wrote: > > > > Val Henson wrote: > > > > > Also, I don't think this was a particularly good test of highmem since > > > I don't think many bounce buffers were used, or that the kernel had > > > much reason to map/unmap many highmem pages. Unfortunately, my SCSI > > > controller isn't working quite right and I can't test with a hard disk > > > as a result. Any ideas for stressing the system harder? > > > > You could try lowering max_low_mem. You can do this by setting "Code > > maturity level option"/"Prompt for advanced kernel configuration options" > > and then going under where you selected HIGH_MEM and setting max_low_mem > > size to something small. > > > > It will likely take some trial and error to get it stressed enough. > > You'll have to start a bunch or processes and look at where they're > > getting their memory > > See, I don't think that user processes using highmem pages is testing > highmem much. So we have user pages mapped by PTE's - what's changed? > Not a whole lot. It's when we use bounce buffers in the kernel or ask > the kernel to map user pages or otherwise trigger the kmap/kunmap code > that I'm interested in. I agree. What I had in mind was causing the kernel to kmap pages for some reason like to copy user data into the buffer cache of a block device (see generic_file_write). I would make a pgm to allocate some mem (like the size of your lowmem), mlock it down, then fork some processes that do short writes to a block device or something like that. I think that would do it. Did you mentioned that your scsi ctlr or drive was bad? If so, you'll have to find some other block device, /dev/ram? maybe?? Mark ** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/