Hi, > -----Original Message----- > From: Pavel Machek [mailto:pa...@ucw.cz] > Sent: Saturday, August 06, 2016 2:20 AM > To: PINTU KUMAR > Cc: 'Minchan Kim'; linux-kernel@vger.kernel.org; linux...@kvack.org; > jaejoon....@samsung.com; jy0.j...@samsung.com; vishnu...@samsung.com > Subject: Re: [linux-mm] Drastic increase in application memory usage with Kernel > version upgrade > > On Fri 2016-08-05 20:17:36, PINTU KUMAR wrote: > > Hi, > > > > On Fri, Aug 05, 2016 at 10:26:37AM +0530, PINTU KUMAR wrote: > > > > Hi All, > > > > > > > > For one of our ARM embedded product, we recently updated the > > > > Kernel version from 3.4 to 3.18 and we noticed that the same > > > > application memory usage (PSS value) gone up by ~10% and for > > > > some cases it even crossed ~50%. There is no change in platform > > > > part. All platform component was built with ARM 32-bit toolchain. > > > > However, the Kernel is changed from 32-bit to 64-bit. > > > > > > > > Is upgrading Kernel version and moving from 32-bit to 64-bit is > > > > such a risk? > > > > After the upgrade, what can we do further to reduce the > > > > application memory usage ? > > > > Is there any other factor that will help us to improve without > > > > major modifications in platform ? > > > > > > > > As a proof, we did a small experiment on our Ubuntu-32 bit machine. > > > > We upgraded Ubuntu Kernel version from 3.13 to 4.01 and we > > > > observed the following: > > > > ------------------------------------------------------------------ > > > > |UBUNTU-32 bit |Kernel 3.13 |Kernel 4.03 |DIFF | > > > > |CALCULATOR PSS |6057 KB |6466 KB |409 KB | > > > > ------------------------------------------------------------------ > > > > So, just by upgrading the Kernel version: PSS value for calculator > > > > is increased by 409KB. > > > > > > > > If anybody knows any in-sight about it please point out more > > > > details about the root cause. > > > > > > One of culprit is [8c6e50b0290c, mm: introduce vm_ops->map_pages()]. > > Ok. Thank you for your reply. > > So, if I revert this patch, will the memory usage be decreased for the > > processes with Kernel 3.18 ? > > I guess you should try it... > Thanks for the reply and confirmation. Our exact kernel version is: 3.18.14 And, we already have this patch: /* mm: do not call do_fault_around for non-linear fault Ingo Korb reported that "repeated mapping of the same file on tmpfs using remap_file_pages sometimes triggers a BUG at mm/filemap.c:202 when the process exits". He bisected the bug to d7c1755179b8 ("mm: implement ->map_pages for shmem/tmpfs"), although the bug was actually added by commit 8c6e50b0290c ("mm: introduce vm_ops->map_pages()"). */
So, I guess, reverting this patch (8c6e50b0290c), is not required ? But, still we have memory usage issue. > You may want to try the same kernel version, once in 32-bit and once in 64-bit > version. And you may consider moving to recent kernel. > Sorry, but moving to higher kernel version is not possible as of now. As it involves other BSP changes. We can only upgrades the relevant patches. However, as I said earlier, we even found the difference on Ubuntu 32-bit after moving from Kernel-3.13 to 4.0. So, I guess, this problem exists even in higher kernel version too. > Yes, 64-bit kernel will increase memory usage _of kernel_, but... > Ok, But ? Will it be major culprit ? Or higher kernel version is major culprit ? > > Pavel > -- > (english) http://www.livejournal.com/~pavelmachek > (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
