On Wed, Aug 10, 2016 at 6:56 PM, PINTU KUMAR <pintu.k@xxxxxxxxxxx> wrote: > Hi, > >> -----Original Message----- >> From: Pavel Machek [mailto:pavel@xxxxxx] >> Sent: Saturday, August 06, 2016 2:20 AM >> To: PINTU KUMAR >> Cc: 'Minchan Kim'; linux-kernel@xxxxxxxxxxxxxxx; linux-mm@xxxxxxxxx; >> jaejoon.seo@xxxxxxxxxxx; jy0.jeon@xxxxxxxxxxx; vishnu.ps@xxxxxxxxxxx >> 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. > I had observed the PSS increase with 3.18, and that was because of the faultaround patch which MInchan mentioned. Without reverting the patch you can just try reducing fault_around_bytes (mm/memory.c) to PAGE_SIZE. That should bring down the PSS. Thanks, Vinayak -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>