Messages in this thread Patch in this message | | | From | PINTU KUMAR <> | Subject | RE: [PATCH v3 1/1] kernel/sysctl.c: Add /proc/sys/vm/shrink_memory feature | Date | Wed, 22 Jul 2015 18:33:26 +0530 |
| |
Dear Mel, thank you very much for your comments and suggestions. I will drop this one and look on further improving direct_reclaim and compaction. Just few more comments below before I close.
Also, during this patch, I feel that the hibernation_mode part in shrink_all_memory can be corrected. So, can I separately submit the below patch? That is instead of hard-coding the hibernation_mode, we can get hibernation status using: system_entering_hibernation()
Please let me know your suggestion about this changes.
-#ifdef CONFIG_HIBERNATION +#if defined CONFIG_HIBERNATION || CONFIG_SHRINK_MEMORY /* * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of * freed pages. @@ -3576,12 +3580,16 @@ unsigned long shrink_all_memory(unsigned long nr_to_reclaim) .may_writepage = 1, .may_unmap = 1, .may_swap = 1, - .hibernation_mode = 1, }; struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask); struct task_struct *p = current; unsigned long nr_reclaimed;
+ if (system_entering_hibernation()) + sc.hibernation_mode = 1; + else + sc.hibernation_mode = 0; + p->flags |= PF_MEMALLOC; lockdep_set_current_reclaim_state(sc.gfp_mask); reclaim_state.reclaimed_slab = 0; @@ -3597,6 +3605,28 @@ unsigned long shrink_all_memory(unsigned long nr_to_reclaim) } #endif /* CONFIG_HIBERNATION */
> -----Original Message----- > From: Mel Gorman [mailto:mgorman@suse.de] > Sent: Monday, July 20, 2015 11:26 PM > To: PINTU KUMAR > Cc: akpm@linux-foundation.org; corbet@lwn.net; vbabka@suse.cz; > gorcunov@openvz.org; mhocko@suse.cz; emunson@akamai.com; > kirill.shutemov@linux.intel.com; standby24x7@gmail.com; > hannes@cmpxchg.org; vdavydov@parallels.com; hughd@google.com; > minchan@kernel.org; tj@kernel.org; rientjes@google.com; > xypron.glpk@gmx.de; dzickus@redhat.com; prarit@redhat.com; > ebiederm@xmission.com; rostedt@goodmis.org; uobergfe@redhat.com; > paulmck@linux.vnet.ibm.com; iamjoonsoo.kim@lge.com; ddstreet@ieee.org; > sasha.levin@oracle.com; koct9i@gmail.com; cj@linux.com; > opensource.ganesh@gmail.com; vinmenon@codeaurora.org; linux- > doc@vger.kernel.org; linux-kernel@vger.kernel.org; linux-mm@kvack.org; linux- > pm@vger.kernel.org; qiuxishi@huawei.com; Valdis.Kletnieks@vt.edu; > cpgs@samsung.com; pintu_agarwal@yahoo.com; vishnu.ps@samsung.com; > rohit.kr@samsung.com; iqbal.ams@samsung.com; pintu.ping@gmail.com; > pintu.k@outlook.com > Subject: Re: [PATCH v3 1/1] kernel/sysctl.c: Add /proc/sys/vm/shrink_memory > feature > > On Mon, Jul 20, 2015 at 09:43:02PM +0530, PINTU KUMAR wrote: > > Hi, > > > > Thank you all for reviewing the patch and providing your valuable > > comments and suggestions. > > During the ELC conference many people suggested to release the patch > > to mainline, so this patch, to get others opinion. > > > > Unfortunately, in my opinion it runs the risk of creating a different set of > problems. Either it needs to be run frequently to keep memory free which incurs > one set of penalties or it is used too late when there are > unmovable/unreclaimable pages preventing allocations succeeding in which case > you are back at the original problem.
Yes, I completely agree with you that it needs to be invoked at the right time. Running it too late is of no benefit.
> I see what you did and why it would work in some cases > but I think the main reason it works is because it's run frequently > enough so memory is never used. Yes, we ran frequently, but not so frequently and only when required. Actually, it gives us best result when calling shrink_memory plus compaction together, once after boot, and once during order-4 failure from kernel, or during suspend state. It reduced the slowpath count drastically (during 30 application launch test). VMSTAT WITHOUT WITH slowpath_entered 16659 1859 allocstall 298 149 pageoutrun 2699 1108 compact_stall 244 37 nr_free_cma 2560 2505
Anyways, I agree that if reclaimable pages or SWAP free is not enough, it does not yield good results.
> Grouping pages by mobility actually took > advantage of a similar property when it increased min_free_kbytes but that was > much more limited than adding a giant hammer for userspace to reclaim the > world. > > > If you have any more suggestions to experiment and verify please let me know. > > > > I believe I already did. If it's high-order reliability that is important then you need > to either reserve the memory or look at protecting the pages using grouping > pages by mobility. I pointed out what series to look at and the leader explains > how it could be adjusted further for the embedded case if necessary.
Thanks. I would definitely look into grouping pages by mobility and those series.
> > If it's latency you are interested in then reclaim/compaction needs to be modified > to be more aggressive when it is somehow detected that the high-order > allocation must succeed for functional correctness. In that case the relational > starting point would be to look at should_continue_reclaim and how it relates to > compaction. > Thanks. Definitely I will do a deep dive into should_continue_reclaim.
> > The suggestion was only to open up the shrink_all_memory API for some use > cases. > > > > I am not saying that it needs to be called continuously. It can be > > used only on certain condition and only when deemed necessary. > > The same technique is already used in hibernation to reduce the RAM > > snapshot image size. > > Reducing memory usage is not the same as guaranteeing that high-order pages > are available for allocation. > > -- > Mel Gorman > SUSE Labs
| |