Messages in this thread | | | Date | Tue, 08 Mar 2016 12:03:12 +0800 | From | Hanjun Guo <> | Subject | Re: Suspicious error for CMA stress test |
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On 03/07/2016 04:16 PM, Leizhen (ThunderTown) wrote: > > > On 2016/3/7 12:34, Joonsoo Kim wrote: >> On Fri, Mar 04, 2016 at 03:35:26PM +0800, Hanjun Guo wrote: >>> On 2016/3/4 14:38, Joonsoo Kim wrote: >>>> On Fri, Mar 04, 2016 at 02:05:09PM +0800, Hanjun Guo wrote: >>>>> On 2016/3/4 12:32, Joonsoo Kim wrote: >>>>>> On Fri, Mar 04, 2016 at 11:02:33AM +0900, Joonsoo Kim wrote: >>>>>>> On Thu, Mar 03, 2016 at 08:49:01PM +0800, Hanjun Guo wrote: >>>>>>>> On 2016/3/3 15:42, Joonsoo Kim wrote: >>>>>>>>> 2016-03-03 10:25 GMT+09:00 Laura Abbott <labbott@redhat.com>: >>>>>>>>>> (cc -mm and Joonsoo Kim) >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> On 03/02/2016 05:52 AM, Hanjun Guo wrote: >>>>>>>>>>> Hi, >>>>>>>>>>> >>>>>>>>>>> I came across a suspicious error for CMA stress test: >>>>>>>>>>> >>>>>>>>>>> Before the test, I got: >>>>>>>>>>> -bash-4.3# cat /proc/meminfo | grep Cma >>>>>>>>>>> CmaTotal: 204800 kB >>>>>>>>>>> CmaFree: 195044 kB >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> After running the test: >>>>>>>>>>> -bash-4.3# cat /proc/meminfo | grep Cma >>>>>>>>>>> CmaTotal: 204800 kB >>>>>>>>>>> CmaFree: 6602584 kB >>>>>>>>>>> >>>>>>>>>>> So the freed CMA memory is more than total.. >>>>>>>>>>> >>>>>>>>>>> Also the the MemFree is more than mem total: >>>>>>>>>>> >>>>>>>>>>> -bash-4.3# cat /proc/meminfo >>>>>>>>>>> MemTotal: 16342016 kB >>>>>>>>>>> MemFree: 22367268 kB >>>>>>>>>>> MemAvailable: 22370528 kB >>>>>>>> [...] >>>>>>>>>> I played with this a bit and can see the same problem. The sanity >>>>>>>>>> check of CmaFree < CmaTotal generally triggers in >>>>>>>>>> __move_zone_freepage_state in unset_migratetype_isolate. >>>>>>>>>> This also seems to be present as far back as v4.0 which was the >>>>>>>>>> first version to have the updated accounting from Joonsoo. >>>>>>>>>> Were there known limitations with the new freepage accounting, >>>>>>>>>> Joonsoo? >>>>>>>>> I don't know. I also played with this and looks like there is >>>>>>>>> accounting problem, however, for my case, number of free page is slightly less >>>>>>>>> than total. I will take a look. >>>>>>>>> >>>>>>>>> Hanjun, could you tell me your malloc_size? I tested with 1 and it doesn't >>>>>>>>> look like your case. >>>>>>>> I tested with malloc_size with 2M, and it grows much bigger than 1M, also I >>>>>>>> did some other test: >>>>>>> Thanks! Now, I can re-generate erronous situation you mentioned. >>>>>>> >>>>>>>> - run with single thread with 100000 times, everything is fine. >>>>>>>> >>>>>>>> - I hack the cam_alloc() and free as below [1] to see if it's lock issue, with >>>>>>>> the same test with 100 multi-thread, then I got: >>>>>>> [1] would not be sufficient to close this race. >>>>>>> >>>>>>> Try following things [A]. And, for more accurate test, I changed code a bit more >>>>>>> to prevent kernel page allocation from cma area [B]. This will prevent kernel >>>>>>> page allocation from cma area completely so we can focus cma_alloc/release race. >>>>>>> >>>>>>> Although, this is not correct fix, it could help that we can guess >>>>>>> where the problem is. >>>>>> More correct fix is something like below. >>>>>> Please test it. >>>>> Hmm, this is not working: >>>> Sad to hear that. >>>> >>>> Could you tell me your system's MAX_ORDER and pageblock_order? >>>> >>> >>> MAX_ORDER is 11, pageblock_order is 9, thanks for your help! >> >> Hmm... that's same with me. >> >> Below is similar fix that prevents buddy merging when one of buddy's >> migrate type, but, not both, is MIGRATE_ISOLATE. In fact, I have >> no idea why previous fix (more correct fix) doesn't work for you. >> (It works for me.) But, maybe there is a bug on the fix >> so I make new one which is more general form. Please test it. > > Hi, > Hanjun Guo has gone to Tailand on business, so I help him to run this patch. The result > shows that the count of "CmaFree:" is OK now.
Thanks Leizhen :)
> But sometimes printed some information as below: > > alloc_contig_range: [28500, 28600) PFNs busy > alloc_contig_range: [28300, 28380) PFNs busy
I think it's not a problem for the stress test, as it's the lock not released yet.
Thanks Hanjun
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