Thank you Masayoshi for verifying this work. I will submit it as you suggested. Pavel On Mon, Feb 5, 2018 at 9:14 AM, Masayoshi Mizuma <msys.mizuma@xxxxxxxxx> wrote: > Hello Pavel, > >> Yes, the patch is here: >> https://lkml.org/lkml/2018/1/12/600 > > I tested your patch in my box and it worked well. > Please feel free to add the following. > > Tested-by: Masayoshi Mizuma <m.mizuma@xxxxxxxxxxxxxx> > > You may repost the patch after adding your reply for > Andrew's comment as [PATCH 0/1]... > > - Masayoshi > > Wed, 31 Jan 2018 13:24:55 -0500 Pavel Tatashin wrote: >> Hi Koki, >> >> Yes, the patch is here: >> https://lkml.org/lkml/2018/1/12/600 >> >> It has not been reviewed yet. >> >> Pavel >> >> On Wed, Jan 31, 2018 at 12:28 PM, Koki.Sanagi@xxxxxxxxxxxxxx >> <Koki.Sanagi@xxxxxxxxxxxxxx> wrote: >>> Pavel, >>> >>> I assume you are working on the fix. >>> Do you have any progress ? >>> >>> Koki >>> >>>>> -----Original Message----- >>>>> From: Mel Gorman [mailto:mgorman@xxxxxxxxxxxxxxxxxxx] >>>>> Sent: Wednesday, December 06, 2017 5:50 AM >>>>> To: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> >>>>> Cc: Michal Hocko <mhocko@xxxxxxxxxx>; YASUAKI ISHIMATSU >>>>> <yasu.isimatu@xxxxxxxxx>; Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>; >>>>> Linux Memory Management List <linux-mm@xxxxxxxxx>; linux- >>>>> kernel@xxxxxxxxxxxxxxx; Sanagi, Koki <Koki.Sanagi@xxxxxxxxxxxxxx>; Steve >>>>> Sistare <steven.sistare@xxxxxxxxxx> >>>>> Subject: Re: [PATCH] mm, meminit: Serially initialise deferred memory if >>>>> trace_buf_size is specified >>>>> >>>>> On Wed, Nov 29, 2017 at 10:41:59PM -0500, Pavel Tatashin wrote: >>>>>> Hi Mel, >>>>>> >>>>>> Thank you very much for your feedback, my replies below: >>>>>> >>>>>>> A lack of involvement from admins is indeed desirable. For example, >>>>>>> while I might concede on using a disable-everything-switch, I would >>>>>>> not be happy to introduce a switch that specified how much memory >>>>>>> per node to initialise. >>>>>>> >>>>>>> For the forth approach, I really would be only thinking of a blunt >>>>>>> "initialise everything instead of going OOM". I was wary of making >>>>>>> things too complicated and I worried about some side-effects I'll cover later. >>>>>> >>>>>> I see, I misunderstood your suggestion. Switching to serial >>>>>> initialization when OOM works, however, boot time becomes >>>>>> unpredictable, with some configurations boot is fast with others it is >>>>>> slow. All of that depends on whether predictions in >>>>>> reset_deferred_meminit() were good or not which is not easy to debug >>>>>> for users. Also, overtime predictions in reset_deferred_meminit() can >>>>>> become very off, and I do not think that we want to continuously >>>>>> adjust this function. >>>>>> >>>>> >>>>> You could increase the probabilty of a report by doing a WARN_ON_ONCE if the >>>>> serialised meminit is used. >>>>> >>>>>>>> With this approach we could always init a very small amount of >>>>>>>> struct pages, and allow the rest to be initialized on demand as >>>>>>>> boot requires until deferred struct pages are initialized. Since, >>>>>>>> having deferred pages feature assumes that the machine is large, >>>>>>>> there is no drawback of having some extra byte of dead code, >>>>>>>> especially that all the checks can be permanently switched of via >>>>>>>> static branches once deferred init is complete. >>>>>>>> >>>>>>> >>>>>>> This is where I fear there may be dragons. If we minimse the number >>>>>>> of struct pages and initialise serially as necessary, there is a >>>>>>> danger that we'll allocate remote memory in cases where local memory >>>>>>> would have done because a remote node had enough memory. >>>>>> >>>>>> True, but is not what we have now has the same issue as well? If one >>>>>> node is gets out of memory we start using memory from another node, >>>>>> before deferred pages are initialized? >>>>>> >>>>> >>>>> It's possible but I'm not aware of it happening currently. >>>>> >>>>>> To offset that risk, it would be >>>>>>> necessary at boot-time to force allocations from local node where >>>>>>> possible and initialise more memory as necessary. That starts >>>>>>> getting complicated because we'd need to adjust gfp-flags in the >>>>>>> fast path with init-and-retry logic in the slow path and that could >>>>>>> be a constant penalty. We could offset that in the fast path by >>>>>>> using static branches >>>>>> >>>>>> I will try to implement this, and see how complicated the patch will >>>>>> be, if it gets too complicated for the problem I am trying to solve we >>>>>> can return to one of your suggestions. >>>>>> >>>>>> I was thinking to do something like this: >>>>>> >>>>>> Start with every small amount of initialized pages in every node. >>>>>> If allocation fails, initialize enough struct pages to cover this >>>>>> particular allocation with struct pages rounded up to section size but >>>>>> in every single node. >>>>>> >>>>> >>>>> Ok, just make sure it's all in the slow paths of the allocator when the alternative >>>>> is to fail the allocation. >>>>> >>>>>>> but it's getting more and >>>>>>> more complex for what is a minor optimisation -- shorter boot times >>>>>>> on large machines where userspace itself could take a *long* time to >>>>>>> get up and running (think database reading in 1TB of data from disk as it >>>>> warms up). >>>>>> >>>>>> On M6-32 with 32T [1] of memory it saves over 4 minutes of boot time, >>>>>> and this is on SPARC with 8K pages, on x86 it would be around of 8 >>>>>> minutes because of twice as many pages. This feature improves >>>>>> availability for larger machines quite a bit. Overtime, systems are >>>>>> growing, so I expect this feature to become a default configuration in >>>>>> the next several years on server configs. >>>>>> >>>>> >>>>> Ok, when developing the series originally, I had no machine even close to 32T of >>>>> memory. >>>>> >>>>> -- >>>>> Mel Gorman >>>>> SUSE Labs >>> >>> -- >>> 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 hrefmailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> > > -- > 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> -- 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>
