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>
