linux-kernel - RE: Re: Re: [PATCH 1/1] stackdepot: interface to check entries and size of stackdepot.

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Date:   Fri, 24 Nov 2017 13:30:25 +0000
From:   Vaneet Narang <v.narang@...sung.com>
To:     Michal Hocko <mhocko@...nel.org>
CC:     Dmitry Vyukov <dvyukov@...gle.com>,
        Maninder Singh <maninder1.s@...sung.com>,
        "kstewart@...uxfoundation.org" <kstewart@...uxfoundation.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "jkosina@...e.cz" <jkosina@...e.cz>,
        "pombredanne@...b.com" <pombredanne@...b.com>,
        "jpoimboe@...hat.com" <jpoimboe@...hat.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "vbabka@...e.cz" <vbabka@...e.cz>,
        "guptap@...eaurora.org" <guptap@...eaurora.org>,
        "vinmenon@...eaurora.org" <vinmenon@...eaurora.org>,
        AMIT SAHRAWAT <a.sahrawat@...sung.com>,
        PANKAJ MISHRA <pankaj.m@...sung.com>,
        Lalit Mohan Tripathi <lalit.mohan@...sung.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        kasan-dev <kasan-dev@...glegroups.com>
Subject: RE: Re: Re: [PATCH 1/1] stackdepot: interface to check entries and
 size of stackdepot.

Hi Michal,

>> We have been getting similar kind of such entries and eventually
>> stackdepot reaches Max Cap. So we found this interface useful in debugging
>> stackdepot issue so shared in community.
 
>Then use it for internal debugging and provide a code which would scale
>better on smaller systems. We do not need this in the kernel IMHO. We do
>not merge all the debugging patches we use for internal development.
` 
Not just debugging but this information can also be used to profile and tune stack depot. 
Getting count of stack entries would help in deciding hash table size and 
page order used by stackdepot. 

For less entries, bigger hash table and higher page order slabs might not be required as 
maintained by stackdepot. As i already mentioned smaller size hashtable can be choosen and 
similarly lower order  pages can be used for slabs.

If you think its useful, we can share scalable patch to configure below two values based on 
number of stack entries dynamically.

#define STACK_ALLOC_ORDER 2 
#define STACK_HASH_SIZE (1L << STACK_HASH_ORDER)


Regards,
Vaneet Narang