linux-kernel - Re: [PATCH v2] vmalloc: show more detail info in vmallocinfo for clarify

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Message-ID: <6f3c8e69-b2af-d23c-b226-805faf7efd89@huawei.com>
Date:   Tue, 1 Aug 2017 20:36:47 +0800
From:   Yisheng Xie <xieyisheng1@...wei.com>
To:     Michael Ellerman <mpe@...erman.id.au>, <akpm@...ux-foundation.org>
CC:     <mhocko@...e.com>, <zijun_hu@....com>, <mingo@...nel.org>,
        <thgarnie@...gle.com>, <kirill.shutemov@...ux.intel.com>,
        <aryabinin@...tuozzo.com>, <chris@...is-wilson.co.uk>,
        <tim.c.chen@...ux.intel.com>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>, <guohanjun@...wei.com>
Subject: Re: [PATCH v2] vmalloc: show more detail info in vmallocinfo for
 clarify

Hi Michael,

Thanks for comment!
On 2017/8/1 19:00, Michael Ellerman wrote:
> Yisheng Xie <xieyisheng1@...wei.com> writes:
> 
>> When ioremap a 67112960 bytes vm_area with the vmallocinfo:
>>  [..]
>>  0xec79b000-0xec7fa000  389120 ftl_add_mtd+0x4d0/0x754 pages=94 vmalloc
>>  0xec800000-0xecbe1000 4067328 kbox_proc_mem_write+0x104/0x1c4 phys=8b520000 ioremap
>>
>> we get the result:
>>  0xf1000000-0xf5001000 67112960 devm_ioremap+0x38/0x7c phys=40000000 ioremap
>>
>> For the align for ioremap must be less than '1 << IOREMAP_MAX_ORDER':
>> 	if (flags & VM_IOREMAP)
>> 		align = 1ul << clamp_t(int, get_count_order_long(size),
>> 			PAGE_SHIFT, IOREMAP_MAX_ORDER);
>>
>> So it makes idiot like me a litter puzzle why jump the vm_area from
>> 0xec800000-0xecbe1000 to 0xf1000000-0xf5001000, and leave
>> 0xed000000-0xf1000000 as a big hole.
>>
>> This is to show all of vm_area, including which is freeing but still in
>> vmap_area_list, to make it more clear about why we will get
>> 0xf1000000-0xf5001000 int the above case. And we will get the
>> vmallocinfo like:
>>  [..]
>>  0xec79b000-0xec7fa000  389120 ftl_add_mtd+0x4d0/0x754 pages=94 vmalloc
>>  0xec800000-0xecbe1000 4067328 kbox_proc_mem_write+0x104/0x1c4 phys=8b520000 ioremap
>>  [..]
>>  0xece7c000-0xece7e000    8192 unpurged vm_area
>>  0xece7e000-0xece83000   20480 vm_map_ram
>>  0xf0099000-0xf00aa000   69632 vm_map_ram
> 
> My vmallocinfo is full of these unpurged areas, should I be worried?

The unpurged areas is a lazy free vm area, which maybe free at anytime. e.g. if the
nr_lazy(count in pages) is bigger than lazy_max_pages(), these area will be purged
and free.

So I think you do not have worried about it.

Thanks
Yisheng Xie

> 
> # grep -c "unpurged" /proc/vmallocinfo 
> 311
> 
> cheers
> 
> .
>