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

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Date:   Tue, 01 Aug 2017 21:00:20 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Yisheng Xie <xieyisheng1@...wei.com>, 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

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?

# grep -c "unpurged" /proc/vmallocinfo 
311

cheers