linux-kernel - Re: Avoid high order memory allocating with kmalloc, when read large seq file

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Date:	Tue, 29 Jan 2013 13:49:22 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	xtu4 <xiaobing.tu@...el.com>
cc:	linux-kernel@...r.kernel.org, guifang.tang@...el.com,
	linX.z.chen@...el.com, Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: Avoid high order memory allocating with kmalloc, when read large
 seq file

On Tue, 29 Jan 2013, xtu4 wrote:

> Subject: [PATCH] [SEQ_FILE] Avoid high order memory allocating with kmalloc
>  when read large seq file
> 
> currently, when dumpstate access /proc/xxx/binder , this binder include lots
> of info,
> it will use seq_read in kernel, in this function, it will trigger high order
> memory alloc,
> when read binder info or other large file, this will cause memory presure when
> system
> don't have contious high order memory, it will lead to high kswap workload to
> reclaim the
> page. so change kmalloc to vmalloc, it can avoid contiously high order memory
> allocating.
> [ 4356.532357] dumpstate: page allocation failure: order:4, mode:0x40d0
> [ 4356.532400] Pid: 18256, comm: dumpstate Tainted: G         C
> 3.0.34-141128-g4be7088 #1
> [ 4356.532416] Call Trace:
> [ 4356.532443]  [<c185c836>] ? printk+0x1d/0x1f
> [ 4356.532467]  [<c12cde1f>] warn_alloc_failed+0xbf/0xf0
> [ 4356.532491]  [<c12d0aba>] __alloc_pages_nodemask+0x4ba/0x6a0
> [ 4356.532521]  [<c12d0d1c>] __get_free_pages+0x1c/0x30
> [ 4356.532541]  [<c12f51e1>] kmalloc_order_trace+0x21/0xd0
> [ 4356.532561]  [<c131d0f7>] ? seq_read+0x137/0x390
> [ 4356.532579]  [<c12f549a>] __kmalloc+0x20a/0x230
> [ 4356.532596]  [<c131d0f7>] ? seq_read+0x137/0x390
> [ 4356.532616]  [<c12d343c>] ? put_page+0x2c/0x40
> [ 4356.532634]  [<c12f4a7d>] ? kfree+0xcd/0x160
> [ 4356.532655]  [<c18656cd>] ? mutex_unlock+0xd/0x10
> [ 4356.532675]  [<c131d109>] seq_read+0x149/0x390
> [ 4356.532697]  [<c130062c>] vfs_read+0x8c/0x160
> [ 4356.532716]  [<c131cfc0>] ? seq_lseek+0x180/0x180
> [ 4356.532735]  [<c130073d>] sys_read+0x3d/0x70
> [ 4356.532755]  [<c1866e91>] syscall_call+0x7/0xb
> [ 4356.532777]  [<c1860000>] ? log_dir_items+0x33d/0x40c
> Signed-off-by: xiaobing tu <xiaobing.tu@...el.com>
> Signed-off-by: linX z chen <linX.z.chen@...el.com>
> Signed-off-by: guifang tang <guifang.tang@...el.com>
> Change-Id: I892c97d02cf25e59b23c9bc68dff754ea01c1d56
> ---
>  fs/seq_file.c |   18 +++++++++++++++---
>  1 files changed, 15 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/seq_file.c b/fs/seq_file.c
> index dba43c3..20b8e36 100644
> --- a/fs/seq_file.c
> +++ b/fs/seq_file.c
> @@ -209,8 +209,17 @@ ssize_t seq_read(struct file *file, char __user *buf,
> size_t size, loff_t *ppos)
>          if (m->count < m->size)
>              goto Fill;
>          m->op->stop(m, p);
> -        kfree(m->buf);
> -        m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
> +        if (m->size > 2 * PAGE_SIZE) {
> +            vfree(m->buf);
> +        } else
> +            kfree(m->buf);
> +        m->size <<= 1;
> +        if (m->size > 2 * PAGE_SIZE) {
> +            m->buf = vmalloc(m->size);
> +        } else
> +            m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);

I thought m->size was already shifted.

Your patch is severely mangled, please check out 
Documentation/SubmittingPatches and Documentation/email-clients.txt.

> +
> +
>          if (!m->buf)
>              goto Enomem;
>          m->count = 0;
> @@ -325,7 +334,10 @@ EXPORT_SYMBOL(seq_lseek);
>  int seq_release(struct inode *inode, struct file *file)
>  {
>      struct seq_file *m = file->private_data;
> -    kfree(m->buf);
> +    if (m->size > 2 * PAGE_SIZE) {
> +        vfree(m->buf);
> +    } else
> +        kfree(m->buf);
>      kfree(m);
>      return 0;
>  }
--
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