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From: Greg KH <gregkh@linuxfoundation.org>
To: Ganesh Mahendran <opensource.ganesh@gmail.com>
Cc: maco@android.com, tkjos@google.com, arve@android.com,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] android: binder: use VM_ALLOC to get vm area
Date: Mon, 22 Jan 2018 16:54:28 +0100	[thread overview]
Message-ID: <20180122155428.GB7714@kroah.com> (raw)
In-Reply-To: <1515552545-18311-1-git-send-email-opensource.ganesh@gmail.com>

On Wed, Jan 10, 2018 at 10:49:05AM +0800, Ganesh Mahendran wrote:
> VM_IOREMAP is used to access hardware through a mechanism called
> I/O mapped memory. Android binder is a IPC machanism which will
> not access I/O memory.
> 
> And VM_IOREMAP has alignment requiement which may not needed in
> binder.
>     __get_vm_area_node()
>     {
>     ...
>         if (flags & VM_IOREMAP)
>             align = 1ul << clamp_t(int, fls_long(size),
>                PAGE_SHIFT, IOREMAP_MAX_ORDER);
>     ...
>     }
> 
> This patch will save some kernel vm area, especially for 32bit os.
> 
> In 32bit OS, kernel vm area is only 240MB. We may got below
> error when launching a app:
> 
> <3>[ 4482.440053] binder_alloc: binder_alloc_mmap_handler: 15728 8ce67000-8cf65000 get_vm_area failed -12
> <3>[ 4483.218817] binder_alloc: binder_alloc_mmap_handler: 15745 8ce67000-8cf65000 get_vm_area failed -12
> 
> Signed-off-by: Ganesh Mahendran <opensource.ganesh@gmail.com>
> ----
> V3: update comments
> V2: update comments
> ---
>  drivers/android/binder_alloc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Martijn and Todd, any objections to this patch?

thanks,

greg k-h

  reply	other threads:[~2018-01-22 15:54 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-10  2:49 [PATCH v3] android: binder: use VM_ALLOC to get vm area Ganesh Mahendran
2018-01-22 15:54 ` Greg KH [this message]
2018-01-22 17:02   ` Todd Kjos
2018-01-22 18:55     ` Arve Hjønnevåg
2018-01-24  5:24       ` Ganesh Mahendran
2018-01-25  2:06     ` Ganesh Mahendran
2018-01-24 14:33   ` Martijn Coenen
2018-01-25  2:09     ` Ganesh Mahendran
2018-01-25  9:51       ` Greg KH

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