Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: lib/genalloc
To:     Stephen Bates <sbates@raithlin.com>,
        "danielmentz@google.com" <danielmentz@google.com>,
        "mathieu.desnoyers@efficios.co" <mathieu.desnoyers@efficios.co>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Laura Abbott <labbott@redhat.com>
References: <a170cf65-6884-3592-1de9-4c235888cc8a@intel.com>
 <4DECD467-AD45-419D-8F0F-1456863274FD@raithlin.com>
From:   Alexey Skidanov <alexey.skidanov@intel.com>
Message-ID: <d127f28f-71fe-c175-c0e4-a368ff1d01a1@intel.com>
Date:   Thu, 1 Nov 2018 19:08:50 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.2.1
MIME-Version: 1.0
In-Reply-To: <4DECD467-AD45-419D-8F0F-1456863274FD@raithlin.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


On 11/1/18 18:48, Stephen  Bates wrote:
>>    I use gen_pool_first_fit_align() as pool allocation algorithm allocating
>>    buffers with requested alignment. But if a chunk base address is not
>>    aligned to the requested alignment(from some reason), the returned
>>    address is not aligned too.
>     
> Alexey
> 
> Can you try using gen_pool_first_fit_order_align()? Will that give you the alignment you need?
> 
> Stephen
>     
> 
I think it will not help me. Let's assume that the chunk base address is
0x2F400000 and I want to allocate 16MB aligned buffer. I get back the
0x2F400000. I think it happens because of this string in the
gen_pool_alloc_algo():

addr = chunk->start_addr + ((unsigned long)start_bit << order);

and the gen_pool_first_fit_align() implementation that doesn't take into
account the "incorrect" chunk base alignment.

It might be easily fixed, by rounding the start address up (0x2F400000
-> 0x30000000) and start looking from this, aligned, address.

Thanks,
Alexey