Re:Re: Re: [PATCH V2] kmalloc_index optimization(code size & runtime stable)

[赵军奎 <bernard@vivo.com>]

发件人：Matthew Wilcox <willy@infradead.org>
发送日期：2020-04-21 22:36:09
收件人："赵军奎" <bernard@vivo.com>
抄送人：Christoph Lameter <cl@linux.com>,Pekka Enberg <penberg@kernel.org>,David Rientjes <rientjes@google.com>,Joonsoo Kim <iamjoonsoo.kim@lge.com>,Andrew Morton <akpm@linux-foundation.org>,linux-mm@kvack.org,linux-kernel@vger.kernel.org,opensource.kernel@vivo.com
主题：Re: Re: [PATCH V2] kmalloc_index optimization(code size & runtime stable)>On Tue, Apr 21, 2020 at 07:55:03PM +0800, 赵军奎 wrote:
>> Sure, i just received some kbuild compiler error mails and prompt me to do something? 
>> I don`t know why this happened, so i update the patch again.
>
>Don't.  The patch has been NACKed, so there's no need to post a v2.
>
>If you want to do something useful, how about looking at the effect
>of adding different slab sizes?  There's a fairly common pattern of
>allocating things which are a power of two + a header.  So it may make
>sense to have kmalloc caches of 320 (256 + 64), 576 (512 + 64) and 1088
>(1024 + 64).  I use 64 here as that's the size of a cacheline, so we
>won't get false sharing between users.
>
>This could save a fair quantity of memory; today if you allocate 512 +
>8 bytes, it will round up to 1024.  So we'll get 4 allocations per 4kB
>page, but with a 576-byte slab, we'd get 7 allocations per 4kB page.
>Of course, if there aren't a lot of users which allocate memory in this
>range, then it'll be a waste of memory.  On my laptop, it seems like
>there might be a decent amount of allocations in the right range:
>
>kmalloc-2k          3881   4384   2048   16    8 : tunables    0    0    0 : sla
>bdata    274    274      0
>kmalloc-1k          6488   7056   1024   16    4 : tunables    0    0    0 : slabdata    441    441      0
>kmalloc-512         7700   8256    512   16    2 : tunables    0    0    0 : slabdata    516    516      0
>
>Now, maybe 576 isn't quite the right size.  Need to try it on a variety
>of configurations and find out.  Want to investigate this?

This looks like a great idea!
Maybe I can do some research on our mobile phone products，
and see how the original size of kmalloc is distributed.
This may be useful as a reference to provide a flexible configuration method.
Thank you very much for your sharing.

Regards,
Bernard