From: 赵军奎 <bernard@vivo.com>
To: Christopher Lameter <cl@linux.com>
Cc: 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,
kernel@vivo.com
Subject: Re:Re: [PATCH] kmalloc_index optimization(add kmalloc max size check)
Date: Sat, 18 Apr 2020 09:32:54 +0800 (GMT+08:00) [thread overview]
Message-ID: <ALcAggApCIauiL91uBghEaoS.3.1587173574288.Hmail.bernard@vivo.com> (raw)
In-Reply-To: <alpine.DEB.2.21.2004171556170.29874@www.lameter.com>
From: Christopher Lameter <cl@linux.com>
Date: 2020-04-17 23:59:00
To: Bernard Zhao <bernard@vivo.com>
Cc: 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,kernel@vivo.com
Subject: Re: [PATCH] kmalloc_index optimization(add kmalloc max size check)>On Fri, 17 Apr 2020, Bernard Zhao wrote:
>
>> kmalloc size should never exceed KMALLOC_MAX_SIZE.
>> kmalloc_index realise if size is exceed KMALLOC_MAX_SIZE, e.g 64M,
>> kmalloc_index just return index 26, but never check with OS`s max
>> kmalloc config KMALLOC_MAX_SIZE. This index`s kmalloc caches maybe
>> not create in function create_kmalloc_caches.
>> We can throw an warninginfo in kmalloc at the beginning, instead of
>> being guaranteed by the buddy alloc behind.
>
>kmalloc_index(0 already bugs if the allocation is more than 64M
>
>
>...
>
> if (size <= 64 * 1024 * 1024) return 26;
> BUG();
>
>
>You could modify that to check for KMALLOC_MAX_SIZE with some more
>conditionals but then kmalloc_index) is written so that the compiler gets
>constant folding right.
>
>If you have a patch like that then please verify that all c compilers in
>use perform correct constant folding and do not add unnecessary code.
>
>
Sorry for the misunderstanding.
What I meant was that the “if”in kmalloc_index should be consistent
with KMALLOC_MAX_SIZE. For example, if the MAX_ZONEORDER configured
by the kernel is 11, which is 4M, then size >4M should trigger BUG(). If the
configuration is smaller, e.g MAX_ZONEORDER is 9, 1M, then the size > 1M
should be BUG.
But the current code is not, kmalloc_index will only be BUG() when it exceeds 64M.
next prev parent reply other threads:[~2020-04-18 1:33 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-17 7:09 [PATCH] kmalloc_index optimization(add kmalloc max size check) Bernard Zhao
2020-04-17 11:39 ` Michal Hocko
2020-04-17 12:17 ` 赵军奎
2020-04-17 13:42 ` Michal Hocko
2020-04-17 15:59 ` Christopher Lameter
2020-04-18 1:32 ` 赵军奎 [this message]
2020-04-19 16:42 ` Christopher Lameter
2020-04-21 2:53 ` 赵军奎
2020-04-21 15:57 ` Christopher Lameter
2020-04-21 14:15 ` Vlastimil Babka
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