lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Mon, 23 Jan 2017 15:27:16 +0900 From: Joonsoo Kim <iamjoonsoo.kim@....com> To: Sergey Senozhatsky <sergey.senozhatsky.work@...il.com> Cc: zhouxianrong <zhouxianrong@...wei.com>, linux-mm@...ck.org, linux-kernel@...r.kernel.org, akpm@...ux-foundation.org, sergey.senozhatsky@...il.com, minchan@...nel.org, ngupta@...are.org, Mi.Sophia.Wang@...wei.com, zhouxiyu@...wei.com, weidu.du@...wei.com, zhangshiming5@...wei.com, won.ho.park@...wei.com Subject: Re: [PATCH] mm: extend zero pages to same element pages for zram On Mon, Jan 23, 2017 at 01:03:47PM +0900, Sergey Senozhatsky wrote: > On (01/23/17 11:58), Joonsoo Kim wrote: > > Hello, > > > > On Sun, Jan 22, 2017 at 10:58:38AM +0800, zhouxianrong wrote: > > > 1. memset is just set a int value but i want to set a long value. > > > > Sorry for late review. > > > > Do we really need to set a long value? I cannot believe that > > long value is repeated in the page. Value repeatition is > > usually done by value 0 or 1 and it's enough to use int. And, I heard > > that value 0 or 1 is repeated in Android. Could you check the distribution > > of the value in the same page? > > Hello Joonsoo, > > thanks for taking a look and for bringing this question up. > so I kinda wanted to propose union of `ulong handle' with `uint element' > and switching to memset(), but I couldn't figure out if that change would > break detection of some patterns. > > /* Allocated for each disk page */ > struct zram_table_entry { > - unsigned long handle; > + union { > + unsigned long handle; > + unsigned int element; > + }; > unsigned long value; > }; Hello, Think about following case in 64 bits kernel. If value pattern in the page is like as following, we cannot detect the same page with 'unsigned int' element. AAAAAAAABBBBBBBBAAAAAAAABBBBBBBB... 4 bytes is 0xAAAAAAAA and next 4 bytes is 0xBBBBBBBB and so on. However, as I said before, I think that it is uncommon case. Thanks.
Powered by blists - more mailing lists