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  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Sat, 7 Apr 2007 18:32:04 -0700 (PDT)
From:	Christoph Lameter <>
To:	Andrew Morton <>
cc:	Hugh Dickins <>, Nick Piggin <>,,
Subject: Re: [PATCH 2/2] Optimize compound_head() by avoiding a shared page

On Sat, 7 Apr 2007, Andrew Morton wrote:

> > I just tried the approach that we discussed earlier and it was not 
> > nice either.
> We've discussed at least three approaches, so we don't know to what you refer.

Thats the approach of checking two flags at the same time. In that case 
the compiler will generate and "and-immediate" and then a 
"compare-immediate" one branch but .... Yuck.

> Because I don't expect there will be much efficiency difference between the
> above and the use of another page flag.

Then we end up with all these small efficiency differences in all 
the code paths. I'd rather go for optimal performance in a frequently used 
construct like this.

This check is not rare. It is done on every SLAB free and on every 
get_page() and put_page(). Lets do the page flag.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

Powered by blists - more mailing lists