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  linux-cve-announce  PHC 
Open Source and information security mailing list archives
Hash Suite for Android: free password hash cracker in your pocket
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Sun, 05 Nov 2006 00:01:57 -0800
From:	Zachary Amsden <>
To:	Andi Kleen <>
Cc:	Linus Torvalds <>,
	Benjamin LaHaise <>,
	Chuck Ebbert <>,
	linux-kernel <>
Subject: Re: [rfc patch] i386: don't save eflags on task switch

Andi Kleen wrote:
>> For me, when compiled with -O2, it results in
>> 	84
>> 	88
>> 	132
>> which basically says: a "rdtsc->rdtsc" is 84 cycles, putting a "pushfl" in 
>> between is another _4_ cycles, and putting a "popfl" in between is about 
>> another 48 cycles. 
> This means we should definitely change restore_flags() to only STI, 
> never popf

sti is expensive as well; iirc just as expensive on most processors as 
popf, although I don't have hard numbers to back this up on hand.  An 
_unlikely_ jcc + popf? is better than a sti, for sure, but a likely 
jcc+popf could cost more than a jcc+sti, depending on model.

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