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
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Date:	Wed, 22 Oct 2014 21:43:08 -0500
From:	Alex Thorlton <>
Cc:	Andrew Morton <>,
	Bob Liu <>,
	David Rientjes <>,
	"Eric W. Biederman" <>,
	Hugh Dickins <>,
	Ingo Molnar <>,
	Kees Cook <>,
	"Kirill A. Shutemov" <>,
	Mel Gorman <>, Oleg Nesterov <>,
	Peter Zijlstra <>,
	Rik van Riel <>,
	Thomas Gleixner <>,
	Vladimir Davydov <>,
Subject: Re: [PATCH 0/4] Convert khugepaged to a task_work function

Please ignore!  Screwed up my git send-email...  Sending the proper
version here in a bit...

On Wed, Oct 22, 2014 at 09:35:02PM -0500, Alex Thorlton wrote:
> Hey everyone,
> Last week, while discussing possible fixes for some unexpected/unwanted behavior
> from khugepaged (see: several people
> mentioned possibly changing changing khugepaged to work as a task_work function
> instead of a kernel thread.  This will give us finer grained control over the
> page collapse scans, eliminate some unnecessary scans since tasks that are
> relatively inactive will not be scanned often, and eliminate the unwanted
> behavior described in the email thread I mentioned.
> This initial patch is fully functional, but there are quite a few areas that
> will need to be polished up before it's ready to be considered for a merge.  I
> wanted to get this initial version out with some basic test results quickly, so
> that people can give their opinions and let me know if there's anything they'd
> like to see done differently (and there probably is :).  I'll give details on
> the code in the individual patches.
> I gathered some pretty rudimentary test data using a 48-thread NAMD simulation
> pinned to a cpuset with 8 cpus and about 60g of memory.  I'm checking to see if
> I'm allowed to publish the input data so that others can replicate the test.  In
> the meantime, if somebody knows of a publicly available benchmark that stresses
> khugepaged, that would be helpful.
> The only data point I gathered was the number of pages collapsed, sampled every
> ten seconds, for the lifetime of the job.  This one statistic gives a pretty
> decent illustration of the difference in behavior between the two kernels, but I
> intend to add some other counters to measure fully completed scans, failed
> allocations, and possibly scans skipped due to timer constraints.
> The data for the standard kernel (with a very small patch to add the stat
> counter that I used to the task_struct) is available here:
> This was a fairly recent kernel (last Tuesday).  Commit ID:
> 2d65a9f48fcdf7866aab6457bc707ca233e0c791.  I'll send the patches I used for that
> kernel as a reply to this message shortly.
> The output from the modified kernel is stored here:
> The output is stored in a pretty dumb format (*really* wide).  Best viewed in a
> simple text editor with word wrap off, just fyi.
> Quick summary of what I found:  Both kernels performed about the same when it
> comes to overall runtime, my kernel was 22 seconds faster with a total runtime
> of 4:13:07.  Not a significant difference, but important to note that there was
> no apparent performance degradation.  The most interesting result is that my
> kernel completed the majority of the necessary page collapses for this job in
> 2:04, whereas the mainline kernel took 29:05 to get to the same point.
> Let me know what you think.  Any suggestions are appreciated!
> - Alex
> Cc: Andrew Morton <>
> Cc: Bob Liu <>
> Cc: David Rientjes <>
> Cc: Eric W. Biederman <>
> Cc: Hugh Dickins <>
> Cc: Ingo Molnar <>
> Cc: Kees Cook <>
> Cc: Kirill A. Shutemov <>
> Cc: Mel Gorman <>
> Cc: Oleg Nesterov <>
> Cc: Peter Zijlstra <>
> Cc: Rik van Riel <>
> Cc: Thomas Gleixner <>
> Cc: Vladimir Davydov <>
> Cc:
> Alex Thorlton (4):
>   Disable khugepaged thread
>   Add pgcollapse controls to task_struct
>   Convert khugepaged scan functions to work with task_work
>   Add /proc files to expose per-mm pgcollapse stats
>  fs/proc/base.c             |  23 +++++++
>  include/linux/khugepaged.h |  10 ++-
>  include/linux/sched.h      |  16 +++++
>  kernel/fork.c              |   7 ++
>  kernel/sched/fair.c        |  18 +++++
>  mm/huge_memory.c           | 162 +++++++++++++++------------------------------
>  6 files changed, 123 insertions(+), 113 deletions(-)
> -- 
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