linux-kernel - Re: [PATCH v2 3/3] vfs: Enable list batching for the superblock's inode list

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 linux-cve-announce 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]

Message-ID: <56AFD649.9030707@hpe.com>
Date:	Mon, 01 Feb 2016 17:03:53 -0500
From:	Waiman Long <waiman.long@....com>
To:	Andi Kleen <andi@...stfloor.org>
CC:	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org, x86@...nel.org,
	linux-kernel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Scott J Norton <scott.norton@...com>,
	Douglas Hatch <doug.hatch@...com>
Subject: Re: [PATCH v2 3/3] vfs: Enable list batching for the superblock's
 inode list

On 02/01/2016 12:45 PM, Andi Kleen wrote:
>> I'm wondering, why are inode_sb_list_add()/del() even called for a presumably
>> reasonably well cached benchmark running on a system with enough RAM? Are these
>> perhaps thousands of temporary files, already deleted, and released when all the
>> file descriptors are closed as part of sys_exit()?
>>
>> If that's the case then I suspect an even bigger win would be not just to batch
>> the (sb-)global list fiddling, but to potentially turn the sb list into a
>> percpu_alloc() managed set of per CPU lists? It's a bigger change, but it could
> We had such a patch in the lock elision patchkit (It avoided a lot
> of cache line bouncing leading to aborts)
>
> https://git.kernel.org/cgit/linux/kernel/git/ak/linux-misc.git/commit/?h=hle315/combined&id=f1cf9e715a40f44086662ae3b29f123cf059cbf4
>
> -Andi
>
>

I like your patch though it cannot be applied cleanly for the current 
upstream kernel. I will port it to the current kernel and run my 
microbenchmark to see what performance gain I can get.

Cheers,
Longman