linux-kernel - Re: [lkp-robot] [fs] 3deb642f0d: will-it-scale.per_process

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: <20180622120739.GA15351@lst.de>
Date:   Fri, 22 Jun 2018 14:07:39 +0200
From:   Christoph Hellwig <hch@....de>
To:     Al Viro <viro@...IV.linux.org.uk>
Cc:     Christoph Hellwig <hch@....de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        kernel test robot <xiaolong.ye@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        LKP <lkp@...org>
Subject: Re: [lkp-robot] [fs] 3deb642f0d: will-it-scale.per_process_ops
        -8.8% regression

On Fri, Jun 22, 2018 at 12:56:13PM +0100, Al Viro wrote:
> 	So mark that in ->f_mode - I strongly suspect that
> sk_can_busy_loop(sock->sk) can't change while an opened file is there.
> And lift that (conditional on new FMODE_BUSY_LOOP) into do_poll()
> and do_select() - we *already* have bits of pieces of that logics in
> there and that way they'd at least be gathered in one place.

The problem is that call to sk_busy_loop(), which is going to be indirect
no matter what.

> 
> 	Then replace ->get_poll_head() with file->f_poll_head and
> see what it gives.

Working on it right now.  Works so far except for the busy loop case.
I'm looking into a separate methods just for that as a first idea.