From mboxrd@z Thu Jan 1 00:00:00 1970 From: Al Viro Subject: Re: [PATCH v1 0/8] VFS: In-kernel copy system call Date: Sat, 5 Sep 2015 09:33:42 +0100 Message-ID: <20150905083342.GG22011@ZenIV.linux.org.uk> References: <1441397823-1203-1-git-send-email-Anna.Schumaker@Netapp.com> <4B41043F-5D85-42D6-8F20-2DCC45930EF4@dilger.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <4B41043F-5D85-42D6-8F20-2DCC45930EF4-m1MBpc4rdrD3fQ9qLvQP4Q@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Andreas Dilger Cc: Anna Schumaker , linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-btrfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, zab-ugsP4Wv/S6ZeoWH0uzbU5w@public.gmane.org, clm-b10kYP2dOMg@public.gmane.org, darrick.wong-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org, mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, andros-HgOvQuBEEgTQT0dZR+AlfA@public.gmane.org, hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org List-Id: linux-api@vger.kernel.org On Fri, Sep 04, 2015 at 04:25:27PM -0600, Andreas Dilger wrote: > This is a bit of a surprising result, since in my testing in the > past, copy_{to/from}_user() is a major consumer of CPU time (50% > of a CPU core at 1GB/s). What backing filesystem did you test on? While we are at it, was cp(1) using read(2)/write(2) loop or was it using something else (sendfile(2), for example)?