Date: Sun, 09 Mar 2003 08:57:59 +0100 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: Nate Lawson <nate@root.org> Cc: cvs-src@FreeBSD.org, src-committers@FreeBSD.org Subject: Re: cvs commit: src/sys/sys devicestat.h Message-ID: <78207.1047196679@critter.freebsd.dk> In-Reply-To: Your message of "Sat, 08 Mar 2003 23:50:06 PST." <Pine.BSF.4.21.0303082347200.90870-100000@root.org>
next in thread | previous in thread | raw e-mail | index | archive | help
In message <Pine.BSF.4.21.0303082347200.90870-100000@root.org>, Nate Lawson wri tes: >> Yes, these structures will be mmap'ed from kernel to userland and user >> land will (likely) memcpy() them to private storage as snapshot'ing. >> To be able to tell if you have an atomic snapshot, the two counters >> must be identical. > >How about a mtx covering the structure and a read from the device returns >the structure under lock? The goal is to avoid locking in the kernel and put the overhead in userland. Remember, most of the time nobody cares about the statistics so they should be cheap. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-src" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?78207.1047196679>