Date: Sun, 06 Jan 2008 17:12:59 +0000 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: Colin Percival <cperciva@freebsd.org> Cc: cvs-src@freebsd.org, src-committers@freebsd.org, cvs-all@freebsd.org Subject: Re: cvs commit: src/usr.sbin/gstat gstat.c Message-ID: <1767.1199639579@critter.freebsd.dk> In-Reply-To: Your message of "Sun, 06 Jan 2008 04:39:55 PST." <4780CC1B.8090708@freebsd.org>
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In message <4780CC1B.8090708@freebsd.org>, Colin Percival writes: >Poul-Henning Kamp wrote: >> When the ms/req fields exceed 1 second, drop the fractions to fit more digits. >> >> This is unfortunately necessary with some flash based devices which can >> get hundreds of seconds behind with softupdates enabled. > >I'm curious, why is this an issue with flash devices? Given their famous >ability to perform large numbers of transactions per second, I would have >expected flash-based drives to be the least likely to have this problem. The problem is flash-devices which are built (mostly) for cameras, their (cheap-ass) flash-adaptation-layer performs great for physically sequential writes for big files, and they fall totally apart with random writes to things like UFS/FFS inodes and bitmaps. Pretty much all of the layout optimizations in UFS/FFS are pessimizations for Flash devices. -- 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.
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