Date: Fri, 16 Oct 2015 13:16:39 -0600 From: Warner Losh <imp@bsdimp.com> To: Hans Petter Selasky <hp@selasky.org> Cc: Bruce Evans <brde@optusnet.com.au>, Warner Losh <imp@freebsd.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r289405 - head/sys/ufs/ffs Message-ID: <C670A059-B35F-41F3-907A-F0937320CA6D@bsdimp.com> In-Reply-To: <5620B15C.8090104@selasky.org> References: <201510160306.t9G3622O049128@repo.freebsd.org> <20151016151349.W1280@besplex.bde.org> <5620B15C.8090104@selasky.org>
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--Apple-Mail=_F5C7F81A-87C9-4B9F-AF3C-C309D07FE444 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=windows-1252 > On Oct 16, 2015, at 2:12 AM, Hans Petter Selasky <hp@selasky.org> = wrote: >=20 > On 10/16/15 08:21, Bruce Evans wrote: >> In addition, making the file contiguous in LBA space doesn't >> improve the access times from flash devices because they have no = seek >> time. >=20 > Hi, >=20 > This is not exactly true, like Bruce pointed out too. Maybe there = should be a check, that if the block is too small reallocate it, else = leave it for the sake of the flash. Doing 1K accesses versus 64K = accesses will typically show up in the performance benchmark regardless = of how fast the underlying medium is. But that=92s not what this does. It isn=92t the defrag code that takes = the 2-8k fragments and squashes them into 16-64k block size for the = device. This takes the larger blocks and makes sure they are next to = each other. This takes large contiguous space (like 2MB) and puts as = much as possible in a cylinder group. That=92s totally useless on a = flash drive. Since the sizes of the blocks are so large, moving them won=92t change = any benchmarks. Warner --Apple-Mail=_F5C7F81A-87C9-4B9F-AF3C-C309D07FE444 Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc Content-Description: Message signed with OpenPGP using GPGMail -----BEGIN PGP SIGNATURE----- Comment: GPGTools - https://gpgtools.org iQIcBAEBCgAGBQJWIU0XAAoJEGwc0Sh9sBEA2NAP/jExMKGTXDjVBkUPfavVpXSY cUdIspM7IEasio9YevjdT17MePqRGd5Iwc8ViYvZC2RwACUMYbjKl2fP02DxJfd2 BafqkQB+Ruxpgggj8YpV0J9o2vcagmehr9waX47DvlpQ+r1XnltmpK94xU3FP81F 4V2/7Cqqx0AA20yOD3dorEvZYEfV6w4fv1j0AqanXXzNOJ3uOY4G7XhTbDPr8eGg eOLeqocZ7ssN+Gms0VA8mUAK5nKld47bOJPM3M3+x3Q+GRxVQ0ojNQKHh8hBUlRN cLGL5SW0wTF4VpHAEx5MaC8YoWMhIvbFcf+rmFDTgfkeomE2eVSo5OdjbTQmdS/t yRGzjpRe/o20BSn0xURzkqwiIMKhoTzBeDOhyBP3WAmCy5P3JGsMCErsxTp3g0AM zEnA7d0AX79WfLxO+ybZyRFACO1W1N+0inlbB0QSouxIgqC85OJ2eohvQwexso1E MP+ZYpJXqiDsiEgt9r8Xy57yUbmS6Nyo5kkn6EutGozV+aQlZhgKaZtQl6KC7/1x fYvI4CFywfB/aVUQznaY3PGlDwd3123djNATTAI+z/dwX1P4R0elf2TfYlax0CBx aGY3PeExVZeclKD1eHYi/3ZlD37dzRs8Z7CZzd5OlXRHfvMZOMDi/lxswJZ2VcUh /UZAVvTW/OQ56aSejQhG =t5ja -----END PGP SIGNATURE----- --Apple-Mail=_F5C7F81A-87C9-4B9F-AF3C-C309D07FE444--
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