Date: Wed, 10 Aug 2005 14:02:01 +0400 (MSD) From: Dmitry Morozovsky <marck@rinet.ru> To: freebsd-hackers@FreeBSD.org Subject: ffs_alloc.c: minfree Q Message-ID: <20050810135713.K18426@woozle.rinet.ru>
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Colleagues,
from ffs_alloc.c:
case FS_OPTSPACE:
/*
* Allocate an exact sized fragment. Although this makes
* best use of space, we will waste time relocating it if
* the file continues to grow. If the fragmentation is
* less than half of the minimum free reserve, we choose
* to begin optimizing for time.
*/
request = nsize;
if (fs->fs_minfree <= 5 ||
--->>> ~~~~~~~~~~~~~~~~~~~~~~
fs->fs_cstotal.cs_nffree >
(off_t)fs->fs_dsize * fs->fs_minfree / (2 * 100))
break;
log(LOG_NOTICE, "%s: optimization changed from SPACE to TIME\n",
fs->fs_fsmnt);
fs->fs_optim = FS_OPTTIME;
break;
For contemporary situation, where total size of file system can grow to
hundreds of Gs or even several Ts, 8% of space seems too high.
Maybe this algorithm should be slightly adjusted (I'm thinking of logarithmic
scale depending on file system size)?
Any (contemporary) references would be highly appreciated.
Sincerely,
D.Marck [DM5020, MCK-RIPE, DM3-RIPN]
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*** Dmitry Morozovsky --- D.Marck --- Wild Woozle --- marck@rinet.ru ***
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