| Date | Wed, 24 May 2006 22:01:35 +0800 | From | Limin Wang <> | Subject | Re: [PATCH 28/33] readahead: loop case |
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If the loopback files is bigger than the memory size, it may cause miss again and may better to turn on the read ahead?
Regards, Limin * Wu Fengguang <wfg@mail.ustc.edu.cn> [2006-05-24 19:13:14 +0800]:
> Disable look-ahead for loop file. > > Loopback files normally contain filesystems, in which case there are already > proper look-aheads in the upper layer, more look-aheads on the loopback file > only ruins the read-ahead hit rate. > > Signed-off-by: Wu Fengguang <wfg@mail.ustc.edu.cn> > --- > > I'd like to thank Tero Grundstr?m for uncovering the loopback problem. > > drivers/block/loop.c | 6 ++++++ > 1 files changed, 6 insertions(+) > > --- linux-2.6.17-rc4-mm3.orig/drivers/block/loop.c > +++ linux-2.6.17-rc4-mm3/drivers/block/loop.c > @@ -779,6 +779,12 @@ static int loop_set_fd(struct loop_devic > mapping = file->f_mapping; > inode = mapping->host; > > + /* > + * The upper layer should already do proper look-ahead, > + * one more look-ahead here only ruins the cache hit rate. > + */ > + file->f_ra.flags |= RA_FLAG_NO_LOOKAHEAD; > + > if (!(file->f_mode & FMODE_WRITE)) > lo_flags |= LO_FLAGS_READ_ONLY; > > > -- > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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