From: NeilBrown <neilb@suse.de>
To: Dan Williams <djbw@fb.com>
Cc: Yuanhan Liu <yuanhan.liu@linux.intel.com>,
Fengguang Wu <fengguang.wu@intel.com>,
Li Shaohua <shli@fusionio.com>, "Theodore Ts'o" <tytso@mit.edu>,
Marti Raudsepp <marti@juffo.org>,
Kernel hackers <linux-kernel@vger.kernel.org>,
ext4 hackers <linux-ext4@vger.kernel.org>,
maze@google.com, "Shi, Alex" <alex.shi@intel.com>,
linux-fsdevel@vger.kernel.org,
linux RAID <linux-raid@vger.kernel.org>
Subject: Re: ext4 write performance regression in 3.6-rc1 on RAID0/5
Date: Thu, 23 Aug 2012 07:59:45 +1000 [thread overview]
Message-ID: <20120823075945.4dd02cbd@notabene.brown> (raw)
In-Reply-To: <CAA9_cmc4t_P3p-72iZx4UALNe3fupVqBKvvsvCtMH6G3HZUdww@mail.gmail.com>
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On Wed, 22 Aug 2012 13:47:07 -0700 Dan Williams <djbw@fb.com> wrote:
> On Tue, Aug 21, 2012 at 11:00 PM, NeilBrown <neilb@suse.de> wrote:
> > On Wed, 22 Aug 2012 11:57:02 +0800 Yuanhan Liu <yuanhan.liu@linux.intel.com>
> > wrote:
> >
> >>
> >> -#define NR_STRIPES 256
> >> +#define NR_STRIPES 1024
> >
> > Changing one magic number into another magic number might help your case, but
> > it not really a general solution.
> >
> > Possibly making sure that max_nr_stripes is at least some multiple of the
> > chunk size might make sense, but I wouldn't want to see a very large multiple.
> >
> > I thing the problems with RAID5 are deeper than that. Hopefully I'll figure
> > out exactly what the best fix is soon - I'm trying to look into it.
> >
> > I don't think the size of the cache is a big part of the solution. I think
> > correct scheduling of IO is the real answer.
>
> Not sure if this is what we are seeing here, but we still have the
> unresolved fast parity effect whereby slower parity calculation gives
> a larger time to coalesce writes. I saw this effect when playing with
> xor offload.
I did find a case where inserting a printk made it go faster again.
Replacing that with msleep(2) worked as well. :-)
I'm looking for a most robust solution though.
Thanks for the reminder.
NeilBrown
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next prev parent reply other threads:[~2012-08-22 22:00 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-15 18:33 NULL pointer dereference in ext4_ext_remove_space on 3.5.1 Marti Raudsepp
2012-08-16 2:46 ` Theodore Ts'o
2012-08-16 11:10 ` Fengguang Wu
2012-08-16 15:25 ` Theodore Ts'o
2012-08-16 20:21 ` Maciej Żenczykowski
2012-08-16 20:21 ` Maciej Żenczykowski
2012-08-16 21:19 ` Theodore Ts'o
2012-08-16 21:19 ` Theodore Ts'o
2012-08-16 21:40 ` Maciej Żenczykowski
2012-08-16 22:26 ` Theodore Ts'o
2012-08-16 22:44 ` Maciej Żenczykowski
2012-08-17 6:01 ` Fengguang Wu
2012-08-17 13:15 ` Theodore Ts'o
2012-08-17 13:22 ` Fengguang Wu
2012-08-17 13:50 ` [PATCH] ext4: fix kernel BUG on large-scale rm -rf commands Theodore Ts'o
2012-08-17 17:48 ` NULL pointer dereference in ext4_ext_remove_space on 3.5.1 Christoph Hellwig
2012-08-17 20:34 ` Theodore Ts'o
2012-08-17 20:34 ` Theodore Ts'o
2012-08-17 21:05 ` Christoph Hellwig
2012-08-17 21:05 ` Christoph Hellwig
2012-08-17 22:55 ` Dave Chinner
2012-08-17 22:55 ` Dave Chinner
2012-08-17 23:11 ` Theodore Ts'o
2012-08-17 23:11 ` Theodore Ts'o
2012-08-17 6:09 ` ext4 write performance regression in 3.6-rc1 Fengguang Wu
2012-08-17 13:40 ` Theodore Ts'o
2012-08-17 14:13 ` Fengguang Wu
2012-08-17 14:25 ` ext4 write performance regression in 3.6-rc1 on RAID0/5 Fengguang Wu
[not found] ` <20120817151318.GA2341@localhost>
2012-08-17 15:37 ` Theodore Ts'o
2012-08-17 20:44 ` NeilBrown
2012-08-21 9:42 ` Fengguang Wu
2012-08-21 12:07 ` Fengguang Wu
[not found] ` <20120822035702.GF2570@yliu-dev.sh.intel.com>
2012-08-22 4:07 ` Shaohua Li
2012-08-22 5:39 ` Yuanhan Liu
2012-08-22 6:00 ` NeilBrown
2012-08-22 6:31 ` Yuanhan Liu
2012-08-22 7:14 ` Andreas Dilger
2012-08-22 20:47 ` Dan Williams
2012-08-22 21:59 ` NeilBrown [this message]
2012-09-17 12:21 ` NULL pointer dereference in ext4_ext_remove_space on 3.5.1 Dmitry Monakhov
2012-09-17 13:52 ` Theodore Ts'o
2012-09-17 14:48 ` Dmitry Monakhov
2012-08-16 9:00 ` Fengguang Wu
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