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From: Neil Brown <neilb@suse.de>
To: Sage Weil <sage@newdream.net>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>, Greg KH <greg@kroah.com>,
	linux-next@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: linux-next: build failure after merge of the driver-core tree
Date: Wed, 24 Mar 2010 12:37:23 +1100	[thread overview]
Message-ID: <20100324123723.43d24a42@notabene.brown> (raw)
In-Reply-To: <Pine.LNX.4.64.1003170847110.25675@cobra.newdream.net>

On Wed, 17 Mar 2010 08:51:49 -0700 (PDT)
Sage Weil <sage@newdream.net> wrote:


> > It is a pity that this code cannot use mempool_t....
> > What if mempool_t were changed to only re-alloc the vector of pointers when
> > it grew, or when it shrank to less than 1/2 it's current size.  Would that
> > reduce the frequency of allocations enough for you to be comfortable with it? 
> > i.e. always make the vector a power-of-2 size (which is what is probably
> > allocated anyway) while the pool size might be less.
> > ??
> 
> That would improve the situation, but still mean potentially large 
> allocations (the pools can grow pretty big) that aren't strictly 
> necessary.  I can imagine a more modular mempool_t with an ops vector for 
> adding/removing from the pool to cope with situations like this, but I'm 
> not sure it's worth the effort?

How big?
mempools (and equivalents) should just be large enough to get you through a
tight spot.  The working assumption is that they will not normally be used.
So 2 or 3 should normally be plenty.

(looks at code)

The only time you resize a ceph_mempool is in ceph_monc_do_statfs
where you increment it, perform a synchronous statfs call on the 
network, then decrement the size of the mempool.
How many concurrent statfs calls does it even make sense to make.
I'm probably missing something obvious, but wouldn't it make sense to
put that all under a mutex so there was only ever one outstanding statfs (per
filesystem) - or maybe under a counting semaphore to allow some small number,
and make sure to prime the mempool to cover that number.
Then you would never resize a mempool at all.

I notice that all other mempools that ceph uses are sensibly quite small and
stay that way.

NeilBrown

  parent reply	other threads:[~2010-03-24  1:37 UTC|newest]

Thread overview: 181+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-03-17  4:41 linux-next: build failure after merge of the driver-core tree Stephen Rothwell
2010-03-17  7:21 ` Neil Brown
2010-03-17 15:51   ` Sage Weil
2010-03-17 22:30     ` Stephen Rothwell
2010-03-24  1:37     ` Neil Brown [this message]
2010-03-24 14:54       ` Sage Weil
  -- strict thread matches above, loose matches on Subject: below --
2023-08-15  7:24 Stephen Rothwell
2023-08-15 15:21 ` Greg KH
2023-08-16  7:39   ` Maxime Ripard
2023-04-11  4:38 Stephen Rothwell
2023-04-11  9:55 ` Daniel Vetter
2023-04-11 10:40   ` Greg KH
2023-04-11 15:01     ` Daniel Vetter
2023-04-11 15:08       ` Jeffrey Hugo
2023-04-11 15:13         ` Greg KH
2023-04-11 15:26           ` Jeffrey Hugo
2023-04-11 15:29             ` Jeffrey Hugo
2023-04-11 16:31               ` Daniel Vetter
2023-04-11 17:18                 ` Jeffrey Hugo
2023-04-11 18:21                   ` Daniel Vetter
2023-04-11 18:37                     ` Jeffrey Hugo
2023-04-11 18:47                       ` Daniel Vetter
2023-04-12  6:11                         ` Greg KH
2023-03-27  4:46 Stephen Rothwell
2023-03-27  7:33 ` Greg KH
2023-03-27  8:22   ` Stephen Rothwell
2023-03-27  9:15     ` Greg KH
2023-03-27 15:09       ` Vasily Gorbik
2023-01-30  4:28 Stephen Rothwell
2023-01-30 16:01 ` Greg KH
2023-01-30 16:23   ` Geert Uytterhoeven
2022-12-01  2:18 Stephen Rothwell
2022-11-30  1:38 Stephen Rothwell
2022-11-30 12:01 ` Greg KH
2022-11-28  2:36 Stephen Rothwell
2022-11-28 11:50 ` Greg KH
2022-11-28 12:44   ` Stephen Rothwell
2022-11-28 16:22     ` Greg KH
2022-11-28 19:46       ` Stephen Rothwell
2022-11-29  8:28         ` Greg KH
2022-11-28 17:35     ` Greg KH
2022-11-14  4:12 Stephen Rothwell
2022-11-14  8:46 ` Andy Shevchenko
2022-11-14  8:59   ` Greg KH
2021-07-23  5:09 Stephen Rothwell
2021-07-23  5:34 ` Uwe Kleine-König
2021-08-10 12:13   ` Geert Uytterhoeven
2021-08-12 20:51     ` Doug Anderson
2021-02-10 10:47 Stephen Rothwell
2021-02-10 18:18 ` Greg KH
2021-02-10 19:06   ` Saravana Kannan
2021-02-10 19:17     ` Saravana Kannan
2021-02-10 19:36       ` Greg KH
2021-02-10 20:14       ` Rob Herring
2021-02-10 20:43         ` Saravana Kannan
2021-02-10 20:59           ` Rob Herring
2020-09-09  5:47 Stephen Rothwell
2020-09-09  7:21 ` Greg KH
2020-09-09 21:47   ` Kees Cook
2020-09-09  7:28 ` Greg KH
2020-07-27  6:55 Stephen Rothwell
2020-07-27 10:17 ` Greg KH
2020-07-28 19:53   ` Kees Cook
2019-09-18 17:09 Mark Brown
2019-09-18 18:52 ` Greg KH
2019-09-18 19:03   ` Linus Torvalds
2019-09-18 19:07     ` Greg KH
2019-09-18 20:56       ` Suzuki K Poulose
2019-09-18 21:55     ` Mark Brown
2019-08-29  7:35 Stephen Rothwell
2019-08-29 10:10 ` Greg KH
2019-02-01  2:41 Stephen Rothwell
2019-02-01 14:18 ` Greg KH
2017-06-13  6:04 Stephen Rothwell
2017-06-13  6:20 ` Greg KH
2017-06-13  6:25   ` Stephen Rothwell
2017-06-13  6:30   ` Sergey Senozhatsky
2016-05-02  5:42 Stephen Rothwell
2016-05-02 11:40 ` William Breathitt Gray
2016-05-02 14:47   ` Greg KH
2015-05-21  7:52 Stephen Rothwell
2014-12-01  7:49 Stephen Rothwell
2014-05-28  8:03 Stephen Rothwell
2014-05-28  9:30 ` Jean Delvare
2014-03-12  0:51 Mark Brown
2014-03-12  1:50 ` Greg KH
2014-03-12  3:55   ` Benjamin Herrenschmidt
2014-03-12 11:37     ` Mark Brown
2014-03-12 19:59       ` Benjamin Herrenschmidt
2014-03-12 20:02         ` Tejun Heo
2014-03-12 20:14           ` Benjamin Herrenschmidt
2014-03-12 20:21             ` Tejun Heo
2014-03-13  0:37               ` Benjamin Herrenschmidt
2014-03-13 22:14                 ` Benjamin Herrenschmidt
2014-03-14 13:00                   ` Tejun Heo
2014-03-15  0:03                   ` Greg KH
2014-03-15  2:57                     ` Benjamin Herrenschmidt
2014-03-15  5:29                       ` Greg KH
2014-03-15  7:14                         ` Benjamin Herrenschmidt
2014-03-16 23:16                         ` Stephen Rothwell
2014-03-17 18:36                           ` Greg KH
2014-03-16 23:16   ` Stephen Rothwell
2014-03-17 18:33     ` Greg KH
2014-03-17 20:33       ` Benjamin Herrenschmidt
2014-03-17 21:56         ` Greg KH
2014-03-17 22:05           ` Tejun Heo
2014-03-17 22:21             ` Tejun Heo
2014-03-18  0:07               ` Stewart Smith
2014-03-18  0:22               ` Benjamin Herrenschmidt
2014-03-18 15:58                 ` Tejun Heo
2014-03-18  0:00           ` Stewart Smith
2014-03-18  0:16           ` Benjamin Herrenschmidt
2014-03-17  8:28 ` Stephen Rothwell
2013-08-22  5:39 Stephen Rothwell
2013-08-22 15:36 ` Greg KH
2013-01-18  2:29 Stephen Rothwell
2013-01-18  4:13 ` Greg KH
2013-01-18 14:14   ` Kondratiev, Vladimir
2012-08-17  4:01 Stephen Rothwell
2012-08-17 13:25 ` Greg KH
2012-07-10  5:32 Stephen Rothwell
2012-07-10  9:03 ` Mark Brown
2012-07-10 11:14   ` Stephen Rothwell
2012-07-10 21:10     ` Linus Walleij
2012-05-01  4:59 Stephen Rothwell
2012-05-01  7:05 ` Bart Van Assche
2012-05-01 13:45 ` Greg KH
2012-04-19  4:48 Stephen Rothwell
2012-04-19 20:07 ` Greg KH
2012-04-20  2:19 ` Greg KH
2012-01-27  2:59 Stephen Rothwell
2012-01-27 15:24 ` Alan Stern
2012-01-27 22:36 ` Greg KH
2012-01-05  6:28 Stephen Rothwell
2012-01-05 23:20 ` Greg KH
2011-12-28  6:45 Stephen Rothwell
2012-01-03 16:21 ` Greg KH
2012-01-04  0:07   ` Kay Sievers
2012-01-04  0:31     ` Greg KH
2012-01-04 22:03       ` Kay Sievers
2012-01-04 23:13         ` Greg KH
2012-01-04 23:07 ` Greg KH
2012-01-04 23:48   ` Stephen Rothwell
2012-01-05  0:01     ` Kay Sievers
2012-01-05  0:17       ` Stephen Rothwell
2012-01-05  0:57       ` Josh Triplett
2011-12-15  6:37 Stephen Rothwell
2011-12-15  7:21 ` Greg KH
2011-12-15 10:10   ` Kay Sievers
2011-12-15 19:09     ` Greg KH
2011-12-14  4:48 Stephen Rothwell
2011-12-14  9:24 ` Peter Zijlstra
2011-12-14 15:03   ` Greg KH
2011-12-14 15:13     ` Peter Zijlstra
2011-12-14 17:01       ` Greg KH
2011-12-14 19:24         ` Greg KH
2011-11-21  1:57 Stephen Rothwell
2010-08-04  4:25 Stephen Rothwell
2010-08-04  4:44 ` Guenter Roeck
2010-08-04 15:52 ` Greg KH
2010-08-04 21:24 ` Jesse Barnes
2010-05-18  6:45 Stephen Rothwell
2010-05-18  7:00 ` Eric W. Biederman
2010-05-18  7:48   ` Al Viro
2010-05-18  7:54   ` Stephen Rothwell
2010-05-18 10:35     ` Eric W. Biederman
2010-05-18 15:02       ` Al Viro
2010-05-18 19:58 ` Eric W. Biederman
2010-05-18 21:25   ` Greg KH
2010-05-18 21:59     ` Eric W. Biederman
2010-05-18  6:44 Stephen Rothwell
2010-05-18 14:02 ` Greg KH
2010-05-18 14:04   ` Chris Wright
2010-05-18 21:06   ` Chris Wright
2010-05-18 21:24     ` Greg KH
2010-03-03  6:14 Stephen Rothwell
2010-03-03  6:31 ` Stephen Rothwell
2010-02-16  6:39 Stephen Rothwell
2010-02-16  9:01 ` Jean Delvare
2010-02-17  4:56   ` Greg KH
2010-02-18  4:27     ` Greg KH

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