From: Eric Dumazet <eric.dumazet@gmail.com>
To: Christoph Lameter <cl@linux.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Nick Piggin <npiggin@kernel.dk>,
Dave Chinner <david@fromorbit.com>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] percpu_counter : add percpu_counter_add_fast()
Date: Mon, 18 Oct 2010 17:39:40 +0200 [thread overview]
Message-ID: <1287416380.2409.13.camel@edumazet-laptop> (raw)
In-Reply-To: <alpine.DEB.2.00.1010181015290.755@router.home>
Le lundi 18 octobre 2010 à 10:24 -0500, Christoph Lameter a écrit :
> On Sat, 16 Oct 2010, Eric Dumazet wrote:
>
> > I based following patch against linux-2.6, I dont know if previous
> > Christoph patch is in a git tree. I'll respin it eventually.
>
> The prior patch was accepted by Andrew.
>
> > + * - It is preempt safe, but not IRQ safe (on UP)
>
> The IRQ safeness depends on the arch. this_cpu_add() in general only
> guarantees safety against preemption. It so happens that the x86
> implementation is irq safe as well.
>
> The IRQ safety for UP is therefore not an issue if you use this_cpu_add().
>
Nope, on UP, we dont use a per_cpu field, just a "s64 count".
struct percpu_counter {
s64 count;
};
> If you want to guarantee irqsafeness then use irqsafe_cpu_add() instead.
> It generates the same code on x86 for SMP but takes care of the UP issues.
>
> > +static inline void percpu_counter_add_fast(struct percpu_counter *fbc, long amount)
> > +{
> > + this_cpu_add(*fbc->counters, amount);
> > +}
>
> What happens in case of counter overflow?
>
Nothing special, as I stated the usuable width of such counters would be
restricted to a long, not an s64.
It should be enough to count "number of inodes, of sockets, ..."
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next prev parent reply other threads:[~2010-10-18 15:39 UTC|newest]
Thread overview: 111+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-29 12:18 [PATCH 0/17] fs: Inode cache scalability Dave Chinner
2010-09-29 12:18 ` [PATCH 01/17] kernel: add bl_list Dave Chinner
2010-09-30 4:52 ` Andrew Morton
2010-10-16 7:55 ` Nick Piggin
2010-10-16 16:28 ` Christoph Hellwig
2010-10-01 5:48 ` Christoph Hellwig
2010-09-29 12:18 ` [PATCH 02/17] fs: icache lock s_inodes list Dave Chinner
2010-10-01 5:49 ` Christoph Hellwig
2010-10-16 7:54 ` Nick Piggin
2010-10-16 16:12 ` Christoph Hellwig
2010-10-16 17:09 ` Nick Piggin
2010-10-17 0:42 ` Christoph Hellwig
2010-10-17 2:03 ` Nick Piggin
2010-09-29 12:18 ` [PATCH 03/17] fs: icache lock inode hash Dave Chinner
2010-09-30 4:52 ` Andrew Morton
2010-09-30 6:13 ` Dave Chinner
2010-10-01 6:06 ` Christoph Hellwig
2010-10-16 7:57 ` Nick Piggin
2010-09-29 12:18 ` [PATCH 04/17] fs: icache lock i_state Dave Chinner
2010-10-01 5:54 ` Christoph Hellwig
2010-10-16 7:54 ` Nick Piggin
2010-09-29 12:18 ` [PATCH 05/17] fs: icache lock i_count Dave Chinner
2010-09-30 4:52 ` Andrew Morton
2010-10-01 5:55 ` Christoph Hellwig
2010-10-01 6:04 ` Andrew Morton
2010-10-01 6:16 ` Christoph Hellwig
2010-10-01 6:23 ` Andrew Morton
2010-09-29 12:18 ` [PATCH 06/17] fs: icache lock lru/writeback lists Dave Chinner
2010-09-30 4:52 ` Andrew Morton
2010-09-30 6:16 ` Dave Chinner
2010-10-16 7:55 ` Nick Piggin
2010-10-01 6:01 ` Christoph Hellwig
2010-10-05 22:30 ` Dave Chinner
2010-09-29 12:18 ` [PATCH 07/17] fs: icache atomic inodes_stat Dave Chinner
2010-09-30 4:52 ` Andrew Morton
2010-09-30 6:20 ` Dave Chinner
2010-09-30 6:37 ` Andrew Morton
2010-10-16 7:56 ` Nick Piggin
2010-09-29 12:18 ` [PATCH 08/17] fs: icache protect inode state Dave Chinner
2010-10-01 6:02 ` Christoph Hellwig
2010-10-16 7:54 ` Nick Piggin
2010-09-29 12:18 ` [PATCH 09/17] fs: Make last_ino, iunique independent of inode_lock Dave Chinner
2010-09-30 4:53 ` Andrew Morton
2010-10-01 6:08 ` Christoph Hellwig
2010-10-16 7:54 ` Nick Piggin
2010-09-29 12:18 ` [PATCH 10/17] fs: icache remove inode_lock Dave Chinner
2010-09-29 12:18 ` [PATCH 11/17] fs: Factor inode hash operations into functions Dave Chinner
2010-10-01 6:06 ` Christoph Hellwig
2010-10-16 7:54 ` Nick Piggin
2010-09-29 12:18 ` [PATCH 12/17] fs: Introduce per-bucket inode hash locks Dave Chinner
2010-09-30 1:52 ` Christoph Hellwig
2010-09-30 2:43 ` Dave Chinner
2010-10-16 7:55 ` Nick Piggin
2010-09-29 12:18 ` [PATCH 13/17] fs: Implement lazy LRU updates for inodes Dave Chinner
2010-09-30 2:05 ` Christoph Hellwig
2010-10-16 7:54 ` Nick Piggin
2010-09-29 12:18 ` [PATCH 14/17] fs: Inode counters do not need to be atomic Dave Chinner
2010-09-29 12:18 ` [PATCH 15/17] fs: inode per-cpu last_ino allocator Dave Chinner
2010-09-30 2:07 ` Christoph Hellwig
2010-10-06 6:29 ` Dave Chinner
2010-10-06 8:51 ` Christoph Hellwig
2010-09-30 4:53 ` Andrew Morton
2010-09-30 5:36 ` Eric Dumazet
2010-09-30 7:53 ` Eric Dumazet
2010-09-30 8:14 ` Andrew Morton
2010-09-30 10:22 ` [PATCH] " Eric Dumazet
2010-09-30 16:45 ` Andrew Morton
2010-09-30 17:28 ` Eric Dumazet
2010-09-30 17:39 ` Andrew Morton
2010-09-30 18:05 ` Eric Dumazet
2010-10-01 6:12 ` Christoph Hellwig
2010-10-01 6:45 ` Eric Dumazet
2010-10-16 6:36 ` Nick Piggin
2010-10-16 6:40 ` Nick Piggin
2010-09-29 12:18 ` [PATCH 16/17] fs: Convert nr_inodes to a per-cpu counter Dave Chinner
2010-09-30 2:12 ` Christoph Hellwig
2010-09-30 4:53 ` Andrew Morton
2010-09-30 6:10 ` Dave Chinner
2010-10-16 7:55 ` Nick Piggin
2010-10-16 8:29 ` Eric Dumazet
2010-10-16 9:07 ` Andrew Morton
2010-10-16 9:31 ` Eric Dumazet
2010-10-16 14:19 ` [PATCH] percpu_counter : add percpu_counter_add_fast() Eric Dumazet
2010-10-18 15:24 ` Christoph Lameter
2010-10-18 15:39 ` Eric Dumazet [this message]
2010-10-18 16:12 ` Christoph Lameter
2010-10-21 22:37 ` Andrew Morton
2010-10-21 23:10 ` Christoph Lameter
2010-10-22 0:45 ` Andrew Morton
2010-10-22 1:55 ` Andrew Morton
2010-10-22 1:58 ` Nick Piggin
2010-10-22 2:14 ` Andrew Morton
2010-10-22 4:12 ` Eric Dumazet
2010-10-21 22:43 ` Andrew Morton
2010-10-21 22:58 ` Eric Dumazet
2010-10-21 23:18 ` Andrew Morton
2010-10-21 23:22 ` Eric Dumazet
2010-10-21 22:31 ` [PATCH 16/17] fs: Convert nr_inodes to a per-cpu counter Andrew Morton
2010-10-21 22:58 ` Eric Dumazet
2010-10-02 16:02 ` Christoph Hellwig
2010-09-29 12:18 ` [PATCH 17/17] fs: Clean up inode reference counting Dave Chinner
2010-09-30 2:15 ` Christoph Hellwig
2010-10-16 7:55 ` Nick Piggin
2010-10-16 16:14 ` Christoph Hellwig
2010-10-16 17:09 ` Nick Piggin
2010-09-30 4:53 ` Andrew Morton
2010-09-29 23:57 ` [PATCH 0/17] fs: Inode cache scalability Christoph Hellwig
2010-09-30 0:24 ` Dave Chinner
2010-09-30 2:21 ` Christoph Hellwig
2010-10-02 23:10 ` Carlos Carvalho
2010-10-04 7:22 ` Dave Chinner
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