From: Andrew Morton <akpm@linux-foundation.org>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Dave Chinner <david@fromorbit.com>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] fs: inode per-cpu last_ino allocator
Date: Thu, 30 Sep 2010 09:45:58 -0700 [thread overview]
Message-ID: <20100930094558.97c9afa2.akpm@linux-foundation.org> (raw)
In-Reply-To: <1285842136.2615.251.camel@edumazet-laptop>
On Thu, 30 Sep 2010 12:22:16 +0200 Eric Dumazet <eric.dumazet@gmail.com> wrote:
> Le jeudi 30 septembre 2010 __ 01:14 -0700, Andrew Morton a __crit :
>
> > Perhaps
> >
> > WARN_ON_ONCE(preemptible());
> >
> > if we had a developer-only version of WARN_ON_ONCE, which we don't.
>
> Or just use a regular PER_CPU variable, even on !SMP, and get preempt
> safe implementation.
Good stuff.
> What do you think of following patch, on top of current linux-2.6 tree ?
>
> ...
>
> +static noinline unsigned int last_ino_get(void)
> +{
> + unsigned int *p = &get_cpu_var(last_ino);
> + unsigned int res = *p;
> +
> +#ifdef CONFIG_SMP
> + if (unlikely((res & (LAST_INO_BATCH - 1)) == 0)) {
> + static atomic_t shared_last_ino;
> + int next = atomic_add_return(LAST_INO_BATCH, &shared_last_ino);
> +
> + res = next - LAST_INO_BATCH;
> + }
> +#endif
> + *p = ++res;
> + put_cpu_var(last_ino);
> + return res;
> +}
Could eliminate `p' I guess, but that would involve using
__get_cpu_var() as an lval, which looks vile and might generate worse
code.
Readers of this code won't know why last_ino_get() was marked noinline.
It looks wrong, really.
next prev parent reply other threads:[~2010-09-30 16:45 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 [this message]
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
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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