From: Rusty Russell <rusty@rustcorp.com.au>
To: Andrew Morton <akpm@digeo.com>
Cc: dipankar@in.ibm.com, linux-kernel@vger.kernel.org,
Bartlomiej Zolnierkiewicz <B.Zolnierkiewicz@elka.pw.edu.pl>,
paulus@samba.org
Subject: Re: [PATCH] kmalloc_percpu
Date: Wed, 07 May 2003 11:57:13 +1000 [thread overview]
Message-ID: <20030507023126.12F702C019@lists.samba.org> (raw)
In-Reply-To: Your message of "Tue, 06 May 2003 01:47:45 MST." <20030506014745.02508f0d.akpm@digeo.com>
In message <20030506014745.02508f0d.akpm@digeo.com> you write:
> Rusty Russell <rusty@rustcorp.com.au> wrote:
> >
> > It's a tradeoff, but I think it's worth it for a kmalloc_percpu which
> > is fast, space-efficient and numa-aware, since the code is needed
> > anyway.
>
> I don't beleive that kmalloc_percpu() itself needs to be fast, as you say.
>
> The code is _not_ NUMA-aware. Is it?
No, it's arch-overridable. You know me, I don't mess with
arch-specific stuff. 8)
> On 64GB 32-way that's 128MB of lowmem. Unpopular. I'd settle for a __setup
> thingy here, and a printk when the memory runs out.
Currently __setup is run far too late. Fortunately Bartlomiej has
been working on moving __setup earlier, for other reasons (two-stage
parameter parsing). In this case, it'd need to be before arch setup,
hmm...
> btw, what's wrong with leaving kmalloc_percpu() as-is, and only using this
> allocator for DEFINE_PERCPU()?
I figured that since the allocator is going to be there anyway, it
made sense to express kmalloc_percpu() in those terms. If you think
the price is too high, I can respect that.
The more people use the __per_cpu_offset instead of
smp_processor_id(), the cheaper it gets, even to the stage where some
archs might want to express smp_processor_id() in terms of
__per_cpu_offset, rather than vice-versa. Given that it's also more
space efficient (each var doesn't take one cacheline) too, I'd
recommend __alloc_percpu() of eg. single ints for long-lived objects
where I wouldn't recommend the current kmalloc_percpu().
Paul Mackerras points out that we could get the numa-aware allocation
plus "one big alloc" properties by playing with page mappings: reserve
1MB of virtual address, and map more pages as required. I didn't
think that we'd need that yet, though.
So, numerous options, and you're smarter than me, so you can decide 8)
Rusty.
--
Anyone who quotes me in their sig is an idiot. -- Rusty Russell.
next prev parent reply other threads:[~2003-05-07 2:18 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-05-05 8:08 [PATCH] kmalloc_percpu Rusty Russell
2003-05-05 8:47 ` Andrew Morton
2003-05-06 0:47 ` Rusty Russell
2003-05-06 1:52 ` Andrew Morton
2003-05-06 2:11 ` David S. Miller
2003-05-06 4:08 ` Rusty Russell
2003-05-06 3:40 ` David S. Miller
2003-05-06 5:02 ` Andrew Morton
2003-05-06 4:16 ` David S. Miller
2003-05-06 5:48 ` Andrew Morton
2003-05-06 5:35 ` David S. Miller
2003-05-06 6:55 ` Andrew Morton
2003-05-06 5:57 ` David S. Miller
2003-05-06 7:22 ` Andrew Morton
2003-05-06 6:15 ` David S. Miller
2003-05-06 7:34 ` Andrew Morton
2003-05-06 8:42 ` William Lee Irwin III
2003-05-06 14:38 ` Martin J. Bligh
2003-05-06 7:20 ` Dipankar Sarma
2003-05-06 8:28 ` Rusty Russell
2003-05-06 8:47 ` Andrew Morton
2003-05-07 1:57 ` Rusty Russell [this message]
2003-05-07 2:41 ` William Lee Irwin III
2003-05-07 4:03 ` Paul Mackerras
2003-05-07 4:22 ` William Lee Irwin III
2003-05-07 4:56 ` Paul Mackerras
2003-05-07 5:19 ` William Lee Irwin III
2003-05-07 4:10 ` Martin J. Bligh
2003-05-07 12:13 ` William Lee Irwin III
2003-05-07 4:15 ` Rusty Russell
2003-05-07 5:37 ` Andrew Morton
2003-05-08 0:53 ` Rusty Russell
2003-05-06 14:41 ` Martin J. Bligh
2003-05-06 6:42 ` Andrew Morton
2003-05-06 5:39 ` David S. Miller
2003-05-06 6:57 ` Andrew Morton
2003-05-06 7:25 ` Jens Axboe
2003-05-06 10:41 ` Ingo Oeser
2003-05-06 16:05 ` Bryan O'Sullivan
2003-05-06 8:06 ` Rusty Russell
2003-05-06 5:03 ` Dipankar Sarma
2003-05-06 4:28 ` Andrew Morton
2003-05-06 3:37 ` David S. Miller
2003-05-06 4:11 ` Rusty Russell
2003-05-06 5:07 ` Ravikiran G Thirumalai
2003-05-06 8:03 ` Rusty Russell
2003-05-06 9:23 ` David S. Miller
2003-05-06 9:34 ` Ravikiran G Thirumalai
2003-05-06 9:38 ` Dipankar Sarma
2003-05-07 2:14 ` Rusty Russell
2003-05-07 5:51 ` Ravikiran G Thirumalai
2003-05-07 6:16 ` Rusty Russell
2003-05-08 7:42 ` Ravikiran G Thirumalai
2003-05-08 7:47 ` Rusty Russell
-- strict thread matches above, loose matches on Subject: below --
2002-10-31 16:06 [patch] kmalloc_percpu Ravikiran G Thirumalai
2002-11-01 8:33 ` Rusty Russell
2002-11-05 16:00 ` Dipankar Sarma
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