From: Matthew Wilcox <willy@infradead.org>
To: 赵军奎 <bernard@vivo.com>
Cc: Christoph Lameter <cl@linux.com>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
opensource.kernel@vivo.com
Subject: Re: Re: [PATCH V2] kmalloc_index optimization(code size & runtime stable)
Date: Tue, 21 Apr 2020 07:36:09 -0700 [thread overview]
Message-ID: <20200421143609.GM5820@bombadil.infradead.org> (raw)
In-Reply-To: <AGEAdwClCFexXOQCGFZtCqqi.3.1587470103606.Hmail.bernard@vivo.com>
On Tue, Apr 21, 2020 at 07:55:03PM +0800, 赵军奎 wrote:
> Sure, i just received some kbuild compiler error mails and prompt me to do something?
> I don`t know why this happened, so i update the patch again.
Don't. The patch has been NACKed, so there's no need to post a v2.
If you want to do something useful, how about looking at the effect
of adding different slab sizes? There's a fairly common pattern of
allocating things which are a power of two + a header. So it may make
sense to have kmalloc caches of 320 (256 + 64), 576 (512 + 64) and 1088
(1024 + 64). I use 64 here as that's the size of a cacheline, so we
won't get false sharing between users.
This could save a fair quantity of memory; today if you allocate 512 +
8 bytes, it will round up to 1024. So we'll get 4 allocations per 4kB
page, but with a 576-byte slab, we'd get 7 allocations per 4kB page.
Of course, if there aren't a lot of users which allocate memory in this
range, then it'll be a waste of memory. On my laptop, it seems like
there might be a decent amount of allocations in the right range:
kmalloc-2k 3881 4384 2048 16 8 : tunables 0 0 0 : sla
bdata 274 274 0
kmalloc-1k 6488 7056 1024 16 4 : tunables 0 0 0 : slabdata 441 441 0
kmalloc-512 7700 8256 512 16 2 : tunables 0 0 0 : slabdata 516 516 0
Now, maybe 576 isn't quite the right size. Need to try it on a variety
of configurations and find out. Want to investigate this?
next prev parent reply other threads:[~2020-04-21 14:36 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-21 3:25 [PATCH V2] kmalloc_index optimization(code size & runtime stable) Bernard Zhao
2020-04-21 11:18 ` Matthew Wilcox
2020-04-21 11:55 ` 赵军奎
2020-04-21 14:36 ` Matthew Wilcox [this message]
2020-04-22 1:12 ` Re:Re: " 赵军奎
2020-04-21 13:13 ` Vlastimil Babka
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