From: Matthew Wilcox <willy@infradead.org>
To: Pasha Tatashin <pasha.tatashin@oracle.com>
Cc: Andi Kleen <andi@firstfloor.org>,
linux-mm@kvack.org, sparclinux@vger.kernel.org
Subject: Re: [PATCH v2 1/3] sparc64: NG4 memset 32 bits overflow
Date: Wed, 1 Mar 2017 16:12:28 -0800 [thread overview]
Message-ID: <20170302001228.GL16328@bombadil.infradead.org> (raw)
In-Reply-To: <1e7db21b-808d-1f47-e78c-7d55c543ae39@oracle.com>
On Wed, Mar 01, 2017 at 04:20:28PM -0500, Pasha Tatashin wrote:
> Hi Andi,
>
> After thinking some more about this issue, I figured that I would not want
> to set default maximums.
>
> Currently, the defaults are scaled with system memory size, which seems like
> the right thing to do to me. They are set to size hash tables one entry per
> page and, if a scale argument is provided, scale them down to 1/2, 1/4, 1/8
> entry per page etc.
I disagree that it's the right thing to do. You want your dentry cache
to scale with the number of dentries in use. Scaling with memory size
is a reasonable approximation for smaller memory sizes, but allocating
8GB of *hash table entries* for dentries is plainly ridiculous, no matter
how much memory you have. You won't have half a billion dentries active
in most uses of such a large machine.
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next prev parent reply other threads:[~2017-03-02 0:12 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-01 0:14 [PATCH v2 0/3] Zeroing hash tables in allocator Pavel Tatashin
2017-03-01 0:14 ` [PATCH v2 1/3] sparc64: NG4 memset 32 bits overflow Pavel Tatashin
2017-03-01 0:24 ` Andi Kleen
2017-03-01 14:51 ` Pasha Tatashin
2017-03-01 15:19 ` Andi Kleen
2017-03-01 16:34 ` Pasha Tatashin
2017-03-01 17:31 ` Andi Kleen
2017-03-01 21:20 ` Pasha Tatashin
2017-03-01 23:10 ` Andi Kleen
2017-03-02 19:15 ` Pasha Tatashin
2017-03-02 0:12 ` Matthew Wilcox [this message]
2017-03-01 0:14 ` [PATCH v2 2/3] mm: Zeroing hash tables in allocator Pavel Tatashin
2017-03-01 0:14 ` [PATCH v2 3/3] mm: Updated callers to use HASH_ZERO flag Pavel Tatashin
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