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Subject: Re: [PATCH RFC 1/8] dcache: show count of hash buckets in sysctl
 fs.dentry-state
To:     Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-mm@kvack.org, Alexander Viro <viro@zeniv.linux.org.uk>
References: <158893941613.200862.4094521350329937435.stgit@buzz>
 <158894059427.200862.341530589978120554.stgit@buzz>
From:   Waiman Long <longman@redhat.com>
Organization: Red Hat
Message-ID: <7c1cef87-2940-eb17-51d4-cbc40218b770@redhat.com>
Date:   Fri, 8 May 2020 10:49:42 -0400
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On 5/8/20 8:23 AM, Konstantin Khlebnikov wrote:
> Count of buckets is required for estimating average length of hash chains.
> Size of hash table depends on memory size and printed once at boot.
>
> Let's expose nr_buckets as sixth number in sysctl fs.dentry-state

The hash bucket count is a constant determined at boot time. Is there a 
need to use up one dentry_stat entry for that? Besides one can get it by 
looking up the kernel dmesg log like:

[    0.055212] Dentry cache hash table entries: 8388608 (order: 14, 
67108864 bytes)

Cheers,
Longman