linux-kernel - Re: semantics of rhashtable and sysvipc

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Message-ID: <CA+55aFzfEsC9op0UzYte7OaWnvv9Czqr-0owFo0FGDqPcfGiKQ@mail.gmail.com>
Date:   Thu, 24 May 2018 12:17:48 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Davidlohr Bueso <dave@...olabs.net>
Cc:     Thomas Graf <tgraf@...g.ch>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Manfred Spraul <manfred@...orfullife.com>,
        guillaume.knispel@...ersonicimagine.com,
        Linux API <linux-api@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: semantics of rhashtable and sysvipc

On Thu, May 24, 2018 at 12:08 PM Davidlohr Bueso <dave@...olabs.net> wrote:

> However, after how about the resize being based on HASH_MIN_SIZE instead
of
> HASH_DEFAULT_SIZE?

I think that sounds reasonable. We wouldn't expect this to ever happen in
practice, and as you say, if it *does* happen, the size of the hash array
is the last of our problems.

> Considering that some users set p.min_size to be rather large-ish (up to
1024
> buckets afaict), we'd need the following:

>          size = min(ht->p.min_size, HASH_MIN_SIZE);

Bah, let's just go for simplicity, and just make it HASH_MIN_SIZE
unconditionally, and just have a single fallback: if the first "normal"
allocation fails, do one single unconditional allocation with HASH_MIN_SIZE
and GFP_NOFAIL.

I think that should work fine.

                Linus