linux-kernel - Re: [PATCH 2/4] lib/rhashtable: guarantee initial hashtable allocation

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Message-ID: <20180622065407.jqi3mvuzsj2jotbt@gondor.apana.org.au>
Date:   Fri, 22 Jun 2018 14:54:07 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Davidlohr Bueso <dave@...olabs.net>
Cc:     akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
        tgraf@...g.ch, manfred@...orfullife.com, mhocko@...nel.org,
        guillaume.knispel@...ersonicimagine.com, linux-api@...r.kernel.org,
        linux-kernel@...r.kernel.org, Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH 2/4] lib/rhashtable: guarantee initial hashtable
 allocation

On Thu, Jun 21, 2018 at 02:28:23PM -0700, Davidlohr Bueso wrote:
> rhashtable_init() may fail due to -ENOMEM, thus making the
> entire api unusable. This patch removes this scenario,
> however unlikely. In order to guarantee memory allocation,
> this patch always ends up doing GFP_KERNEL|__GFP_NOFAIL
> for both the tbl as well as alloc_bucket_spinlocks().
> 
> Upon the first table allocation failure, we shrink the
> size to the smallest value that makes sense and retry with
> __GFP_NOFAIL semantics. With the defaults, this means that
> from 64 buckets, we retry with only 4. Any later issues
> regarding performance due to collisions or larger table
> resizing (when more memory becomes available) is the least
> of our problems.
> 
> Signed-off-by: Davidlohr Bueso <dbueso@...e.de>

Acked-by: Herbert Xu <herbert@...dor.apana.org.au>

Thanks,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt