linux-kernel - Re: [PATCH] xfs: remove kmem_zalloc

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Message-ID: <20170307005420.GO17542@dastard>
Date:   Tue, 7 Mar 2017 11:54:20 +1100
From:   Dave Chinner <david@...morbit.com>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>
Cc:     Christoph Hellwig <hch@....de>, Brian Foster <bfoster@...hat.com>,
        Michal Hocko <mhocko@...nel.org>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Xiong Zhou <xzhou@...hat.com>, linux-xfs@...r.kernel.org,
        linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org, Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH] xfs: remove kmem_zalloc_greedy

On Mon, Mar 06, 2017 at 04:13:28PM -0800, Darrick J. Wong wrote:
> On Tue, Mar 07, 2017 at 01:07:54AM +0100, Christoph Hellwig wrote:
> > I like killing it, but shouldn't we just try a normal kmem_zalloc?
> > At least for the fallback it's the right thing, and even for an
> > order 2 allocation it seems like a useful first try.
> 
> I'm confused -- kmem_zalloc_large tries kmem_zalloc with KM_MAYFAIL and
> only falls back to __vmalloc if it doesn't get anything.

Yup, that's right.

> Or maybe I've misunderstood, and you're asking if we should try
> kmem_zalloc(4 pages), then kmem_zalloc(1 page), and only then switch to
> the __vmalloc calls?

Just call kmem_zalloc_large() for 4 pages without a fallback on
failure - that's exactly how we handle allocations for things like
the 64k xattr buffers....

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com