linux-kernel - Re: [PATCH v3 06/55] mm: Make the page_frag

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Date:   Wed, 5 Apr 2023 08:04:56 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     David Howells <dhowells@...hat.com>
Cc:     Matthew Wilcox <willy@...radead.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Christoph Hellwig <hch@...radead.org>,
        Jens Axboe <axboe@...nel.dk>, Jeff Layton <jlayton@...nel.org>,
        Christian Brauner <brauner@...nel.org>,
        Chuck Lever III <chuck.lever@...cle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        netdev@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Felix Fietkau <nbd@....name>, John Crispin <john@...ozen.org>,
        Sean Wang <sean.wang@...iatek.com>,
        Mark Lee <Mark-MC.Lee@...iatek.com>,
        Keith Busch <kbusch@...nel.org>,
        Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>,
        Chaitanya Kulkarni <kch@...dia.com>,
        linux-nvme@...ts.infradead.org, linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH v3 06/55] mm: Make the page_frag_cache allocator use
 per-cpu

On Fri, Mar 31, 2023 at 05:08:25PM +0100, David Howells wrote:
> Make the page_frag_cache allocator have a separate allocation bucket for
> each cpu to avoid racing.  This means that no lock is required, other than
> preempt disablement, to allocate from it, though if a softirq wants to
> access it, then softirq disablement will need to be added.

Can you split this into a separte series?  Right now I only see this
patch in mbox and miss the context on why wed want this.

> Make the NVMe and mediatek drivers pass in NULL to page_frag_cache() and
> use the default allocation buckets rather than defining their own.

Can you explain why?