From: David Howells <dhowells@redhat.com>
To: Alexander H Duyck <alexander.duyck@gmail.com>
Cc: dhowells@redhat.com, "David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
David Ahern <dsahern@kernel.org>,
Matthew Wilcox <willy@infradead.org>,
Jens Axboe <axboe@kernel.dk>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Jeroen de Borst <jeroendb@google.com>,
Catherine Sullivan <csully@google.com>,
Shailend Chand <shailend@google.com>,
Felix Fietkau <nbd@nbd.name>, John Crispin <john@phrozen.org>,
Sean Wang <sean.wang@mediatek.com>,
Mark Lee <Mark-MC.Lee@mediatek.com>,
Lorenzo Bianconi <lorenzo@kernel.org>,
Matthias Brugger <matthias.bgg@gmail.com>,
AngeloGioacchino Del Regno
<angelogioacchino.delregno@collabora.com>,
Keith Busch <kbusch@kernel.org>, Jens Axboe <axboe@fb.com>,
Christoph Hellwig <hch@lst.de>, Sagi Grimberg <sagi@grimberg.me>,
Chaitanya Kulkarni <kch@nvidia.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-arm-kernel@lists.infradead.org,
linux-mediatek@lists.infradead.org,
linux-nvme@lists.infradead.org
Subject: Re: [PATCH net-next 03/12] mm: Make the page_frag_cache allocator alignment param a pow-of-2
Date: Fri, 16 Jun 2023 16:28:29 +0100 [thread overview]
Message-ID: <617059.1686929309@warthog.procyon.org.uk> (raw)
In-Reply-To: <51161740e832334594960ed43430b868a6f892c3.camel@gmail.com>
Alexander H Duyck <alexander.duyck@gmail.com> wrote:
> The requirement should only be cache alignment, not power of 2
> alignment.
Sure, but, upstream, page_frag_alloc_align() allows the specification of an
alignment and applies that alignment by:
offset &= align_mask;
which doesn't really make sense unless the alignment boils down to being a
power of two. Now, it might make sense to kill off the align_mask parameter
and just go with SMP_CACHE_BYTES (which will be a power of two).
Note, though, that most users seem to use an align_mask of ~0u which feels a
bit dodgy (it's not an unsigned long), but is probably fine.
David
WARNING: multiple messages have this Message-ID (diff)
From: David Howells <dhowells@redhat.com>
To: Alexander H Duyck <alexander.duyck@gmail.com>
Cc: dhowells@redhat.com, "David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
David Ahern <dsahern@kernel.org>,
Matthew Wilcox <willy@infradead.org>,
Jens Axboe <axboe@kernel.dk>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Jeroen de Borst <jeroendb@google.com>,
Catherine Sullivan <csully@google.com>,
Shailend Chand <shailend@google.com>,
Felix Fietkau <nbd@nbd.name>, John Crispin <john@phrozen.org>,
Sean Wang <sean.wang@mediatek.com>,
Mark Lee <Mark-MC.Lee@mediatek.com>,
Lorenzo Bianconi <lorenzo@kernel.org>,
Matthias Brugger <matthias.bgg@gmail.com>,
AngeloGioacchino Del Regno
<angelogioacchino.delregno@collabora.com>,
Keith Busch <kbusch@kernel.org>, Jens Axboe <axboe@fb.com>,
Christoph Hellwig <hch@lst.de>, Sagi Grimberg <sagi@grimberg.me>,
Chaitanya Kulkarni <kch@nvidia.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-arm-kernel@lists.infradead.org,
linux-mediatek@lists.infradead.org,
linux-nvme@lists.infradead.org
Subject: Re: [PATCH net-next 03/12] mm: Make the page_frag_cache allocator alignment param a pow-of-2
Date: Fri, 16 Jun 2023 16:28:29 +0100 [thread overview]
Message-ID: <617059.1686929309@warthog.procyon.org.uk> (raw)
In-Reply-To: <51161740e832334594960ed43430b868a6f892c3.camel@gmail.com>
Alexander H Duyck <alexander.duyck@gmail.com> wrote:
> The requirement should only be cache alignment, not power of 2
> alignment.
Sure, but, upstream, page_frag_alloc_align() allows the specification of an
alignment and applies that alignment by:
offset &= align_mask;
which doesn't really make sense unless the alignment boils down to being a
power of two. Now, it might make sense to kill off the align_mask parameter
and just go with SMP_CACHE_BYTES (which will be a power of two).
Note, though, that most users seem to use an align_mask of ~0u which feels a
bit dodgy (it's not an unsigned long), but is probably fine.
David
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next prev parent reply other threads:[~2023-06-16 15:29 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-24 15:32 [PATCH net-next 00/12] splice, net: Replace sendpage with sendmsg(MSG_SPLICE_PAGES), part 3 David Howells
2023-05-24 15:33 ` [PATCH net-next 01/12] mm: Move the page fragment allocator from page_alloc.c into its own file David Howells
2023-05-24 15:33 ` [PATCH net-next 02/12] mm: Provide a page_frag_cache allocator cleanup function David Howells
2023-05-24 15:33 ` David Howells
2023-05-24 15:33 ` [PATCH net-next 03/12] mm: Make the page_frag_cache allocator alignment param a pow-of-2 David Howells
2023-05-24 15:33 ` David Howells
2023-05-27 15:54 ` Alexander H Duyck
2023-05-27 15:54 ` Alexander H Duyck
2023-11-30 9:00 ` Yunsheng Lin
2023-11-30 9:00 ` Yunsheng Lin
2023-06-16 15:28 ` David Howells [this message]
2023-06-16 15:28 ` David Howells
2023-06-16 16:06 ` Alexander Duyck
2023-06-16 16:06 ` Alexander Duyck
2023-05-24 15:33 ` [PATCH net-next 04/12] mm: Make the page_frag_cache allocator use multipage folios David Howells
2023-05-24 15:33 ` David Howells
2023-05-26 11:56 ` Yunsheng Lin
2023-05-26 11:56 ` Yunsheng Lin
2023-05-27 15:47 ` Alexander H Duyck
2023-05-27 15:47 ` Alexander H Duyck
2023-06-06 8:25 ` David Howells
2023-06-06 8:25 ` David Howells
2023-06-06 14:59 ` Alexander Duyck
2023-06-06 14:59 ` Alexander Duyck
2023-05-26 12:47 ` David Howells
2023-05-26 12:47 ` David Howells
2023-05-26 14:06 ` Mika Penttilä
2023-05-26 14:06 ` Mika Penttilä
2023-05-27 0:50 ` Jakub Kicinski
2023-05-27 0:50 ` Jakub Kicinski
2023-05-24 15:33 ` [PATCH net-next 05/12] mm: Make the page_frag_cache allocator handle __GFP_ZERO itself David Howells
2023-05-24 15:33 ` David Howells
2023-05-27 0:57 ` Jakub Kicinski
2023-05-27 0:57 ` Jakub Kicinski
2023-05-27 15:54 ` Alexander Duyck
2023-05-27 15:54 ` Alexander Duyck
2023-05-24 15:33 ` [PATCH net-next 06/12] mm: Make the page_frag_cache allocator use per-cpu David Howells
2023-05-24 15:33 ` David Howells
2023-05-27 1:02 ` Jakub Kicinski
2023-05-27 1:02 ` Jakub Kicinski
2023-05-24 15:33 ` [PATCH net-next 07/12] net: Clean up users of netdev_alloc_cache and napi_frag_cache David Howells
2023-05-24 15:33 ` [PATCH net-next 08/12] net: Copy slab data for sendmsg(MSG_SPLICE_PAGES) David Howells
2023-05-24 15:33 ` [PATCH net-next 09/12] tls/sw: Support MSG_SPLICE_PAGES David Howells
2023-05-27 1:08 ` Jakub Kicinski
2023-05-30 22:26 ` Bug in short splice to socket? David Howells
2023-05-31 0:32 ` Jakub Kicinski
2023-06-01 11:01 ` David Laight
2023-06-01 13:09 ` Linus Torvalds
2023-06-01 13:19 ` Linus Torvalds
2023-06-01 14:34 ` David Howells
2023-06-01 15:12 ` Linus Torvalds
2023-06-05 11:03 ` David Laight
2023-06-05 15:52 ` David Howells
2023-06-01 17:14 ` David Howells
2023-06-02 4:20 ` Jakub Kicinski
2023-06-02 8:23 ` David Howells
2023-06-02 11:28 ` Linus Torvalds
2023-06-02 11:44 ` David Howells
2023-06-02 12:11 ` Linus Torvalds
2023-06-02 16:39 ` Jakub Kicinski
2023-06-02 16:53 ` Linus Torvalds
2023-06-02 17:05 ` Linus Torvalds
2023-06-02 17:38 ` Jakub Kicinski
2023-06-02 20:38 ` David Howells
2023-06-02 20:50 ` David Howells
2023-05-24 15:33 ` [PATCH net-next 10/12] tls/sw: Convert tls_sw_sendpage() to use MSG_SPLICE_PAGES David Howells
2023-05-27 1:13 ` Jakub Kicinski
2023-05-24 15:33 ` [PATCH net-next 11/12] tls/device: Support MSG_SPLICE_PAGES David Howells
2023-05-24 15:33 ` [PATCH net-next 12/12] tls/device: Convert tls_device_sendpage() to use MSG_SPLICE_PAGES David Howells
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