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Message-ID: <e841d2f4-b221-9099-8312-6b859ccb98de@huawei.com> Date: Thu, 30 Nov 2023 17:00:52 +0800 From: Yunsheng Lin <linyunsheng@...wei.com> To: Alexander H Duyck <alexander.duyck@...il.com>, David Howells <dhowells@...hat.com>, <netdev@...r.kernel.org> CC: "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Willem de Bruijn <willemdebruijn.kernel@...il.com>, David Ahern <dsahern@...nel.org>, Matthew Wilcox <willy@...radead.org>, Jens Axboe <axboe@...nel.dk>, <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>, Jeroen de Borst <jeroendb@...gle.com>, Catherine Sullivan <csully@...gle.com>, Shailend Chand <shailend@...gle.com>, Felix Fietkau <nbd@....name>, John Crispin <john@...ozen.org>, Sean Wang <sean.wang@...iatek.com>, Mark Lee <Mark-MC.Lee@...iatek.com>, Lorenzo Bianconi <lorenzo@...nel.org>, Matthias Brugger <matthias.bgg@...il.com>, AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, Keith Busch <kbusch@...nel.org>, Jens Axboe <axboe@...com>, Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>, Chaitanya Kulkarni <kch@...dia.com>, Andrew Morton <akpm@...ux-foundation.org>, <linux-arm-kernel@...ts.infradead.org>, <linux-mediatek@...ts.infradead.org>, <linux-nvme@...ts.infradead.org> Subject: Re: [PATCH net-next 03/12] mm: Make the page_frag_cache allocator alignment param a pow-of-2 On 2023/5/27 23:54, Alexander H Duyck wrote: > On Wed, 2023-05-24 at 16:33 +0100, David Howells wrote: >> Make the page_frag_cache allocator's alignment parameter a power of 2 >> rather than a mask and give a warning if it isn't. >> >> This means that it's consistent with {napi,netdec}_alloc_frag_align() and >> allows __{napi,netdev}_alloc_frag_align() to be removed. I am trying to rmove the page frag implemetation in vhost_net_page_frag_refill() by using page_frag_alloc_align(), and I ended up having a simiar patch as this one. >> > > This goes against the original intention of these functions. One of the > reasons why this is being used is because when somebody enables > something like 2K jumbo frames they don't necessarily want to have to > allocate 4K SLABs. Instead they can just add a bit of overhead and get > almost twice the utilization out of an order 3 page. > > The requirement should only be cache alignment, not power of 2 > alignment. This isn't meant to be a slab allocator. We are just > sectioning up pages to handle mixed workloads. In the case of > networking we can end up getting everything from 60B packets, to 1514B > in the standard cases. That was why we started sectioning up pages in > the first place so putting a power of 2 requirement on it doens't fit > our use case at all and is what we were trying to get away from with > the SLAB allocators. It seems that is_power_of_2() checking in this patch does not excluding the non-align case if we are passing 'align' being 1, which means we still can support the 'everything from 60B packets, to 1514B' case. > > . >
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