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From: Jesper Dangaard Brouer <jbrouer@redhat.com> To: Yunsheng Lin <linyunsheng@huawei.com>, davem@davemloft.net, kuba@kernel.org Cc: brouer@redhat.com, alexander.duyck@gmail.com, linux@armlinux.org.uk, mw@semihalf.com, linuxarm@openeuler.org, yisen.zhuang@huawei.com, salil.mehta@huawei.com, thomas.petazzoni@bootlin.com, hawk@kernel.org, ilias.apalodimas@linaro.org, ast@kernel.org, daniel@iogearbox.net, john.fastabend@gmail.com, akpm@linux-foundation.org, peterz@infradead.org, will@kernel.org, willy@infradead.org, vbabka@suse.cz, fenghua.yu@intel.com, guro@fb.com, peterx@redhat.com, feng.tang@intel.com, jgg@ziepe.ca, mcroce@microsoft.com, hughd@google.com, jonathan.lemon@gmail.com, alobakin@pm.me, willemb@google.com, wenxu@ucloud.cn, cong.wang@bytedance.com, haokexin@gmail.com, nogikh@google.com, elver@google.com, yhs@fb.com, kpsingh@kernel.org, andrii@kernel.org, kafai@fb.com, songliubraving@fb.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, chenhao288@hisilicon.com Subject: Re: [PATCH net-next v2 2/4] page_pool: add interface to manipulate frag count in page pool Date: Thu, 12 Aug 2021 17:17:05 +0200 [thread overview] Message-ID: <d9bce937-1645-b209-a1d4-c7c0a6fcd1af@redhat.com> (raw) In-Reply-To: <1628217982-53533-3-git-send-email-linyunsheng@huawei.com> On 06/08/2021 04.46, Yunsheng Lin wrote: > +static inline long page_pool_atomic_sub_frag_count_return(struct page *page, > + long nr) > +{ > + long ret; > + > + /* As suggested by Alexander, atomic_long_read() may cover up the > + * reference count errors, so avoid calling atomic_long_read() in > + * the cases of freeing or draining the page_frags, where we would > + * not expect it to match or that are slowpath anyway. > + */ > + if (__builtin_constant_p(nr) && > + atomic_long_read(&page->pp_frag_count) == nr) > + return 0; > + > + ret = atomic_long_sub_return(nr, &page->pp_frag_count); > + WARN_ON(ret < 0); I worried about this WARN_ON() as it generates an 'ud2' instruction which influence I-cache fetching. But I have disassembled (objdump) the page_pool.o binary and the ud2 gets placed last in the main function page_pool_put_page() that use this inlined function. Thus, I assume this is not a problem :-) > + return ret;
next prev parent reply other threads:[~2021-08-12 15:17 UTC|newest] Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-08-06 2:46 [PATCH net-next v2 0/4] add frag page support in page pool Yunsheng Lin 2021-08-06 2:46 ` [PATCH net-next v2 1/4] page_pool: keep pp info as long as page pool owns the page Yunsheng Lin 2021-08-06 2:46 ` [PATCH net-next v2 2/4] page_pool: add interface to manipulate frag count in page pool Yunsheng Lin 2021-08-10 14:58 ` Jesper Dangaard Brouer 2021-08-11 0:48 ` Yunsheng Lin 2021-08-12 15:17 ` Jesper Dangaard Brouer [this message] 2021-08-06 2:46 ` [PATCH net-next v2 3/4] page_pool: add frag page recycling support " Yunsheng Lin 2021-08-06 2:46 ` [PATCH net-next v2 4/4] net: hns3: support skb's frag page recycling based on " Yunsheng Lin 2021-09-08 8:31 ` moyufeng 2021-09-08 15:08 ` Jakub Kicinski 2021-09-08 15:26 ` Ilias Apalodimas 2021-09-08 15:57 ` Jakub Kicinski 2021-09-08 16:47 ` Jesper Dangaard Brouer 2021-09-08 16:51 ` Ilias Apalodimas 2022-01-26 14:30 ` Jean-Philippe Brucker 2022-01-28 4:00 ` Yunsheng Lin 2022-01-28 9:21 ` Jean-Philippe Brucker 2022-01-29 8:44 ` Yunsheng Lin 2022-02-03 9:48 ` Jean-Philippe Brucker 2022-02-07 2:54 ` Yunsheng Lin 2022-03-24 18:09 ` Jean-Philippe Brucker 2021-08-10 14:01 ` [PATCH net-next v2 0/4] add frag page support in " Jakub Kicinski 2021-08-10 14:23 ` Jesper Dangaard Brouer 2021-08-10 14:43 ` Jakub Kicinski 2021-08-10 15:09 ` Alexander Duyck 2021-08-11 1:06 ` [Linuxarm] " Yunsheng Lin
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