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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1702467555; x=1703072355; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=p2HiWmQaWm4MP/NodEPVjpBx0ZdkVp5YIb/IjIDv1aQ=; b=MJNNUIiX4loDTiYDoKdtOZuc27WCCOIjsOqciojFI+PWG7oCYCKqX2rRnxYgY5fil7 4ac6S8K78zprO3ePYz8Dw/l753waMf1D1AMD+/hdsqj/3XBIk+Rp/dY1NKuz2ufvj0qc XmF74OEq8bP1IPRfmCFjZlYSQagkbyTCzi27l50GT84rnBWMOYXiR4Z+dE5PAkdVJhaa ODPmXZpDAar9DBK5sSGJPkVQGuj11u0feyGz4CdWWxZIg5N5G8eY6NUdqsaJ9B4JjjIb BdL2Rnszjour1zgBv3M2NcvV7EuyG414Ez7RqC7SgyC1G1dEF/T5nQNkuZjwPwV46TVt +xWg== X-Gm-Message-State: AOJu0YyANMffkMqY2uEKllOMBa8JkSy7RlJEtsiRwqni+kv8zNDOpXGY dTJkasbYyuXENzQqL994sYzfvy0/ZTnruXvShKSv0Q== X-Google-Smtp-Source: AGHT+IEczFWViTBtCu4945IpCG/4uQaaO2cIq/6WGJxtQAU45RYpbgodNpUAHz0opnj/+Zo60whYZ6Vkb/0qectBD9U= X-Received: by 2002:a19:5e53:0:b0:50c:c4c:2201 with SMTP id z19-20020a195e53000000b0050c0c4c2201mr3299603lfi.77.1702467555277; Wed, 13 Dec 2023 03:39:15 -0800 (PST) MIME-Version: 1.0 References: <20231212044614.42733-1-liangchen.linux@gmail.com> <20231212044614.42733-3-liangchen.linux@gmail.com> In-Reply-To: <20231212044614.42733-3-liangchen.linux@gmail.com> From: Ilias Apalodimas Date: Wed, 13 Dec 2023 13:38:38 +0200 Message-ID: Subject: Re: [PATCH net-next v9 2/4] page_pool: halve BIAS_MAX for multiple user references of a fragment To: Liang Chen Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, hawk@kernel.org, linyunsheng@huawei.com, netdev@vger.kernel.org, linux-mm@kvack.org, jasowang@redhat.com, almasrymina@google.com Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 23CED180027 X-Stat-Signature: 3de8apnuteaqht16pgqudofntbouw5st X-Rspam-User: X-HE-Tag: 1702467556-506090 X-HE-Meta: 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 yMr7msSA dVHvol6Ka50XuFYmfyy/C2OR+WjV279773/uSfMStlFiMJBdnzFE3dYZK/CmAcJtMCt1W+xMVMQMslbncwZrJ8FyUrKd0WYGGVSMlfgzDs/nnPfWw90PkkNMu8WbpZ34cRhK/iiwLcAjYSMPvw5z3A6NdMZ/G54eAKjZ7+4TMitIgAvLOHCEFrK0PYrLfJ+kvxV2ppI8PpZ4smxjZiAYliPF1gdOMfA+0xI90jWSdC2f93ETSHeZITMEAKYcUEk45u1dxZUWZQbU/vDRYu9YdOT0hVADWssehJPVvPotUxMAj+C7Ki3aoWaUZcZgQ1ophy5mUV5Ogr35s4C3x97MTFfTJ97p5kcWTbbT2t2ihX1jiOBAlLUJsuCLlPC142QpazFDYzFmV0jrGu+qyMiI2/zmGIQRks9kQZdInkfr0g28PxkWbIAGe7EgaSXjsBPSndy/H X-Bogosity: Ham, tests=bogofilter, spamicity=0.003473, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Liang, On Tue, 12 Dec 2023 at 06:47, Liang Chen wrote: > > Referring to patch [1], in order to support multiple users referencing the > same fragment and prevent overflow from pp_ref_count growing, the initial > value of pp_ref_count is halved, leaving room for pp_ref_count to increment > before the page is drained. > > [1] > https://lore.kernel.org/all/20211009093724.10539-3-linyunsheng@huawei.com/ We only need this if patch #4 is merged. In that case, I'd like to describe the changelog a bit better. Something along the lines of "Up to now, we were only subtracting from the number of used page fragments to figure out when a page could be freed or recycled. A following patch introduces support for multiple users referencing the same fragment. So reduce the initial page fragments value to half to avoid overflowing" Thanks /Ilias > same fragment > > Signed-off-by: Liang Chen > Reviewed-by: Yunsheng Lin > --- > net/core/page_pool.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/net/core/page_pool.c b/net/core/page_pool.c > index 106220b1f89c..436f7ffea7b4 100644 > --- a/net/core/page_pool.c > +++ b/net/core/page_pool.c > @@ -26,7 +26,7 @@ > #define DEFER_TIME (msecs_to_jiffies(1000)) > #define DEFER_WARN_INTERVAL (60 * HZ) > > -#define BIAS_MAX LONG_MAX > +#define BIAS_MAX (LONG_MAX >> 1) > > #ifdef CONFIG_PAGE_POOL_STATS > /* alloc_stat_inc is intended to be used in softirq context */ > -- > 2.31.1 >