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Wed, 13 Dec 2023 19:43:11 -0800 (PST) MIME-Version: 1.0 References: <20231212044614.42733-1-liangchen.linux@gmail.com> <20231212044614.42733-3-liangchen.linux@gmail.com> In-Reply-To: From: Liang Chen Date: Thu, 14 Dec 2023 11:42:58 +0800 Message-ID: Subject: Re: [PATCH net-next v9 2/4] page_pool: halve BIAS_MAX for multiple user references of a fragment To: Ilias Apalodimas 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" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 34B8780008 X-Rspam-User: X-Stat-Signature: bsxyzqj9iwsb7gcu9a4ztne4usipjojt X-Rspamd-Server: rspam03 X-HE-Tag: 1702525392-846507 X-HE-Meta: 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 h7v2aMFd 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000499, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Dec 13, 2023 at 7:39=E2=80=AFPM Ilias Apalodimas wrote: > > Hi Liang, > > On Tue, 12 Dec 2023 at 06:47, Liang Chen wrot= e: > > > > Referring to patch [1], in order to support multiple users referencing = the > > same fragment and prevent overflow from pp_ref_count growing, the initi= al > > value of pp_ref_count is halved, leaving room for pp_ref_count to incre= ment > > before the page is drained. > > > > [1] > > https://lore.kernel.org/all/20211009093724.10539-3-linyunsheng@huawei.c= om/ > > 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" > Sure. Thanks for the suggestion! > 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 > >