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[194.45.78.10]) by smtp.gmail.com with ESMTPSA id qq12-20020a17090720cc00b0099d0c0bb92bsm1538009ejb.80.2023.08.18.12.59.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 18 Aug 2023 12:59:40 -0700 (PDT) From: Jesper Dangaard Brouer X-Google-Original-From: Jesper Dangaard Brouer Message-ID: <107f67de-da5a-766b-1cb9-b107f407831b@redhat.com> Date: Fri, 18 Aug 2023 21:59:38 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Cc: brouer@redhat.com, netdev@vger.kernel.org, vbabka@suse.cz, Eric Dumazet , "David S. Miller" , Paolo Abeni , linux-mm@kvack.org, Andrew Morton , Mel Gorman , Christoph Lameter , roman.gushchin@linux.dev, dsterba@suse.com Subject: Re: [PATCH net] net: use SLAB_NO_MERGE for kmem_cache skbuff_head_cache To: Jakub Kicinski , Jesper Dangaard Brouer References: <169211265663.1491038.8580163757548985946.stgit@firesoul> <20230818092612.74025dc7@kernel.org> In-Reply-To: <20230818092612.74025dc7@kernel.org> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 826D6140019 X-Stat-Signature: fkfc7pnokzdis3upiy3pugt35p7khzoe X-HE-Tag: 1692388784-675915 X-HE-Meta: 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 HzJBbWAh PMMiyO4A9U+E1/c8f1QM4dOPHTBOVJ8COSx8KewM+Tg/PfoCjQv6XMM9ys2v24oXjUDycyAninGYIwz5X/JY2trXCJSlNaq36Kv0SWgPrVbIENYAJ+z0PIeSc/vSbp5avFbHAirwchracRcPLYV2dBtzNIlhuzfQCC/k5dkN+8WQOgf7E6de3dnzt3fqlO6nk28lu94ZZaiV+C2bORxdFc58xQaKsonj3PMpKE43Y3ImreSduKQrGahmMYPmiUzI0L8WF9gZQgdCN1lxCEu1xyQTDecAmXvgXg0MCQhQglaqlTxMMMY25O/3YkfTzGp/LIVYvuXinq3ahGqTrOTkpBeVinLKDDgouILyxZ99GbFZF+CGCsxGEB7/lfwh03HtUa84frGmDhgY/TvmELn2NQxqKDzE/nSSW8eKslRJG0LT9JZX5PsndzJqLfitFbLvMRxk3n8zXiHPqy0nI5KgyUtAFeLq7vesjgwqf7xC6gzMFv9U= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 18/08/2023 18.26, Jakub Kicinski wrote: > On Tue, 15 Aug 2023 17:17:36 +0200 Jesper Dangaard Brouer wrote: >> Subject: [PATCH net] net: use SLAB_NO_MERGE for kmem_cache skbuff_head_cache > > Has this been a problem "forever"? > We're getting late in the release cycle for non-regression & non-crash > changes, even if small regression potential.. > This patch is not dangerous ;-) SKB slab/kmem_cache is already almost always "no_merge" (due to the flags it uses), but certain kernel .config combinations can cause it to be merged (with other 256 bytes slabs). I happen to hit this config combination in my testlab, and noticed the problem slight performance impact. If anything this patch makes it more consistent. --Jesper