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Fri, 29 May 2026 10:26:59 +0000 (GMT) Received: from osiris (unknown [9.111.13.205]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTPS; Fri, 29 May 2026 10:26:59 +0000 (GMT) Date: Fri, 29 May 2026 12:26:57 +0200 From: Heiko Carstens To: "Mike Rapoport (Microsoft)" Cc: Alexander Gordeev , Vasily Gorbik , Alexandra Winter , Aswin Karuvally , Christian Borntraeger , Harald Freudenberger , Holger Dengler , Jan Hoeppner , Stefan Haberland , Sven Schnelle , linux-s390@vger.kernel.org Subject: Re: [PATCH 3/6] s390/hvc_iucv: replace get_zeroed_page() with kzalloc() Message-ID: <20260529102657.26496E98-hca@linux.ibm.com> References: <20260528-b4-s390-drivers-v1-0-b7108f54d722@kernel.org> <20260528-b4-s390-drivers-v1-3-b7108f54d722@kernel.org> Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260528-b4-s390-drivers-v1-3-b7108f54d722@kernel.org> X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=QLJYgALL c=1 sm=1 tr=0 ts=6a1969f8 cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=kj9zAlcOel0A:10 a=NGcC8JguVDcA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VwQbUJbxAAAA:8 a=20KFwNOVAAAA:8 a=VnNF1IyMAAAA:8 a=689iU_Db-G2QeZ7t9bIA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-GUID: jD5YS_llqLEqOiMZ0C7OjfEnCkb1jQUu X-Proofpoint-ORIG-GUID: jD5YS_llqLEqOiMZ0C7OjfEnCkb1jQUu X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTI5MDEwMCBTYWx0ZWRfX7T08HgYaRuDd 68pGDcwl3FsJQEqWI6xiI2aVDbNUIxj76fiMwJkRHH0NsCLscrpytcbeKTbQodp9Tpc+fzh81ZH eoON/Th0NI/8yek/ENXp/eCb0RbQ9tAgNVqtUu3wx7gCcO9npy7pDl3YeVdrcKTWWUJqW11T89G Xlb2q4ResYq1KD6do1mFrgAqHx2bJVKg1Uwx+sSJkfAi4rMpL8X0VBgGfzy5MZJ2CqxLeENZeSD weWzrgvz9klab9jTTFeRullS6J2NdjUYHfo8/vm2jEM09E6NJA5sRc3YauYZH2ylrxtoXGC7fxQ UFcfd30iHAkz34n+Mh0qq/pesI0CzmCnCxzNBQJ7NOnTzdpcQ7WDDhwVdKlETlDMgc64whRFQ+i ou30QQ4+ytwS0oqXyY05cXU3GDhGVwl8ZOpf9Gvi/f4IXMBQAXlMZWpydySURKZT4+E3/x/8oy9 zruh5GVuglPAiUnx8nw== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-05-29_03,2026-05-28_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 impostorscore=0 malwarescore=0 adultscore=0 lowpriorityscore=0 phishscore=0 clxscore=1015 priorityscore=1501 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605210000 definitions=main-2605290100 On Thu, May 28, 2026 at 10:09:51AM +0300, Mike Rapoport (Microsoft) wrote: > hvc_iucv_alloc() allocates a send staging buffer for accumulating > outbound terminal characters before they are copied into a separate > IUCV message buffer for transmission to the hypervisor. The staging > buffer itself is never passed to any IUCV function. > > This buffer can be allocated with kmalloc() as there's nothing special > about it to go directly to the page allocator. > > kmalloc() provides a better API that does not require ugly casts and > kfree() does not need to know the size of the freed object. > > Performance difference between kmalloc() and __get_free_pages() is not > measurable as both allocators take an object/page from a per-CPU list for > fast path allocations. > > For the slow path the performance is anyway determined by the amount of > reclaim involved rather than by what allocator is used. > > Replace use of get_zeroed_page() with kzalloc() and free_page() with > kfree(). > > Link: https://lore.kernel.org/all/635405e4-9423-4a25-a6e7-e03c8ea0bcbe@redhat.com > Signed-off-by: Mike Rapoport (Microsoft) > --- > drivers/tty/hvc/hvc_iucv.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) Reviewed-by: Heiko Carstens