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[47.55.120.4]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-8846e469825sm1235856d6.15.2025.11.19.11.06.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 19 Nov 2025 11:06:02 -0800 (PST) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1vLnVC-00000000bQB-0jDl; Wed, 19 Nov 2025 15:06:02 -0400 Date: Wed, 19 Nov 2025 15:06:02 -0400 From: Jason Gunthorpe To: "Li,Rongqing" Cc: Leon Romanovsky , "huangjunxian6@hisilicon.com" , "linux-rdma@vger.kernel.org" Subject: Re: [????] Re: [PATCH][v2] RDMA/core: Prevent soft lockup during large user memory region cleanup Message-ID: <20251119190602.GN17968@ziepe.ca> References: <20251113095317.2628-1-lirongqing@baidu.com> <20251117174738.GE17968@ziepe.ca> <02011baf337649f6997166f223417417@baidu.com> Precedence: bulk X-Mailing-List: linux-rdma@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: <02011baf337649f6997166f223417417@baidu.com> On Wed, Nov 19, 2025 at 02:03:20AM +0000, Li,Rongqing wrote: > > > Fix soft lockup issues by incorporating cond_resched() calls within > > > __ib_umem_release(), and this SG entries are typically grouped in 2MB > > > chunks on x86_64, adding cond_resched() should has minimal > > performance > > > impact. > > > > This is not true, I think this should have been more careful to only resched > > after larger groupings.. How much slower did you make normal 4k unpins?? > > > > Jason > > > I don't see this as a issue for several reasons. First, this code > path is not performance-critical. Yes it is! > Second, the number of cond_resched > calls added by this modification is identical to what was introduced > in commit 928da37a229f3444, No its not! That loop does entire batches of pages into a PAGE_SIZE memory buffer, this does it for every single 4k page. > any problems. Third, as seen in commit 16c610162d1f1c, the > cond_resched call rate was reduced to once every 16 packets - our > current frequency remains well below this commit. I don't know what that has to do with anything here Jason