From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christian Borntraeger Subject: Re: [PATCH v4] mm: Avoid unnecessary page fault retires on shared memory types Date: Mon, 30 May 2022 11:35:10 +0200 Message-ID: <33fd4731-9765-d78b-bdc3-f8243c98e81f@linux.ibm.com> References: <20220527193936.30678-1-peterx@redhat.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Content-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To:Subject: MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=ng6QDHiym8ko3LZgo1Eo2j/En/Lp09aJGcAb2nd2wNc=; b=DoHbX1AKv3PzHh Z5IwooVtDypB4z9tSLcmmT9e7v7ut4WUCs2F39jmqZXwwVlAJ9xnoFu0T3Tcr2IsF9d2zxFeejBZU bmxvA+lkuFiYZF2+VhGrf+JnKGcfefFWaT8lX1vc5mdqzSQwUagEDfWozmqGN+tJ5Ob+IBIP4xdNi ou78zxkR6+edVvy0H/VgC1iuGd5t7ZTaQdJYwkzjVDLOvaBNza+Qd+sWLvsFA5sHs3ADlUfuCloT1 tZCeAFzhHjC8n/atfVq+LPiGkqEgw83NvVbTOOqCg6WQpgryDITKX0U+Cuwmbrgqn6RMOVPW7VIdX MSpQyboIV4DnA22f0sfA==; DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=message-id : date : mime-version : subject : to : cc : references : from : in-reply-to : content-type : content-transfer-encoding; s=pp1; bh=ZYzW3+GXOL8I0AfUdLsg5MVY8XGCNIfi5dgvNuU6uaU=; b=aJRxENPLxPxtJPLPMpZbZB6ZMNv3yb0g75x/iaJw7LwXznLfzcFFd+VhsSYa4DDin1Og h3EtEuduOMNJdyWcPGf8Bp6j8HIvSzuOxy/3v6U/k2EZA3ai81b28DfbzQAvyLegWbh1 6JeeHGepvOgSmc7L30MoUcRt75rv2HhxbCLI6q4veiPA68Sc+ilz6QI6uDVuislGDiwl YeuRHaNHYRJKefnUIzx1TjXR7BhIi0QNPJjTPVc/RjJeQKBVl5otsnG/aMJgufq14x+Q SfzDBggiNkH6uIogm1bEat+ek9Ln35Wju1AiyyoOtoSpZv9Lk89aLEZ/3hCHMI9fbtzG Eg== Content-Language: en-US In-Reply-To: List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-riscv" Errors-To: linux-riscv-bounces+glpr-linux-riscv=m.gmane-mx.org@lists.infradead.org Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Heiko Carstens , Peter Xu Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Will Deacon , Matt Turner , linux-s390@vger.kernel.org, Andrew Morton , Brian Cain , Borislav Petkov , linux-alpha@vger.kernel.org, Alistair Popple , Jonas Bonn , linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, Michael Ellerman , Stefan Kristiansson , linux-snps-arc@lists.infradead.org, Vineet Gupta , Vasily Gorbik , Vlastimil Babka , Ivan Kokshaysky , Rich Felker , sparclinux@vger.kernel.org, Russell King Am 29.05.22 um 22:33 schrieb Heiko Carstens: [...] > > Guess the patch below on top of your patch is what we want. > Just for clarification: if gmap is not NULL then the process is a kvm > process. So, depending on the workload, this optimization makes sense. > > diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c > index 4608cc962ecf..e1d40ca341b7 100644 > --- a/arch/s390/mm/fault.c > +++ b/arch/s390/mm/fault.c > @@ -436,12 +436,11 @@ static inline vm_fault_t do_exception(struct pt_regs *regs, int access) > > /* The fault is fully completed (including releasing mmap lock) */ > if (fault & VM_FAULT_COMPLETED) { > - /* > - * Gmap will need the mmap lock again, so retake it. TODO: > - * only conditionally take the lock when CONFIG_PGSTE set. > - */ > - mmap_read_lock(mm); > - goto out_gmap; > + if (gmap) { > + mmap_read_lock(mm); > + goto out_gmap; > + } > + goto out; Yes, that makes sense. With that Acked-by: Christian Borntraeger