From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8679A3876DF for ; Tue, 10 Feb 2026 16:27:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770740852; cv=none; b=Trs7GtCtKWuG/2sWilb4RZzcQMxA/un+ep3S3Md+65FHztC95xOithTkL3Gk6kMabVoFMl55rrDfZgaAvu/4XpGX+2RN7qUFO/KxBe/4l2dev04UUR5Q01UAPJrdnQc8bTy+AA55Wxxls82+nCDcUpRX9StwFxGQKpHPtznhoGU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770740852; c=relaxed/simple; bh=/MSTCHcxE8Nw01Q9LAI5luuNkXBrAklEZTjpCbZyUWI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Rjpe0NDTTk9ua+ybcVlCvak0r82WH0Ujfb4dgPQieeK/xCo4gWRLZhgKtV/BBuO+RiSpY+5DNzlo7+/LqjjLV0rvOO2Ph0XuMXmSUkKnUUKzHsGK4ozz5w3obLP+yqqXHPe1mNizaQ93bWtWUalyWm3SjhrTjrVijC7mcc+l+YQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=vvcKPWrp; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="vvcKPWrp" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=8QfAoeexURF3xNLX3k+kUOdLmxKsQpukJ46ztP6jhSE=; b=vvcKPWrpnF0WIX6d6ydro8WGu0 JCIbSgFDOYi5HlN9JCoR9L9ULRPHHccl54Hqmr9aO4zaZONyvUamD5Er53kYH7qCUD5xy8+1ECwSO at0T5nOsyHRdkhzSS2Bop4gfvKrRv6XmHq1PcRHKYiIYJth7zMCa6IOHbGr+i5nRKven3rItjgyh4 rJ5FL78y5C6rWhQdfFVZ3HNE6wOMIkU2FTE0D+gIpyffbelx5vJxEExQRdjw0kQvOfh8VO05OtbfZ tnejMyU3yzXCFRr918Bn2lfZApCUPcbNEuzT8iAzkRsCy+iUEWWNWyTttZvSbsmcCtKaZ8J0112iM mGIO+qTw==; Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1vpqa9-0000000BKsu-2Izr; Tue, 10 Feb 2026 16:27:21 +0000 Date: Tue, 10 Feb 2026 16:27:21 +0000 From: Matthew Wilcox To: Dev Jain Cc: akpm@linux-foundation.org, david@kernel.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, ryan.roberts@arm.com, anshuman.khandual@arm.com, kirill@shutemov.name Subject: Re: [PATCH] mm: map maximum pages possible in finish_fault Message-ID: References: <20260206135648.38164-1-dev.jain@arm.com> <397482e7-3c89-48e5-9e8c-0798ac92cc05@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@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: <397482e7-3c89-48e5-9e8c-0798ac92cc05@arm.com> On Tue, Feb 10, 2026 at 06:58:37PM +0530, Dev Jain wrote: > On 06/02/26 8:52 pm, Matthew Wilcox wrote: > > It's nice that you can construct a test-case that shows improvement, but > > is there any real workload that benefits from this? > > I can try to measure this. But, I constructed that testcase to test the > code path, not to show a perf boost (although the boost is obvious enough > so why not show it). As I say in the description: > > "Align finish_fault with filemap_map_pages, and map as many pages as > possible, without crossing VMA/PMD/file boundaries." > > The patch should rather be seen as an extension to 19773df031bc > ("mm/fault: try to map the entire file folio in finish_fault()"). > The code which my patch removes, was added when the norm was to still > perform per-page fault, the argument being, RSS inflation. > > Perhaps I can polish the patch description so that it clearly mentions > what the objective is. You say "removing code". Diffstat says "no real difference in amount of code". 1 file changed, 38 insertions(+), 34 deletions(-) You're messing with some complex code and you haven't said why it's important for us to spend effort making sure you haven't made a mistake. Please persuade us that this is worth doing.