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[209.85.220.65]) by mx.google.com with SMTPS id t11sor2177182pgs.22.2019.05.21.03.26.20 for (Google Transport Security); Tue, 21 May 2019 03:26:20 -0700 (PDT) Received-SPF: pass (google.com: domain of minchan.kim@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b="d/JcV1xu"; spf=pass (google.com: domain of minchan.kim@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=minchan.kim@gmail.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=v7oTWqJm+U+8EwWIlN8PXARmqW1yabluA4GVB5Q/Ymc=; b=d/JcV1xuIxQEiJwk7yG4v/8OtBPTzjRoH8pRp+ELNSATolCfDK10qD/aK35UikxFIH XeQP6Deb0NOJGW9tREokTHWw5iFX8kZxVfgFeb/CCvMv2F9O3egSSZNvvB7f2WZlGxbI u80t7LgdQY+wj3uWSQsxNk9jKK9aZiyNeusSuazL9BtuzJEfWCE2KkS4J0qf++Sxcpyy m1IVjgGh1hp9/6t4cp2N7Lpabf829ZtUVbTkGefGfgmPgYsZ8w6H0HNRrKvWjWordBwS lwFekyCyWpBkKcRcnAHRnL9rPS9xJITzC59oT29L99JwuLJ/c2TsdbdElO5uRbjpqpiI R+4A== X-Google-Smtp-Source: APXvYqzZdjlSTwRjqi+DHWVHAtfu7VOytFN2Av0aQnixHQc7zc41tJwI2PuEyhis7/e/9mFRwgfs2w== X-Received: by 2002:a63:754b:: with SMTP id f11mr81175818pgn.32.1558434379902; Tue, 21 May 2019 03:26:19 -0700 (PDT) Received: from google.com ([2401:fa00:d:0:98f1:8b3d:1f37:3e8]) by smtp.gmail.com with ESMTPSA id z7sm26834601pfr.23.2019.05.21.03.26.15 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Tue, 21 May 2019 03:26:18 -0700 (PDT) Date: Tue, 21 May 2019 19:26:13 +0900 From: Minchan Kim To: Michal Hocko Cc: Andrew Morton , LKML , linux-mm , Johannes Weiner , Tim Murray , Joel Fernandes , Suren Baghdasaryan , Daniel Colascione , Shakeel Butt , Sonny Rao , Brian Geffon , linux-api@vger.kernel.org Subject: Re: [RFC 6/7] mm: extend process_madvise syscall to support vector arrary Message-ID: <20190521102613.GC219653@google.com> References: <20190520035254.57579-1-minchan@kernel.org> <20190520035254.57579-7-minchan@kernel.org> <20190520092258.GZ6836@dhcp22.suse.cz> <20190521024820.GG10039@google.com> <20190521062421.GD32329@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190521062421.GD32329@dhcp22.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) 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: Archived-At: List-Archive: List-Post: On Tue, May 21, 2019 at 08:24:21AM +0200, Michal Hocko wrote: > On Tue 21-05-19 11:48:20, Minchan Kim wrote: > > On Mon, May 20, 2019 at 11:22:58AM +0200, Michal Hocko wrote: > > > [Cc linux-api] > > > > > > On Mon 20-05-19 12:52:53, Minchan Kim wrote: > > > > Currently, process_madvise syscall works for only one address range > > > > so user should call the syscall several times to give hints to > > > > multiple address range. > > > > > > Is that a problem? How big of a problem? Any numbers? > > > > We easily have 2000+ vma so it's not trivial overhead. I will come up > > with number in the description at respin. > > Does this really have to be a fast operation? I would expect the monitor > is by no means a fast path. The system call overhead is not what it used > to be, sigh, but still for something that is not a hot path it should be > tolerable, especially when the whole operation is quite expensive on its > own (wrt. the syscall entry/exit). What's different with process_vm_[readv|writev] and vmsplice? If the range needed to be covered is a lot, vector operation makes senese to me. > > I am not saying we do not need a multiplexing API, I am just not sure > we need it right away. Btw. there was some demand for other MM syscalls > to provide a multiplexing API (e.g. mprotect), maybe it would be better > to handle those in one go? That's the exactly what Daniel Colascione suggested from internal review. That would be a interesting approach if we could aggregate all of system call in one go. > -- > Michal Hocko > SUSE Labs