From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f45.google.com (mail-wg0-f45.google.com [74.125.82.45]) by dpdk.org (Postfix) with ESMTP id C7E795A65 for ; Sat, 11 Jul 2015 17:08:23 +0200 (CEST) Received: by wgmn9 with SMTP id n9so15436553wgm.0 for ; Sat, 11 Jul 2015 08:08:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mirantis.com; s=google; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=a+h+BbL6W90TfPanhFKqblYhuq/BW0outKmYkYGbgfM=; b=g5iap7yOQ2uQnBCw7ChrRoihKz/yeJN0vqzDqMLjBt0FvWOoy9YFzopMyYc6i3heqD c/B3xsqHvJp1h73FyDP7fkopEL6o0SyVelTOfpf833fSxf7h3NibGxe3zOtE4zPyd0Or cEDkdL4ChsTSpSbiO9Pl6uV1maaw7HvCZ+miE= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type; bh=a+h+BbL6W90TfPanhFKqblYhuq/BW0outKmYkYGbgfM=; b=HHk/MQRdNsXT8VBmlORpPysbsYcvLOc9Z8b+TDYkURHb0Zag8yhcEchaoklfT3kITg gJ0eKKotaOtmY62lrrEvqPx90YiaeiFSLCcGpSBIfB5fBAbG+dWIYnnYU0BRi6n6GTs9 FmvXpJlrqghPZhQZLhxLI5bEwefG+ZFaE62F/b4uV5v2MhLNXwpk0okH/IRYK27j3FNw QWjDL3SNJxOIdkYWfDNoAg6wTd7jRdGrFWn0R5ne7Ilav4jTc2bJOk02jlrpi91OyXMG ZU0JHDvnj+swEso58MVFqXG0+N4ARjHtUPga+Hej+BDZsicxW0RrggUKBx8ru4vp6OMk VGrA== X-Gm-Message-State: ALoCoQlFZf31eWQ+96Vy4C8BUNxJjAI5mtIyyRdvKgfR22i+NNIxIQIRYgV7m+LOotMMJ0bAhKVM MIME-Version: 1.0 X-Received: by 10.180.23.33 with SMTP id j1mr7107636wif.44.1436627303588; Sat, 11 Jul 2015 08:08:23 -0700 (PDT) Received: by 10.194.64.102 with HTTP; Sat, 11 Jul 2015 08:08:23 -0700 (PDT) In-Reply-To: References: <1427994080-10163-1-git-send-email-pboldin@mirantis.com> <1429184910-30186-5-git-send-email-pboldin@mirantis.com> <1665929.SfCu3BinAE@xps13> Date: Sat, 11 Jul 2015 18:08:23 +0300 Message-ID: From: Pavel Boldin To: "Xie, Huawei" Content-Type: text/plain; charset=UTF-8 X-Content-Filtered-By: Mailman/MimeDel 2.1.15 Cc: "dev@dpdk.org" Subject: Re: [dpdk-dev] [PATCH v5 4/5] vhost: eventfd_link: replace copy-pasted sys_close X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 11 Jul 2015 15:08:24 -0000 Xie, All, Please find my comments intermixed below. On Fri, Jul 10, 2015 at 6:42 PM, Xie, Huawei wrote: > Don't know why previous mail get messed. > > On 7/10/2015 10:50 PM, Pavel Boldin wrote: > Xie, > > Regarding the patches: > 1. The replaced code in fourth patch is checked to be a copy-paste of the > `sys_close` syscall. > > sys_close does extra cleanup than the replaced coe. My concern is, for > example, sys_close will mark the fd as next-to-be-allocated fd. Will there > be issue when we allocate a new fd, because it will be allocated starting > from the value of next-to-be-allocted-fd? I think kernel willn't blindly > use that value, but not sure. > That is what applications do when call `close' libc function -- the freed FD is ready to be allocated again and it is OK for applications to reuse FDs. > > 2. It is not uncommon for the applications to close FD making it allocated > for a different file. In our particular case the file is closed in the > *source* process and *added* to a target process, so matching fds should > not be the problem. > > Yes, that is exactly what the old code does. > 3. There is an implementation of the exact same thing in the SCM_RIGHTS > [1] that can be used as the reference code. > > I did a rough check. Maybe i miss something. I see it calls fd_install on > a newly allocated fd. That is exactly what i want to replace the current > code with. > Currently we allcoate eventfd in user space and install a new file onto it > through fd_install. Actually we don't need to allocate the eventfd in user > space at all, what we should do is allocate a new fd in kernel, and install > the file onto it. > > new_fd = get_unused_fd_flags(...) > fd_install(new_fd, get_file(fp[i]) > Well, this requires changes from the user-space side so I prefer not to do it by myself at the moment, because I'm no expert in DPDK. I can provide with the updated patches though but I will require a lab to check that it works indeed. No comments below this line. Pavel > > /huawei > > [1] https://github.com/torvalds/linux/blob/master/net/core/scm.c#L248 > > Pavel > > On Fri, Jul 10, 2015 at 5:27 PM, Xie, Huawei huawei.xie@intel.com>> wrote: > On 6/17/2015 11:24 PM, Thomas Monjalon wrote: > > 2015-05-07 06:54, Xie, Huawei: > >> On 4/16/2015 7:48 PM, Pavel Boldin wrote: > >>> + /* Closing the source_fd */ > >>> + ret = sys_close(eventfd_copy.source_fd); > >> Pavel: > >> Here we close the fd and re-install a new file on this fd later. > >> sys_close does all cleanup. > >> But, for instance, if we allocate new fd later, normally it will reuse > >> the just freed fds by sys_close, is there issue here? > > Pavel, Huawei, > > Could we come to a conclusion on this patch series please? > For the previous 3 patches, i am OK except that i don't think inline is > needed explicitly for non-performance critical function. > For this patch, didn't check the fs code. > > > > > > > > >