From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Tokarev Subject: Re: *terrible* speed of savevm/loadvm/delvm Date: Sun, 23 Nov 2008 23:08:06 +0300 Message-ID: <4929B826.1020907@msgid.tls.msk.ru> References: <491B0F4B.9060502@msgid.tls.msk.ru> <491C1E8C.3070701@redhat.com> <4925B5C4.1030008@msgid.tls.msk.ru> <49295FED.9020602@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: KVM list To: Avi Kivity Return-path: Received: from hobbit.corpit.ru ([81.13.33.150]:21658 "EHLO hobbit.corpit.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751992AbYKWUIJ (ORCPT ); Sun, 23 Nov 2008 15:08:09 -0500 In-Reply-To: <49295FED.9020602@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Avi Kivity wrote: > Michael Tokarev wrote: >>>> As you see, it writes 2 bytes, llseeks to THE SAME >>>> position, writes next 2 bytes and so on. This takes >>>> HUGE amount of time, and can be done, in most cases, >>>> in a single write without any seeks. [] > Any idea what is happening? Is it disk bound, or cpu bound? Yes, see above. llseek(curpos)+write(2bytes) - try doing that for for a more-or-less large file and you'll see ;) And it seems that this slowness is here for a long time really. It's just that change in default write/cache mode made the problem very obvious. /mjt