From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52583) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Wi4JE-0002gF-I0 for qemu-devel@nongnu.org; Wed, 07 May 2014 12:03:10 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Wi4J8-0004pT-4q for qemu-devel@nongnu.org; Wed, 07 May 2014 12:03:04 -0400 Received: from mx-v6.kamp.de ([2a02:248:0:51::16]:45797 helo=mx01.kamp.de) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Wi4J7-0004pF-RH for qemu-devel@nongnu.org; Wed, 07 May 2014 12:02:58 -0400 Message-ID: <536A592C.6090102@kamp.de> Date: Wed, 07 May 2014 18:02:52 +0200 From: Peter Lieven MIME-Version: 1.0 References: <1399422203-5861-1-git-send-email-pl@kamp.de> <53699FE4.5030004@redhat.com> <536A42B0.1070307@kamp.de> <20140507151938.GG4045@noname.str.redhat.com> <536A50A2.1020008@kamp.de> <20140507153853.GH4045@noname.str.redhat.com> <536A5510.6020406@kamp.de> In-Reply-To: <536A5510.6020406@kamp.de> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCHv3] block: optimize zero writes with bdrv_write_zeroes List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf Cc: famz@redhat.com, qemu-devel@nongnu.org, mreitz@redhat.com, stefanha@redhat.com, pbonzini@redhat.com On 07.05.2014 17:45, Peter Lieven wrote: > On 07.05.2014 17:38, Kevin Wolf wrote: >> Am 07.05.2014 um 17:26 hat Peter Lieven geschrieben: >>> On 07.05.2014 17:19, Kevin Wolf wrote: >>>> Am 07.05.2014 um 16:26 hat Peter Lieven geschrieben: >>>>> On 07.05.2014 04:52, Eric Blake wrote: >>>>>> On 05/06/2014 06:23 PM, Peter Lieven wrote: >>>>>>> this patch tries to optimize zero write requests >>>>>>> by automatically using bdrv_write_zeroes if it is >>>>>>> supported by the format. >>>>>>> >>>>>>> This significantly speeds up file system initialization and >>>>>>> should speed zero write test used to test backend storage >>>>>>> performance. >>>>>>> >>>>>>> Signed-off-by: Peter Lieven >>>>>>> --- >>>>>>> v2->v3: - moved parameter parsing to blockdev_init >>>>>>> - added per device detect_zeroes status to >>>>>>> hmp (info block -v) and qmp (query-block) [Eric] >>>>>>> - added support to enable detect-zeroes also >>>>>>> for hot added devices [Eric] >>>>>>> - added missing entry to qemu_common_drive_opts >>>>>>> - fixed description of qemu_iovec_is_zero [Fam] >>>>>>> >>>>>>> +static BdrvDetectZeroes parse_detect_zeroes(const char *buf, Error **errp) >>>>>>> +{ >>>>>>> + if (!buf || !strcmp(buf, "off")) { >>>>>>> + return BDRV_DETECT_ZEROES_OFF; >>>>>>> + } else if (!strcmp(buf, "on")) { >>>>>>> + return BDRV_DETECT_ZEROES_ON; >>>>>>> + } else if (!strcmp(buf, "unmap")) { >>>>>>> + return BDRV_DETECT_ZEROES_UNMAP; >>>>>>> + } else { >>>>>>> + error_setg(errp, "invalid value for detect-zeroes: %s", >>>>>>> + buf); >>>>>>> + } >>>>>>> + return BDRV_DETECT_ZEROES_OFF; >>>>>>> +} >>>>>> Isn't there QAPI generated code that you can use instead of open-coding >>>>>> this conversion between string and enum values? >>>>> Actually I have no idea. As you pointed out in the qapi patch I sent >>>>> it was quite hard for me to crawl through the whole stuff as one who is not >>>>> familiar with it. Can somebody advise here? Anyhow, I wonder >>>>> how this would work since qapi doesn't know the C Macros. >>>> QAPI does generate C enums, so you should take whatever identifier it >>>> uses instead of defining your own macros. You may need to include >>>> qapi-types.h for this. It also creates a *_lookup array that maps enum >>>> IDs to strings. >>> Ah, cool stuff, thank you. I found the enum and the lookup array, >>> but is there also a function that maps a string to an enum ID? >> I don't think so, but if you need it, you're probably doing something >> wrong because QAPI already calls you with an enum parameter and not a >> char* one. > I am in blockdev_init and want to set dinfo->bdrv->detect_zeroes to > the correct ID. Do you have a fast solution? Everything else in this > function is not using QAPI calls. Actually, there is already a manual parsing for the werror and rerror in this function. I think for the future there might be need for a generic function that maps a string to the ID of an enum object. If you don't have objections I would leave the parsing function as is for the moment. Peter